Energy Conservation In Housing, entire book, Text Only (No Graphics copied on this web-site)

[Energy Conservation in Housing]

ENERGY
CONSERVATION
IN
HOUSING

A Collection of Data on
Energy-Efficient Housing Approaches

David L. Meinert

++++++++++++++++
NOTE: This Google “blog” did NOT put any of the drawings / graphics
necessary to
understand a lot of the information.
However, I have the complete (PDF) and Word documents of the text and
graphics
on this site. Go to “Home” of this site, and look at “Files” which
lists the book text in PDF format, as well as additional files on
other insulation and energy saving topics.

I also have the complete (PDF) documents of the text and graphics
on a Yahoo web-site.
The Yahoo site includes some photos of an attic and basement
insulation project. Use this link to connect to it.
http://groups.yahoo.com/group/EnergyConservationHousing
(Expect to have to sign in to the Yahoo group to access the data.)
Starting in November 2008, this data has been available on a different
site (“Multiply.com”).
http://energyconshousing.multiply.com/
The main improvement on this Multiply site is the ability to add
videos. I added some insulation videos that can be viewed on the
Multiply site. The Word and PDF documents are also on this site.
However, my home computer has been unable to open those documents on
the Multiply site due to some problem with “JavaScript.” If you run
into similar problems, the best source for the complete PDF and Word
documents is on the above Yahoo site.
Expect to have to “sign-in” to the Multiply site to access the data.
Previously the text Word and PDF documents on the Multiply.com site
were on an MSN site. http://www.msnusers.com/EnergyConservationInHousing
The MSN sites was closed in February 2009.
++++++++++++++++




The printed version was published by Vantage Press New York / Los
Angeles
in 1990 and re-printed in 1992. As of 1996, it was out of print.
This electronic version was re-edited in 2003





The following is the narrative that was printed on the back cover of
the original book, published in 1990 and re-printed in 1992.

$13.95

ENERGY CONSERVATION
IN HOUSING
A Collection of Data on Energy-Efficient
Housing Approaches

By David L. Meinert

In these days of soaring energy costs, it is the rare person indeed
who has not given some thought to how he or she can make this one
necessity of life more affordable. Once one has done the obvious –
keep the temperature down, not leave appliances on needlessly, et
cetera – what then? Prevention – that is, design of housing to
accommodate energy efficiency – is the answer. “But isn’t that
expensive?” you might ask. As David L. Meinert asserts in Energy
Conservation in Housing, it will be more expensive not to seek ways of
making your home more energy-efficient.
This book demonstrates in layman’s terms the principles of energy-
efficient housing so that you can get the most for your energy dollar
by designing and constructing a house using these principles or
modifying your current home. Basic types of heat loss and gain and
types of insulation, approaches for optimum energy efficiency in
building design, and ways to improve the supply of fresh air in
tightly constructed energy-efficient homes are the main topics
addressed. The many diagrams included and lengthy list of resources
will assist the reader in exploring energy conservation further.

About the Author

David L. Meinert, born in Quincy, Illinois, is a clinical optometrist
who accumulated his knowledge of energy conservation as a result of
several years of independent study. He is a graduate of Rock Valley
College, Northern Illinois University, and the Illinois College of
Optometry and is a former Army Optometrist.
Dr. Meinert currently resides in Herndon, Virginia, with his wife,
Lora.

Vantage Press, Inc.
516 West 34th Street, New York, N.Y. 10001

(The publisher no longer has any copies of the actual printed book.
It has been out of print since 1996.)







All persons making use of the information contained herein are
reminded that this information is intended to provide guidelines.
While much effort have been made to ensure this information is
accurate, the author makes no representation and gives no warranty
that this information, if used, will provide the energy savings
described. Much of this information is based on data from the
original 1990 and 1992 printings. Only some of the data has been
updated since then. The author assumes no responsibility whatsoever
for any loss or damage resulting from the use of any of this
information.
In a sense, this text can never be completely “finished” since
knowledge is always changing and expanding. (Certainly my time is
limited as to how many topics I can continue to research and update.)
However, the technology for insulation and ventilation is probably
over 90% complete at this time, so there is much to be gained by
understanding and utilizing the data in this text.






Copyright 1990 by David L. Meinert
Printed in 1990. Re-printed in 1992.
Original Published Text Printed by
Vantage Press, Inc.
516 West 34th Street,
New York, New York 10001

Original Published Text
Manufactured in the United States of America
ISBN: 0-533-08331-1

This book is out of print as of 1996.

Contents


Introduction . . . . . . . . . . . . . . . .
vi

Acknowledgments . . . . . . . . . . . . . . .
vii
Technical conditions or problems with this electronic
version . . . viii

Part One. Energy Fundamentals: The Road to
Understanding Energy-Efficient Housing
Insulation and Energy
Efficiency . . . . . . . . . . .
1
Basic Information on Heat Loss and
Gain . . . . . . . . . 1
Vapor
Barriers . . . . . . . . . . . . . . . . .
6
Window Orientation and Energy
Efficiency . . . . . . . . 9
Radiant
Barriers . . . . . . . . . . . . . . . .
16
Infiltration of Outside
Air . . . . . . . . . . . . .
19
Development of Energy-Efficient
Homes . . . . . . . . . 22
Analysis of Energy-Efficient
Homes . . . . . . . . . . . 23

Part Two. Superinsulation: The Energy-Efficient Solution
Why
Superinsulation? . . . . . . . . . . . . . .
29
Resolving Vapor Barrier and Insulation
Problems . . . . . . 29
Heat Loss
Calculations . . . . . . . . . . . . . .
35
Shape of the Building and Heat Loss and
Gain . . . . . . . . 42
Thermal Mass and the Drop of
Temperature . . . . . . . . 43
Heating
System . . . . . . . . . . . . . . . . .
44
Cooling Tubes for Summer
Cooling? . . . . . . . . . . 48
How Much Insulation Is Actually
Needed? . . . . . . . . 51
Heating Costs for the
Year . . . . . . . . . . . . .
54
Applications of Energy Technology to New
Homes . . . . . . 58
Retrofitting Insulation in Existing
Homes . . . . . . . . 74

Part Three. House Ventilation:
Fresh Air for Tightly Constructed Homes
Evaluating Air-to-Air Heat
Exchangers . . . . . . . . . . 82
Summary of Data on Commercially Available Heat
Exchangers . . . 88
Air-to-Air Heat Exchangers: List of Selected Commercial Companies
91
Air-to-Air Heat Exchangers: Homemade
Models . . . . . . . 96



Part Four. Additional Data on Energy-Efficient Housing
Comparative Costs of
Insulation . . . . . . . . . . .
111
Assembling Superinsulated
Walls . . . . . . . . . . . 115
Vapor Permeability of
Materials . . . . . . . . . . .
116
Selecting the Appropriate Overhang for South
Windows . . . . 119
Design Temperatures for Heating and Cooling for Selected Locations
122
Percentage of Sunshine for Selected
Locations . . . . . . . 124
Ground Temperatures in Shallow
Wells . . . . . . . . . 125
Magnetic Variations from True
North . . . . . . . . . 126
Winter Solar Gain and Deviation from
South . . . . . . . 126
Solar
Position . . . . . . . . . . . . . . . .
127
Clear-day Solar Gain for Double-glazed
Windows . . . . . 128
Moisture Condensation within Sealed Panes of
Glass . . . . . 129
Other Energy-saving
Ideas . . . . . . . . . . . . .
132

References . . . . . . . . . . . . . . . . .
135
Related
References . . . . . . . . . . . . . .
138
House Construction
Information . . . . . . . . . . . 139
Manufacturers and Product
Suppliers . . . . . . . . . 140

Index . . . . . . . . . . . . . . . . . . .
145
Appendix:
Retrofitting basement
insulation . . . . . . . . . . 147
Getting started on retrofitting and existing
home . . . . . 150
Practical data on retrofitting basement floor
insulation . . . . 151
Observations on vapor barrier
effectiveness . . . . . . 152
Attic radiant
barrier . . . . . . . . . . . . .
152
Air-to-air heat exchanger – Update
information . . . . . . 153




Introduction


This book is a collection of data on energy-efficient housing from a
wide variety of sources. It is intended to provide an overview to
help the reader gain knowledge and a better understanding of how to
reduce energy costs in housing.
Around 1980 I became interested in learning more about energy
conservation in housing construction when I was looking at designs of
homes. Since then I have collected data from a variety of sources on
energy-efficient housing as a hobby in my spare time. Most of this
book is a compilation of data I had obtained from 1980 through 1990.
While much of this data is “old” it still has substantial practical
applications. Although my usual occupation is unrelated to the topics
in this book, I found most of the data on energy-efficient housing can
be understood and utilized without prior training and experience.
Energy-efficient houses need not be complicated or unusually
expensive. When properly designed, they can serve to cut costs of
heating by 90 percent compared to energy use prior to 1970. A
properly designed energy-efficient house uses only about one-third of
the heat in winter as compared to houses with normal levels of
insulation. The energy savings in summer will also have significantly
reduced cooling costs.
I have tried to condense pertinent data from many sources. With this
information it is possible to gain a good understanding of energy
conservation and to apply these concepts in the design and
construction of future homes and the modification of some existing
homes.
Part One explains basic concepts in heat loss and gain and the types
and forms of insulation. Part Two explains approaches for optimum
energy efficiency in building design. Part Three explores ways to
improve the supply of fresh air in tightly constructed energy-
efficient homes. Part Four contains additional data to help the
reader better utilize energy efficiency principles. The references
list the many sources of this book and related topics for readers who
desire further information. Listed after the references are
manufacturers of some products described in this book. The last 7
pages (the Appendix) include additional practical details on home
insulation.







Acknowledgments

This book was produced by a compilation from many sources. Every
effort was made to give credit to the original source of the
information. Since these data were collected for many years, I am not
certain of the exact source of all pieces of data. Some of the data
were obtained from friends and experiences over the years.
The listed references will help the reader to gain more detailed
information on topics presented here. During the past twenty-five
years much work has been done to better understand how to conserve our
world's energy reserves and at the same time to make energy costs in
homes more affordable. Much credit is due the energy consultants,
home designers, and previous authors who have discovered and presented
this information in earlier publications.
I owe special thanks to William A. Shurcliff and Ed McGrath for
technical advice and helpful discussion on some of the topics covered
in this book. I am especially appreciative to Elise W. Mackie for
extensive editing contributions prior to submission of this text for
publishing.
This book was originally produced (around 1988) at home through the
capabilities provided by the Macintosh™ 512K Enhanced home computer,
by Apple ® and was printed on the Apple Laserwriter ™ to produce
camera-ready copies for the published pages. The published book was
out of print as of 1996.
The initial documents to produce this book were created on the
Macintosh (text by MacWrite program and diagrams by FullPaint
program). In 2002, I converted these documents into Word on the
Macintosh, then using the MacDrive 2000 program, was able to convert
the documents into Word 97, readable by Windows 98 computer systems.
I continued with editing work on the text and diagrams in 2003.

Technical conditions (or problems) with this electronic version.

The first procedure you should do is to make a back-up copy of this
text. It’s only about 4 MB, so it won’t take up much space on your
hard drive. If you have the capability, next time you back-up your
hard drive documents to a CD-R, save a copy of this document on the
CD.

Symbols. The main symbol I use in the text is “Delta” – used
typically for “change” as in “change of Temperature” or “Delta
T” (∆T). Delta is a triangular-shaped symbol (∆). That is how it
displays on my Window 98 PC. However, on my old Windows 95 laptop,
the Delta symbol comes out as a “square” shape, instead. If I then
open that document on the Windows 98 PC, the “Delta” symbol displays
as a triangle, which is the usual Delta shape.

Are there any blank pages? When I formatted this document, I selected
“page break” from the “insert” menu (I selected “break” then clicked
“page break” and “OK”) where I wanted the pages to end. This makes
the page numbers correspond to the Table of Contents and Index.
Depending on how your PC formats the pages, that spacing might be
off. You could end up with “blank” pages, and then none of the page
numbers would agree with the Table of Contents and Index. That would
then require a lot of work “re-formatting” either the text font
(typically I used “Times New Roman” font) or you could change the
margins, under “page setup.” Since it is electronic, you can find
what you want by using “Find” under the “Edit” menu.

Are columns of data out of alignment? Depending on how your computer
formats the text you could end up with data in some columns that are
out of alignment, due the tab settings and font size interacting
differently than how I formatted the columns.

Are there any problems visualizing the diagrams? Of the numerous
diagrams within the text, some are whole-page diagrams and others are
smaller. There is typically a short delay before the actual diagram
displays (even though the text around it immediately displays). I
have had occasions where a previously present diagram is “missing”
from the page. I then click where the diagram should be, and a
rectangular frame appears where the diagram should be, but still no
diagram. I then “double-click” in that rectangular frame, and a
“picture” is now displayed in a full-size “window.” This display is
only the picture, no longer the regular text version of the diagram.
Simply “close” this window, by clicking the second square (with an “x”
in it) at the upper right corner of the screen. The picture /
“object” should now appear in a rectangular place on the screen, where
it was initially missing. If that doesn’t work, then go to your “back-
up” copy of the document, and go to that same position in the text.
When you see the correct diagram, highlight it (put the cursor on the
diagram, and press the left mouse button), then copy it (press the two
keys “Ctrl” and “c” – or select “Copy” from the “Edit” menu). Then
return to the original document with the missing diagram, highlight
it, press “backspace” then paste the replacement diagram in that
position (press the two keys “Ctrl” and “v” – or select “Paste” from
the “Edit” menu). Then “save” the document.
If the diagram shape / size gets distorted, it is possible to “reset”
the diagram. Select the diagram (put the cursor on the diagram and
press the left mouse button). Under the Format menu, select “Object,”
then select the “Size” tab, then click “Reset” and “OK.”


Part One
ENERGY FUNDAMENTALS
The Road to Understanding
Energy-Efficient Housing
Insulation and Energy Efficiency

Since the oil embargo of 1973, increased emphasis has been placed on
energy savings. Although the crisis is considered behind us, the
amount of available energy is not unlimited. With the rising price of
energy, more efforts have been made to conserve energy use for heating
and cooling buildings. While it is possible to enhance the energy
efficiency of existing buildings, it is easier to incorporate energy
saving techniques in new construction.
Insulating walls and ceilings is a well-known approach to conserving
heating and cooling costs of a home. Most houses built prior to the
early 1970s usually did not have insulation in the walls and had only
a small amount of insulation in the attic.
Today most housing codes mandate minimum levels of insulation
required in walls, ceilings, and floors for new construction.
Buildings insulated to current standards of construction provide
significant energy savings compared to most older buildings.
By incorporating current energy conservation knowledge into housing
design it is possible to build homes that require little conventional
heating. A highly efficient home can be economically heated during
winter in some of the coldest climates of the United States and
Canada. Such highly energy-efficient homes have even greater value
when energy prices rise; as fuel prices increase, heating costs for
poorly-insulated houses might increase by hundreds of dollars while an
energy-efficient house might have increased heating bills by only one-
tenth as much.

Basic Information on Heat Loss and Gain

Heat flows from warm objects to colder objects. The flow of energy
is measured in British thermal units, or BTUs. One BTU is the energy
required to heat one pound of water by one degree Fahrenheit. The
rate of heat flow depends on two factors: the temperature difference
(∆T) and the resistance to heat flow (R-value). Materials of high R-
values retard the flow of heat better than materials with low R-
values. 1
Various parts of a building have different rates of heat loss. By
adding insulation heat loss is slowed down, but not stopped. The
overall heat loss from a surface is measured by its heat transmission
(the "U-factor") or, more commonly, by its overall resistance to heat
flow (the "R-value"). The R-value and U-factor are inversely related.
1

These formulas demonstrate the relationship between the U-factor, the
R-factor, and the rate of heat loss from a surface.

U = 1 for a surface
R
Heat loss ( in BTU/hr) = U x Area ( in square feet) x ∆T
( in degrees Fahrenheit)

∆T (or "Delta Tee") = Inside to outside temperature difference
(°F.)

An uninsulated wall (R-4) loses heat more than three times faster
than a wall with standard levels of insulation (R-13). A
superinsulated wall (R-40) loses heat three times slower than a
standard insulated wall.
There is a tenfold reduction of energy loss from an uninsulated wall
(construction prior to 1970) to a superinsulated wall today. The
purposes of making a home well insulated are to reduce heat loss, save
energy costs, and make the building more comfortable.

Types of insulation

Fiberglass and rock wool (R-3 to 3.5 per inch). These mineral wool
insulations are made from the raw materials sand, glass, slag, and
stone. They are the most commonly used insulations. Fiberglass is
available in rolls, batts, loose fill, and rigid boards, with or
without a vapor barrier. Fiberglass and rock wool are fire-resistant
and moisture-resistant. They are irritating to skin, eyes, and lungs;
thus proper protection should be used during installation. 1, 2
Cellulose (R-3.8 to 4.2 per inch). This is shredded paper, treated
to be fire-retardant. Cellulose is an excellent insulator. Available
as loose fill. 1
Vermiculite and perlite (R-2.3 to 2.7 per inch). These are pellets of
light, expanded mineral material. Perlite and vermiculite are cheap
and easy to use, but with problems of moisture retention and
settlement. Available as loose fill. 1
Polystyrene. This is foam made from expanded plastic. Polystyrenes
are usually sold as rigid boards: beadboard (R-4) and Styrofoam
(R-5). Polystyrenes are reasonably moisture-resistant. Since these
foam products are flammable, they must be covered with a fire-
resistant substance, such as wallboard. Styrofoam typically has a
small amount of freon in its matrix, raising its insulative value
higher than that of beadboard. Beadboard is also termed expanded
polystyrene since beads of the expanded plastic are fused together.
Styrofoam is termed extruded polystyrene; it is tightly formed into
its final shape and results in greater strength than beadboard.
Freon is typically used in the manufacturing of most foam products.
Chloro- and fluoro-carbons, such as freon, cause damage to the ozone
layer of the atmosphere. Unlike the fluorocarbons used in extruded
polystyrene, expanded polystyrene releases the hydrocarbon, pentane,
during its manufacturing and curing process.
As of 2003, several versions of polystyrene are now available that do
NOT use or release volatile organic compounds (such as pentane) or
chloro- or fluoro-carbons (such as freon). (I found sources for CFC-
Free polystyrene by an Internet search using the words: polystyrene
insulation cfc-free.)

Isocyanurate and urethane (Thermax, R-Max [R-7 to 9, per inch]).
This is another form of foam insulation. Isocyanurate and urethane
are very effective insulating materials. They are moisture-resistant
and highly flammable, requiring a fire-resistant covering.
Isocyanurate and urethane foams have freon trapped within the foam
matrix. Since freon conducts heat less well than air, these foams are
better insulators. 2 With aging, the freon escapes, losing up to 20%
of its insulative ability in the first year. While the initial
insulative value per inch can be up to R-9, eventually the
isocyanurate and urethane foams may reduce to R-5.
Phenolic foam insulation (R-8.3 per inch). This is a type of closed
cell foam from chemical polymers. The foam reportedly does not lose R-
value over time, yet has about the highest R-value available. It is
quite fire-resistant and supposedly can even serve as a firewall. 3
Over time, due to water absorption, phenolic boards have apparently
caused cases of severe metal corrosion in roofing. Also, over time
this board was found to have significant shrinkage, reducing its
effective insulative ability. 43
Reflective foil (R-2.4 to 4.4 per surface). When facing an air space
of three-quarters of an inch or more, reflective foil is rated at
R-4.4 when reflecting down, R-2.4 when reflecting up, and R-3 when
reflecting horizontally. Reflective foil acts as a "radiant barrier"
to reflect back the heat waves of far-infrared thermal radiation.
Reflective insulation is of value in keeping such heat waves inside
homes in winter and may have greater value in keeping heat radiation
out of homes during hot weather. 4
Foam-in-place insulation is injected into closed wall cavities to
insulate previously uninsulated walls; it includes the following
types:
Urea formaldehyde (R-4.5 per inch): This foam was suspected of
producing dangerous formaldehyde gases and was banned in 1982 by the
U.S. Consumer Product Safety Commission. The ban is now lifted, but
urea formaldehyde is no longer a popular insulation. Urea
formaldehyde is flammable.
Tripolymer® foam (R-4.8 per inch) is a phenolic foam injected into
closed wall cavities, but does not have the gas emission problems of
the urea formaldehyde foams. It has significant vapor permeability
(perm of 15) thus needs a vapor barrier for protection from household
moisture. Tripolymer foam is fire-resistant.
Air Krete (R-3.9 per inch) is a foam that is composed of concrete and
air (95% air, thus no heavier than other blow-in or foam insulation).
Since it is made from concrete, it has extreme fire-resistance. 5
Urethane foam (R-7.7). Urethane expands excessively when foamed in
place and can rupture cavity walls. It also shrinks somewhat as it
cures. Urethane is flammable.

Forms of insulation

Rolls. These are blankets of insulation previously cut by the
manufacturer to specific thickness and width and sold in a rolled up
bundle. The width is made to fit between 16 or 24 inch stud spacing
(e.g. One size of roll insulation expands to 6 inch thickness. It is
23 inches wide, and 40 feet long). The insulation is cut to the
length needed by the installer.




Batts. These are insulation blankets that are cut by the manufacturer
to the usually needed lengths as well. Typically, five batts may be
sold in a rolled up bundle. Each batt has a specific dimension (e.g.
3.5" x 15" x 92") so as to fit in the space between studs. Such a size
would be used when the 2 x 4 wall is framed with studs spaced every 16
inches, with a final ceiling height of 8 feet. The installer needs
only to unroll the batt, put in place in the framed cavity, and staple
in position (with no cutting needed except for irregular spaces).
Loose fill. This insulation is composed of small particles or shreds
of insulation either poured or blown into open cavities. There may be
some tendency for the loose fill to settle. The machines for blowing
the insulation in place will break up the compressed insulation, fluff
it, and then blow it through a hose to the desired location. Loose
fill fiberglass and rock wool may cost slightly less for the same
volume of insulation than in rolls or in batts. Blowing insulation
works best with two installers, one to feed the blowing machine and
one to direct the hose around in the attic. Free use of a blowing
machine is often provided after purchase of a quantity of loose fill
insulation. Loose fill has some advantages in that it can fill in
irregular spaces with no additional work. Roll or batt insulation
must be cut for irregular shapes. Most blow-in insulations tend to
settle over time. A special adhesive (Blow-in Blanket®) can be mixed
with blow-in insulation to cause it to bind together. This prevents
later settling. 5 Blow-in Blanket is designed for use in retrofitting
insulation into existing walls.
Rigid boards. These are used for insulating basement or foundation
walls, as a layer within walls or roofs, or used as external sheathing
in new construction.
Reflective foil. Radiant barriers come in many forms: 1) foil bonded
to Kraft paper (single- or double-sided foil covering); 2) foil bonded
to polyethylene bubble sheets (single-sided foil or double-sided foil,
with single or double plastic bubble packs between the foil); 3) foil
bonded to asphalt material; 4) foil bonded to a polypropylene web;
and 5) foil covering sheathing board. Perforated foil allows water
vapor transmission, while still blocking radiant heat. Other forms of
radiant barriers are also available. Foil is bonded to other
materials because it is too fragile alone, unless it is made thick
(and thereby more expensive). Since a radiant barrier blocks radiant
heat, its effective insulative value is significantly higher than its
"R-4.4" rating under conditions of heavy solar radiation. Reflective
foil bonded to bubble sheets has a high insulative value (up to R-14,
reflecting downward).
Foam-in-place. Useful for filling in irregular spaces or for
insulating inaccessible areas or enclosed spaces. Foaming is a tricky
process and uses expensive equipment. Some of the foams have been
implicated in producing toxic vapors, resulting in severe indoor air
contamination. Before having a house foamed, the consumer should
investigate the specific manufacturer's product.


Insulation Summary

Raw Forms R-Value
Insulator material available per inch Problems

Fiberglass Glass Blankets 3.0 - 3.5 Absorbs water
Sand Batts
Loose fill
Boards

Rock wool Slag Blankets 3.0 - 3.5 Absorbs water
Rock Batts
Loose fill

Cellulose Paper Loose fill 3.8 to 4.2 Absorbs water

Vermiculite Mineral Loose fill 2.3 to 2.7 Absorbs water
Perlite

Styrofoam Petroleum Boards 5 Flammable

Beadboard Petroleum Boards 4 Flammable

Isocyanurate Petroleum Boards 5 to 9 Flammable,
Urethane emits cyanide gas
when burning

Phenolic foam Chemical Boards 8.3 Availability, shrinkage;
polymer due to water absorption,
it can rust adjacent metal

Reflective foil Aluminum Rolls Reflects radiant Fragile,
Sheets heat, R-2.4 or needs
more for one protection
surface

Urea- Chemical Cavity fill, 4.5 Gaseous emissions,
Formaldehyde polymer squirted into wall flammable,
spaces (resembles shrinkage,
shaving cream special equipment
until it sets)

Air Krete Cement, Cavity fill, 3.9 Special equipment,
air pumped into wall availability
spaces

Tripolymer Chemical Cavity fill, 4.8 Special equipment,
foam polymer squirted into wall availability
(phenolic foam, spaces (resembles
fire-resistant) shaving cream
until it sets)

Blow-in Blanket Special Blown into wall 4.1 Special equipment,
adhesive, after being mixed availability
loose fill with insulation
insulation

Vapor Barriers

What are vapor barriers, what are they for, and how do they function?

Vapor barriers are membranes or films used to prevent the movement of
water vapor from one side of the membrane to the other side. They
serve to keep moisture out of insulation and out of walls, floors, and
ceilings. Adding insulation without a vapor barrier (or putting the
vapor barrier on the wrong side of the wall) can damage the frame of
the house seriously.
Why is this? Just as heat flows from a warm place to a cool place,
so also vapor flows from where there is more vapor to where there is
less. Warm air can hold more water vapor than cool air. The inside
air of the house has more moisture in winter that the outside air.
The inside moisture tries to move to the outside. The moisture
travels through all materials porous to vapors. It travels through
the wallboard into the wall. As the vapor passes through the wall,
it reaches colder temperatures. Some of the moisture condenses on the
cold surfaces within the wall and freezes during the winter.
Insulation can hold the moisture in place all year, since walls have
little ventilation. Over the years the wall studs and siding can rot,
slowly destroying the building. Attics can escape the severe
consequences of condensation and thawing if there is adequate
ventilation. If not, the ceiling can be damaged from condensed water
running throughout the attic. Furthermore, insulation loses much of
its heat-retaining ability when wet and will slump and degrade if it
gets wet enough.
To prevent such condensation disasters, vapor barriers are used on
the warm side of the wall. That means that the vapor barrier should
be closest to the living areas of the internal home.

Inside relative humidity and vapor barriers

It is common that older homes use a humidifier in winter to add
moisture to the air. Homes equipped with a vapor barrier do not have
an air dryness problem; rather, the home tends to get too humid during
winter. The vapor barrier prevents the moisture from passively
diffusing into the wall. The vapor barrier protects the insulation,
protects the wall, reduces air infiltration, reduces heating costs,
eliminates the need for a humidifier, and may make it necessary to
remove moisture in winter instead of adding it.

Types of vapor barriers

Roll and batt insulation can be obtained with or without a vapor
barrier. Vapor barriers (when sold attached to insulation) have a
paper- or foil-coated facing with a tar-like material (i.e., asphalt)
under the paper. These vapor barriers usually slow down the
penetration of moisture enough to protect the insulation. To be
properly effective, the vapor barrier seams should be overlapping and
taped at the joints so that the moisture will not penetrate into the
wood framing and wet the framing or insulation.






A better approach is to have a continuous plastic membrane covering
the inside of the living areas. All joints of the plastic membrane
(vapor barrier) should be sealed. However, there will be far fewer
joints to seal with a continuous film (10 feet by 50 feet in size, or
larger) than there would be with all the individual vapor barriers
from each insulation batt. The typical vapor barrier material is 6
mil polyethylene, a plastic film that is 0.006 inches thick. Visqueen
is one brand of polyethylene. The 6 mil thickness is reasonably
sturdy and should withstand some abuse during installation. To
provide a smooth surface for attachment of the wallboard, the
insulation batts are typically stapled to the inside face of the studs
and only the polyethylene vapor barrier covers the stud surface to
which the wallboard is attached.
A vapor barrier can be made by sealing the edges of foil-covered
sheathing boards. Reasonable vapor barriers can be formed by use of
certain paints on the internal wall surface that significantly reduce
moisture penetration (e.g., Glidden "insulaid"). In new construction
a continuous polyethylene vapor barrier, applied prior to putting up
the wallboard, is preferable.





Limitations of vapor barriers

It is difficult to make a vapor barrier perfect. However, if the
vapor barrier is installed properly, it will protect the framing and
insulation from moisture and the damage it can cause. A properly
installed continuous vapor barrier will also block nearly all leakage
of outdoor air into the house, greatly reducing the space heating
demand for the house. However, even with a carefully applied vapor
barrier, there will be some moisture penetration through nail holes
and small tears. As occupants of the home hang pictures and mount
recessed lighting fixtures there will be new breaks in the vapor
barrier.
Vapor barrier tests from Sweden show that polyethylene can become
brittle and crack in as little as five years. Ultraviolet (UV) light
causes polyethylene to degrade. Thicker polyethylene is more
resistant to UV degradation, and reportedly black polyethylene is more
resistant to UV degradation than clear polyethylene. A thin layer of
polyethylene can degrade in as little as one year when exposed to
direct sunlight. Polyethylene degradation primarily occurs while the
material is exposed to sunlight during construction. After
construction, the polyethylene is safely within the wall and protected
from direct exposure.

Loss of vapor barrier integrity causes significant problems, since the
vapor barrier is needed for the life of the house. A polymer vapor
barrier has been developed in Sweden that resists degradation (TenoArm
® film) and is expected to last for the life of the house. 3 TenoArm
film is 8 mil thick and uses higher-quality raw materials with added
ingredients to stop degradation. It is slightly thicker than the
polyethylene conventionally used in house construction. See the
product information section after the references for more information.

Vapor problems with external insulative sheathing

A problem can occur when a standard wall is made with insulation and
vapor barrier and then external insulative sheathing is applied.
Often the insulative sheathing is foil-backed or polyethylene-coated,
making an excellent vapor barrier on the cold side of the wall. The
proper position for a vapor barrier is on the warm side of the wall.
Furthermore, some foam boards perform reasonably as a vapor barrier.
If the inside vapor barrier is not sealed substantially better than
the outside sheathing, there will be significant condensation over
time, wetting the insulation and rotting the wall. Since there is
little ability to ventilate an enclosed wall, it is important to
either have the external sheathing and siding vapor-permeable or have
sufficient gaps for the vapor to pass through the exterior of the
wall. There are some types of vapor-permeable foam insulation boards
that are designed to prevent condensation within the wall. An open
cell foam board, faced with perforated radiant barriers, will not
induce condensation if properly installed.

Window Orientation and Energy Efficiency

While much has been said about insulation in recent years, more can
be said of the significance of solar orientation of windows and the
resultant effect on the energy requirements of the building.
Windows serve to let in passive solar energy, dependent on their
orientation to the sun. Plenty of sun in winter can reduce the
heating bills of the building. Plenty of sun entering a home in
summer will tend to make the building less comfortable and will
significantly raise the cooling bill when air conditioning is used.
The key to controlling the sun's effect on home heating and cooling
costs due to windows is understanding how solar orientation of windows
results in solar gains for specific seasons and using that knowledge
to plan the layout of the building to optimize solar gain in winter
and minimize solar gain in summer. This is most easily done prior to
construction.


The sun's path in summer and winter.


The sun's altitude above the horizon is higher in summer. In winter,
the sun is low and to the southern sky. The change in the sun's
rising and setting direction causes east and west windows to get too
much direct sunlight in summer when the heat is not needed. South
windows get heat when needed (winter) and little heat when not needed
(summer). Redrawn from Home Energy for the Eighties, copyright by
Ralph Wolfe and Peter Clegg, published by Garden Way Publishing,
Pownal, VT 05261.

In winter the sun rises in the southeast, travels across the southern
sky, and sets in the southwest. Windows facing south will capture the
winter sun nearly the whole day and provide passive heating of the
building. East and west windows receive less than 50% of the solar
heat in winter compared to south windows. North windows receive no
direct sunlight in winter. Flat roof windows gain a small amount of
solar energy in winter.
In summer the sun rises in the northeast, travels nearly overhead,
and sets in the northwest. South windows receive very little direct
sunlight in summer. A properly sized overhang can prevent all direct
summer solar gain from south windows. North windows receive a small
amount of morning and evening sunlight in summer, but that heat gain
is relatively slight.
East and west windows receive their greatest solar gain in the heat
of the summer. East windows receive full solar exposure most of the
morning, and west windows receive full solar exposure most of the
afternoon. Even a very wide overhang would not completely shield the
east and west windows from the summer sun. External awnings or
external louvers are necessary to block a significant amount of the
solar gain from east and west windows in summer. Although internal
shading of east and west windows has some value in reflecting heat,
most of the unwanted solar gain has already gotten inside of the
building. Aluminum foil or other highly reflective films attached
directly to a window can block nearly all of the solar gain, but will
make the window significantly darkened or unusable for outside
viewing. Roof windows have their greatest gain in summer. Sloping
south windows also have substantial solar gain in summer.


Solar gain and loss through windows



Clear-day solar gain for windows of various orientations at 40° north
latitude. Gain and loss curves are calculated for double-pane windows
in various months of the year. The heat loss curve is representative
of 6,300 degree-days for Denver, Colorado. The net gain is the
difference between the gain and loss curves. South-facing windows
provide solar heat in proportion to seasonal heat demands. Other
window orientations provide more solar heat in seasons when it is not
needed. Statistical data are derived from Designing and Building a
Solar House and The Passive Solar Energy Book. Graph format is from
the Solar Energy Handbook.

For south windows to receive the full amount of winter exposure to
the sun, the south side should be free of obstructions, such as
buildings and trees that block solar gain. Even the branches of
deciduous trees could block excessive amounts of needed solar gain for
south windows during winter. A properly designed overhang shades
south windows in summer, while allowing full solar gain in winter.
Trees on the east and west are beneficial in providing summer
shading.

Summary: South-facing windows gain heat when needed (winter) and gain
little when not needed (summer). North windows have little gains year
round. East, west, and flat roof windows gain only a small amount of
sunlight in winter and gain a lot of solar heat when not needed in
summer. Gain from sloping south windows is actually dependent on the
angle of tilt. When facing closer to vertical, the gain is similar to
typical south windows; when facing closer to horizontal, they provide
less winter gain.



Most climates in the United States need heat in winter and should
avoid gaining heat in summer. South windows provide passive solar
heat when needed and avoid it when not needed. In a climate requiring
summer air conditioning, the objective is avoidance of the summer
sun. This means minimizing east, west, and roof windows as well as
skylights. In place of skylights it is possible to install vertical
windows high in the wall or ceiling (clerestory windows),6 preferably
facing south. These overhead windows will provide a better balance
of natural lighting without the summer solar gains associated with
roof or sloping windows. By opening clerestory windows during warm
weather, the homeowner allows the warmest air to passively leave the
home, drawing in cooler air from other windows. A fan mounted in a
clerestory window, actively exhausting the hottest air, could take the
place of a ceiling mounted whole-house exhaust fan.




How much is enough? (south-facing windows)

Since south-facing windows provide heat when needed (winter) and
provide little heat when not needed (summer), the more south windows a
building has, the better . . . . correct? Not quite so . . . .
Large amounts of sunlight can pass through windows. Additionally,
there is significant heat loss through windows. Single-pane windows
(R-0.89) lose 14 times as much heat as the same size of normally
insulated wall (R-13). Double-pane windows (R-1.84) lose seven times
as much heat as a normally insulated wall (e.g., 14 square feet of
double-glazed window area loses as much heat as 100 square feet of
wall area). Even triple-pane glass (R-2.79) loses almost five times
as much heat as a normally insulated wall. When compared to a
superinsulated wall (R-40), windows become a major cause of heat loss
for a building.

If there is a large amount of south-facing glass, the solar gain on a
clear winter day can cause the inside building temperatures to rise
uncomfortably high; the interior will quickly get cold as night
descends. A large amount of window space results in large daily
temperature fluctuations.
South-facing glass area should not exceed 6 to 8% of the total living
area in an energy-efficient home or overheating problems can occur if
special precautions are not taken.6 A home of 2,000 square feet size
should have a maximum of 120 to 160 square feet of south windows.

Window insulation

A single pane of glass has significant heat loss when the inside to
outside temperature difference is great. It would seem a simple
matter to add additional layers of glass to get extra insulative
value. A second pane of glass reduces the heat loss about 50% by
adding an insulating air space. Triple-pane glass has only one-third
the heat loss of single-pane glass.
Each layer of glass reflects or absorbs about 14% of the solar energy
striking it. Therefore, a single-pane transmits about 86% of
sunlight. Double-pane glass transmits about 74% and triple-pane glass
transmits about 64% of the solar energy reaching the outer pane of
glass. The advantage of adding more layers of glass has a point of
limited benefits; the additional panes of glass save more heat, yet
they cost more to install and block some of the solar radiation.
Movable insulation placed over windows during cold nights reduces
heat loss while allowing maximum heat gain during daylight hours.
Langdon 7 analyzed heat loss and gain through windows in various
winter climates and found the following:
1. Triple-pane is better than either double- or single-pane glass in
very cold climates for all window orientations.
2. In milder climates, south-facing windows perform slightly better
with double-pane than triple-pane glass, although all other window
orientations are usually better with triple-pane glass.
3. Using window insulation (R-5 or more) at night, double-pane
performs similar to, or slightly better than, triple-pane for south
windows. For all other orientations it is usually better to have
triple-pane with movable insulation.
4. Using window insulation during cold nights improves thermal
performance of all the windows types analyzed.

To be effective, the insulation must be put in place after dark and
removed in the morning. Due to cost and labor of installation as well
as the daily handling needed, window insulation is typically omitted.


Window-framing materials

In recent years, double-pane windows have become fairly standard in
new construction. Double-glazing is mandated by many building codes.
While double-glazing cuts window heat loss in half, the material
holding the panes in place is also quite important when considering
the insulative value of the window.
Wood, rigid vinyl, and fiberglass framing conduct heat at nearly the
same rate. Metals (e.g. steel and aluminum) conduct heat one thousand
times faster than wood or vinyl. 8 A wood or vinyl window frame
conducts heat less readily than the glass it supports. Metal frames
of windows will conduct heat many times faster than the glass they
support. For this reason, metal window frames not having an internal
thermal break will condense water vapor at a very low inside relative
humidity. From the inside of the house these metal frame windows
will seem to be nearly at outside temperatures. In winter this can be
like having a piece of ice sitting inside your windowsill.
Careful designing and more expense are required for metal windows to
be made with an internal thermal break. The thermal break occurs by
attaching the external aluminum frame to a nonconductive material
(e.g., wood or plastic) and the other side of the window frame
continuing with metal or wood framing. A metal frame having a thermal
break does not insulate quite as well as a nonconductive frame.
Another way of having a thermal break is attaching an exterior metal
storm window to a nonconductive window frame.

Number of windowpanes and inside condensation

Assuming that the window frame is less conductive than the glass,
i.e. wood, vinyl, fiberglass, or metal frame with a thermal break,
condensation will occur on the inside windowpane before the frame.
This condensation will occur at a specific level of inside relative
humidity.
Condensation on inside pane of glass. Since the additional air spaces
in multiple-pane windows add insulation, the inside pane of glass
stays warmer and condensation on its surface does not occur until
higher inside relative humidity levels. Window condensation occurs on
the inside pane of glass at the below listed percent (%) inside
relative humidity (RH) level for various types of windows (single-,
double-, triple-, and quadruple-pane glass). The temperature of the
inside pane of glass in degrees Fahrenheit (°F) is listed with the
percentage of relative humidity (% RH). A colder temperature of
inside glass means inside moisture will condense at a lower percentage
of relative humidity. The inside house temperature is seventy degrees
Fahrenheit (+70° F.) in all examples.



Table derived from The Superinsulated House, by Ed McGrath.

Triple-pane windows do not insulate well compared to a normally
insulated wall. However, they do allow the building to have a
reasonable level of inside relative humidity at very low outside
temperatures without causing unnecessary condensation on the windows.

Multiple-pane window designs

In older homes, double-glazing took the form of storm windows that
were put on in winter. Newer storm windows are attached directly to
the framing of the original window. The new storm windows can often
seal better than the older (inside) windows they cover. Any moisture
that leaks around the inside window stands a chance of condensing
between the two panes, since the moisture gets trapped there. For
this reason, weep holes are sometimes placed low in the storm window
frame to allow any condensed moisture to leak out.
Manufactured double-glazed windows are made with two panes of glass
sealed together in a frame separated by an insulating air space; there
is no ventilation between the panes. Manufacturers will often put
desiccant crystals in the spacer bars between the two panes of glass
to absorb moisture that gets around the inside pane. If the window is
subjected to excessive humidity levels and the inside pane develops a
poor seal, condensation will eventually occur between the panes.
Homemade window designs should seal the inside pane as perfectly as
possible; the panes external to the inside pane should be vented to
the outside to prevent any water vapor from condensing between the
panes. 2

Smart windows and smarter windows

Special treatment in the manufacturing of windows can reduce heat
loss. Coatings used in low emittance windows reduce heat loss by
reflecting heat waves back inside the house that would otherwise
radiate outside. Additionally, the coatings reflect away excessive
heat in summer. The low-E windows apparently reduce heat loss by 50%.

In the late 1980s a clear glass material was designed that offered
more than three times the insulating value of low-E glass. The
material called Aerugel provided more insulating value in one inch
(R-20) than a six-inch fiberglass batt (R-19). Aerugel was made of
silicon dioxide (found in sand) similar to ordinary glass. Aerugel
obtained its superior insulating ability by trapping air molecules in
microscopic spaces within its matrix. Aerugel is actually a
microscopic skeleton of silica (5% of its volume), the remaining 95%
of the space of Aerugel is trapped air.
The manufacturer (Quantum Optics Company, Emeryville, California) had
planned to make windows with a half-inch plate of Aerugel between two
panes of glass. This would have an R-10 insulation value and will be
almost as clear as triple-pane glass. 9 (Author’s note in 2003:
Aerugel has apparently never been added to the market for window
insulation. So Aerugel is only a theoretical type of window
insulation.)

Radiant Barriers

Heat loss or gain happens in three ways: convection, conduction, and
radiation. Convection occurs by the movement of heat contained in
moving fluids; that is, moving air or moving liquids transfer heat as
they flow from one position to another. Convective heat losses from a
building are stopped by windows, walls, ceilings, insulation, and
infiltration barriers. Conduction is the transfer of heat from one
object to another by direct contact of the two objects. Conductive
heat losses are blocked by reducing framing conduction between the
inside and outside surfaces and by sandwiching insulation between
framing layers. Dead air spaces in insulation will slow down
conduction and convection. Radiant heat travels through open spaces
and through many materials as infrared thermal radiation. Radiant
barriers serve a valuable function in reflecting away unwanted
radiant heat in hot climates. A radiant barrier is a reflective
metallic film, usually aluminum foil on a backing material. The
barrier has two features: high reflection and low emission of radiant
heat. With radiant heat blocked, a building has lower cooling costs
and becomes much more comfortable for the occupants. Radiant barriers
also reduce heat loss in winter. Eighty percent of radiant heat passes
through most building materials and ordinary insulation. A single
layer of a reflective barrier blocks 95% of the radiant heat striking
it. Additional layers of radiant barriers block only the 5% that
passes through the first barrier. Radiant heat gain and loss make up
a significant proportion of total cooling and heating demands.
Current research indicates that in open, uninsulated spaces radiating
heat is responsible for over 60% of the heat transfer. Convection and
conduction account for the balance of the heat transferred. When
insulation and a vapor barrier are used, heat conduction and
convection are minimized. A properly installed radiant barrier blocks
most of the radiant heat. A vapor barrier, a radiant barrier, and the
proper level of insulation block heat transfer optimally. Foil must
reflect into an air space to function as a radiant barrier. Without
an air space, the foil will conduct heat to other surfaces and not
serve as a barrier. The proper sized air space for a reflective
barrier is at least three-quarters of an inch.




In a study of ceiling solar gain in summer, a radiant barrier
combined with R-11 insulation performed thermally as well as R-30
insulation, during peak sunlight hours. Similarly, R-19 with a
radiant barrier gained less than half the heat compared to R-19 alone,
during peak sunlight hours. 10 For summer use, radiant barriers make
their biggest thermal contribution during times of high solar
radiation and less contribution after sunset. Since radiant barriers
are far less expensive than such comparable amounts of insulation,
they become an economical means of reducing heat gain in summer.
Radiant barriers can be installed in attics, in walls, and in floors
over crawl spaces.
Most radiant barriers are also good vapor barriers. To prevent
moisture condensation, such barriers should be installed in a position
suitable for a vapor barrier (when used in insulated spaces). A
perforated radiant barrier allows moisture to escape. In new
construction, the radiant barrier can be draped over the top chord of
the roof trusses before applying the plywood sheathing or attached to
the underside of the top chord. In the draping technique, the foil is
made to sag between the rafters to supply the needed reflective air
space. Radiant heat passing through the roof is stopped by the
barrier. Radiant heat warms the air space above the foil. The
accumulated heat leaves the attic through ridge vents and gable vents
in the attic. Retrofitting radiant barriers can be done by attachment
to the underside of the roof rafter. Reportedly, dust covering a
radiant barrier reduces its insulative value somewhat. For this
reason, double-sided foil has advantages: initially both sides of the
radiant barrier function fully. The side facing up reflects away
radiant heat; the layer facing down does not emit heat. Over time,
the layer facing up loses effectiveness as dust covers it. The layer
facing down continues to function fully.

A radiant barrier beneath the roofing material will raise the roofing
temperature a few degrees. It is believed that this temperature
increase will accelerate the aging of roofing material. One roofing
manufacturer contends that installing a radiant barrier effectively
voids the warranty on their roofing material. By using plentiful
attic ventilation above the radiant barrier, overheating of the
roofing material can be minimized. Provide continuous soffit vents
and use ridge and gable vents to insure proper ventilation.



Cautions on radiant barrier sales

Radiant barrier companies market products that have up to six layers
of foil, spaced to fill 2x6 inch or 2x4 inch framing cavities. They
claim superior insulating properties over standard insulation and
absence of the moisture damage properties of standard insulation.
Some companies appear to indicate that standard insulation is not
usually needed with proper use of foil layers.
Since a radiant barrier blocks 95% of radiant heat, leaving only 5%
of the radiant heat to be stopped by additional layers, what purpose
are the other five layers serving? Mainly they function as dead air
spaces to slow down heat conduction. This is precisely what standard
insulation does more effectively. Installed in the space provided by
a 2x6 inch ceiling joist, six layers of foil are rated by its
manufacturer 11 as R-12 for heat flow up and R-24.2 for heat flow
down. One layer of foil is rated by the same manufacturer as R-3.4
for heatflow up and R-12.4 for heatflow down. An R-19 insulation batt
filling the 2x6 inch space, combined with one layer of foil, results
in R-22.4 for heat flow up and R-31.4 for heat flow down.
Substituting the five additional foil layers instead of standard
insulation is less effective; batt insulation provides a much better
series of dead air spaces than five layers of foil. A single layer
radiant barrier blocks 95% of heat radiation; the conventional
insulation slows heat convection and conduction. Effective thermal
performance occurs if one radiant barrier is combined with the needed
amount of conventional insulation.
Much confusion surrounds the current knowledge of radiant barriers.
It may take years before the facts of radiant heat are known. In the
meantime, the buyer should be cautious.


Infiltration of Outside Air

In many houses there is a significant amount of leakage of outside
air. The outdoor air leaks into the house through any crack or
crevice of the wall, floor, or ceiling or the air passes directly
through porous wall sections. This leakage of outside air into a
building is referred to as infiltration. When driven by even mild
winds (fifteen miles per hour), a conventional home can undergo one to
four complete changes of air in one hour.1 Infiltration makes a house
feel drafty and uncomfortable in winter and significantly increases
the heating bill, since heated air is forced out with infiltration.
Exfiltration is the term describing heated air forced out of a
building.
By contrast, a well sealed home can undergo one air change in two
hours (one-half air change per hour). With the use of a continuous
vapor barrier surrounding the living area and properly sealed doors
and windows there can be less than one air change every 12 to 24 hours
(less than 0.1 air changes per hour).
In the early years of energy efficient buildings, reduction of
infiltration and improvement of the level of insulation made homes far
more economical to heat. Before long it was found that there were
side effects of having a home extremely well sealed. The first
effect, obvious within hours, is the tendency for water vapor to
collect inside the home. High water vapor content in the air can be
suspected when moisture condenses on double-pane windows. Other side
effects occur over time as the occupants breathe contaminants and
germs trapped in stale inside air.
Such indoor air pollution is typically worse than outdoor air
quality. The pollution can come from a variety of sources: carbon
monoxide from incomplete combustion of stoves or heaters, carbon
monoxide and other by-products from smokers, chemicals emitted from
new building materials, excessive water vapors, radon from the soil
and some masonry building materials, and other miscellaneous
contaminants. Radon, a dangerous radioactive gas from uranium, can be
present in soil anywhere. As well as getting into some building
materials, it can enter homes through foundation cracks, porous
cement, sump pump drains, pipes entering the foundation, and well
water. A thoroughly ventilated crawl space below a well-sealed floor
eliminates most sources of radon entering the house. Radon is second
only to smoking as a cause of lung cancer. 12 If the degree of
infiltration is less than 0.25 to 0.5 air changes per hour, then the
building will tend to have a higher concentration of contaminants than
is healthy. Infiltration is the only source of fresh air in
conventional homes. Forceful winds cause fast rates of infiltration;
minimal winds result in too little infiltration. Therefore,
infiltration is not a reliable way to get a consistent supply of fresh
air even in conventional homes. Infiltration with conventional homes
is related to the speed of the wind, not to the amount of contaminated
air.
It is necessary to have a good vapor barrier to keep moisture from
condensing inside the insulation of walls, floors, and ceilings. A
properly installed vapor barrier will block much of the infiltration.
It may then be necessary to ventilate the house to provide the needed
fresh air.


Ventilation

Ventilation means bringing fresh air into a building and exhausting
the stale air to the outdoors in a controlled fashion. Fresh air is
easily provided by opening windows, which increases the heating bill
and causes drafts in cold weather. Another approach is to bring
outside air in through the furnace cold air duct, allowing the air to
be heated on its way inside the house. Specific areas of the house
should be ventilated to remove moisture, odors, and contaminants.
Usually the kitchen, laundry room, and bathrooms should have air
exhausted to the outdoors. Exhaust fans have a difficult time
getting enough replacement air to vent adequately in a tight house.
Instead of opening a window to feed the exhaust fan, it is preferable
to provide the needed fresh air using a special type of whole-house
ventilator.

The air-to-air heat exchanger

A whole-house ventilation system provides fresh air while stale air
is exhausted. All exhaust air is vented to one point and fresh air is
brought in at another point. By bringing hot stale air in close
proximity to the incoming cold fresh air, it is possible to exchange
the heat between the two streams of air. In this way, the outgoing
air heats the incoming air. Since this heat is extracted from the
outgoing air, it is a way to get fresh air without having to heat the
air to reach room temperature. Such a device is known as a Heat
Recovery Ventilator (HRV) or perhaps more descriptively as an air-to-
air heat exchanger.



Having a slow rate of continuous ventilation will provide fresh air
as well as exhausting contaminants from the house. The efficiency of
the heat exchanger is a measure of its heat recovery capability. The
efficiency rating can range from 50% to 90% in models commercially
available. It is also possible to construct a homemade heat
exchanger, although it takes a significant amount of work. The
commercial exchangers tend to be somewhat expensive, although they pay
back the cost over time when compared to merely opening a window for
ventilation or having leaky doors or windows to allow infiltration. A
properly arranged vent plan for an air-to-air heat exchanger places
exhaust ducts in the bathrooms and kitchen while providing fresh air
ducts for all other rooms. This could eliminate the need for
individual bathroom and kitchen exhaust fans; the heat exchanger fans
remove contaminated air and supply fresh air. Another approach is to
route the exhaust fan ducts from the bathrooms and kitchen into an
exhaust air chamber, which then leads into exhaust chamber of the air-
to-air heat exchanger.

Air supply ducts can be made by use of inside wall, ceiling, and floor
cavities or by putting actual ducts through these spaces, depending on
requirements of the local building code. Initially it was felt that
supplying fresh air at one point in the house would allow even
ventilation. Although this may work for open floor plans, individual
rooms do not receive an adequate supply of fresh air.
It might seem a good idea to add the fresh air to the cold air inlet
of the forced air heating system. There are two problems with this:
1) The fan power of the furnace is much stronger than the heat
exchanger fans. This would cause a tremendous imbalance of the
airflow through the exchanger. 2) In an energy efficient home, the
forced air ventilation system runs so infrequently that it would not
adequately circulate ventilation air. Some heat exchanger companies
recommend turning the forced air fan to the "on" position whenever the
exchanger is operational so that fresh air from the heat exchanger is
properly distributed. This technique will suffice, but much
electricity is required for the frequent operation of the high-powered
furnace blower. In the long run, it is more cost-effective to install
fresh air ducts for the heat exchanger vent system instead of using
the ducts of the heating system to mix the fresh air within the
house.
If one retrofits a heat exchanger in an existing house, duct booster
fans mounted in the forced air heating system ducts could be used to
provide adequate mixing of the house air. Duct boosters have low power
consumption (e.g. 25 watts for 200 cubic feet per minute airflow); if
strategically placed in the heating ducts, two of these fans operating
continuously might provide adequate mixing of house air. The duct
boosters could maintain continual airflow throughout the house, mixing
the air without continual operation of the high-powered furnace
blower.

Infiltration barriers

There are a number of brands of housewraps designed to reduce
infiltration into houses. These infiltration barriers are thin
plastic sheets made from a fine pattern of polymer fibers. The tight
weave blocks air from blowing through the housewrap film, yet the
films are readily permeable to vapors, allowing any trapped moisture
to escape through the barrier. Tyvek ® was the first brand of
housewrap and has a perm of 94. With this high permeability, it
readily allows moisture to pass through.
Typically, the low-cost housewraps can be purchased in either a 3- or
9-foot width. With standard insulated walls, such housewraps cut heat
loss by 29% to 33%, as shown in independent laboratory tests using 2 x
4 inch frame walls with 3.5" (R-11) insulation in a 15 mile per hour
wind.14 The heat savings occur by blocking infiltration and by
keeping cold air out of the insulation, to maintain its full thermal
performance. Infiltration barriers are installed on the outside of the
wall between the sheathing and the siding. Vapor barriers are put on
the inside of the wall. If the vapor barrier is continuous, then
infiltration is not a problem. If a continuous vapor barrier is
provided, housewrap products still have a function by preventing cold
air from blowing into the insulation. The insulation retains its full
thermal value when covered exteriorly with a housewrap.
Commercially available housewraps are: 1) Tyvek; 2) Rufco-Wrap; 3)
Barricade Building Wrap; 4) Airtight-Wrap; 5) VersaWrap; and 6) Tu
Tuff Air Seal.15


Development of Energy-Efficient Homes

Over the years people have discovered that modifications of standard
insulation levels can cause dramatic savings in the energy costs of
keeping a home at comfortable temperatures. The thousands of dollars
spent achieving a special design can pay monthly dividends by reduced
energy costs. Such building types have been termed solar homes, earth
homes, envelope homes, and superinsulated homes. All incorporate
features to reduce the energy demands for heating and cooling. These
types of homes have outstanding thermal performance. Some owners of
these houses claim that they rarely need additional heat to keep the
house comfortable in winter, since the homes require only small
amounts of heat at specific times. The energy-saving houses have
advantages that justify slightly higher construction costs.
Earth homes reduce energy demands by having a substantial amount of
the house underground. The south side of the earth home is usually
exposed to the sunlight to take advantage of passive solar energy.
Since underground temperatures do not change as much as the outside
air temperature, the earth home can achieve a more stable internal
temperature. Insulation below ground is still required since the
earth is not as warm as needed for normal living conditions.
Solar homes seek to capture the energy of the sun by the passive
means of sun entering through windows or active means of solar
collector plates absorbing heat or converting sunlight to
electricity. Active collection is a complex and costly process.
Passive solar homes collect heat through properly placed windows; the
resulting heat of the sun is stored in the mass of the building.
The envelope home has been described as "a house within a house."
The envelope house is passive solar. It has some of the advantages of
an earth home since it is usually built partly into the ground. The
envelope home uses double walls on the south and north sides of the
house. A complete envelope of circulating air is present with
envelope homes since the attic space and the crawl space beneath the
home connect the air spaces in the north and south walls. As the sun
enters the south windows, it heats the air in that space. The heated
air automatically rises, traveling into the attic. The solar heat is
transferred to the mass of the internal house it surrounds. As the
air cools, it travels in the air space along the north wall. The path
of the air is completed by returning through the crawl space. The
south side of the house is usually made into a large sunspace, an
enclosed sun porch.
Superinsulated homes have a design of exterior walls, floor, and
ceiling to allow very little heat loss. South-facing windows provide
passive solar gains. The home does not need to be underground, nor
does it require a sunspace to function. Plans for superinsulated
houses usually incorporate an air-to-air heat exchanger.


Analysis of Energy-Efficient Homes

Energy efficient home types result in less utilization of space
heating either by decreased heat loss or by harvesting other available
energy. An obvious disadvantage of energy saving homes is the
additional expense of the planning and construction. Energy efficient
homes as well as many conventional new homes result in poor indoor air
quality. For this reason, extra ventilation must usually be added.

Earth-sheltered home

Earth-sheltered homes use the earth to moderate temperature extremes.
Outside air has seasonal changes in temperature from -30°F to over
+100°F in some areas of the United States. The ground near the
surface changes in a similar way to the air temperature. However, the
ground temperature seven feet below the surface of the earth stays
within a twenty degree range year-round throughout most of the United
States. In winter, the ground is warmer than the air; in summer, the
ground is cooler than the air. While the earth is not warm, it
certainly has less extreme temperature differences than above ground.
The exterior of earth homes is usually insulated to levels between
R-30 for parts of the home near the surface and R-10 for parts of the
house deepest in the ground.

Earth-sheltered home


The moderating effect of the surrounding earth decreases the heating
and cooling requirements to minimal levels. With most of the home
substantially underground, there is minimal heat loss in winter.
Since there is south-facing glass, the windows gain passive solar
heat.

The cooling effect of an earth home makes summer performance very
hard to match. In summer, the cooler surrounding earth will offset
the gains of heat from the air temperature. The cooling effect may be
partially due to the absence of radiant solar heat; solar radiation is
unable to pass through two feet or more of the earth covering the
home. The thick layer of soil absorbs the solar radiation so it
cannot reach the dwelling, making an earth home feel cooler than
conventional homes.
A good moisture seal on the outside of the building is very important
since all exterior surfaces could allow water to enter the home. The
walls and ceiling must be constructed much more solidly than in
conventional homes due to the massive weight of earth. Such homes are
impractical where the ground is very moist, having a high water table,
or very cold, such as where permafrost exists. Earth homes work best
when built into a south-facing slope, but can also be built on flat
land.

Solar home

Solar homes capture the heat of the sun by passive gains and/or by
active collection. Passive solar heat is transferred to the mass of
the house by the sun shining directly on heat absorbing masonry floors
and walls (e.g., Trombe Walls) and by having the passively heated air
circulate throughout the house by fans. Active solar systems absorb
the heat of the sun in specially designed collectors and transfer it
to a heat storage chamber (rock bin, water tank, or other storage
medium) or actively collect solar energy by photovoltaic cells.

Solar home




Instead of going through extreme means to reduce heat loss, solar
homes seek to collect the needed amount of solar energy and use it
from storage as required. Thermal mass is an important feature of
passively heated solar homes. The received sunlight is stored in
walls and floors capable of holding much heat. The heat-holding
capability of such masonry walls and floors prevents overheating
during the heat-up phases and allows a slow release of the heat during
times when sunlight is not plentiful.
Active solar systems are very expensive, requiring a very long time
before energy savings equal initial costs. Active solar homes require
a fairly large area of south-facing roof for solar collection and
sufficient inside space for storage of the heat.
Passive solar houses require extensive amounts of south-facing
glass. Heavy masonry surfaces are needed for thermal storage of the
collected solar energy. During prolonged periods of cold, the large
glass area loses considerable amounts of heat. The stored heat may
not be sufficient for the building needs because of rapid heat loss
through the large window areas. In the final analysis, when the
temperatures drop very low, thermal mass is not adequate.

Envelope home

Envelope homes entered the energy efficient housing market in the
late 1970s and the early 1980s. It is a home connected to the earth
by a circulating envelope of air. It is passive solar and passive
cooling and has no moving parts except for vents that are open or
closed depending on the season. The home performs thermally so well
that it quickly gained recognition for its energy savings. This
seemed to be the design for all sensible homes.
Why did the house perform so well? First of all, the house has two
sets of standard insulated walls on the north and south. The east and
west walls are well insulated or superinsulated. Both the ceiling and
the roof are insulated separately. The attic air plenum is insulated
from all sides. Twice the amount of insulation of a conventional
house is used. There is a moderating effect of the earth in the
crawl space below the house, providing some heat storage. There is
lavish use of windows on the south side. This solarium, or sunspace,
is a very attractive feature of the envelope house. The envelope home
is far beyond conventional houses in energy conservation.
There are still many strong advocates of envelope homes, yet the
popularity of these homes has declined somewhat over the years.
Enthusiastic owners are convinced that the houses have the best living
conditions possible, although they admit it has a higher cost than the
superinsulated design.



The envelope home is more labor-intensive to build than some other
types. The double north wall is difficult to construct. There is a
potential chimney effect: if a fire starts in the outer envelope, it
can be fed by a circulating stream of continuously available air.
There can be a significant problem in meeting some local fire codes.
Extra labor is necessary for insulating both sides of the air plenum
along the south walls, in the attic plenum, and in the north walls.
The house tends to collect stale air in the inner home. However, the
occupants can ventilate the inner house to the envelope for fresh air,
since the outer envelope often gets enough infiltration.



It is claimed that solar heat gained in winter is stored in the mass
of the house, but the opposite can be shown by calculation. The heat
enters the outer envelope, and due to the cold outdoor temperatures,
more of the heat escapes outdoors than is absorbed into the house. At
least two-thirds of the solar gain is lost before it has the chance to
be absorbed into the mass of the house. Metz suggested it would be
more efficient to have the sunspace connected with an insulated heat
storage chamber below the house and to eliminate the vast plenums
surrounding the house, with air circulated by a thermostatically
controlled fan.17 It would cost far less and function much more
effectively than the air envelope surrounding the house.
Shurcliff was also not convinced that envelope homes were the best
design.18 While the homes perform well, they are expensive to
construct and have potential fire problems with the air plenum and the
heat storage means are ineffective. Much of the received heat leaves
the structure through the vast expanses of glass used in the outer
south walls. He suggested that heat storage is far more effective
using other means. Shurcliff recommended that air circulation could
be accomplished more economically by use of fans and ducts instead of
by the large air plenums.


Claims were made for the superior insulating effect of the double
wall design (an inner R-11 wall and an outer R-19 wall). However,
when comparing that to a single superinsulated wall (of R-30 value),
the plenum space in between can be shown thermally to make no
significant difference.

Heat loss calculations for the attic of the envelope home during a
winter day. The outside temperature is 0° during the day and the
inside is 70°, attic temperatures are 100°, roof insulation R-19,
roof heat loss area of 1,450 square feet, ceiling insulation R-13,
ceiling area of 1,000 square feet. There is 100° ∆T (temperature
difference) from the attic plenum to outside (100° - 0° = 100°).
There is a 30° ∆T from the attic plenum to the inside of the house
(100° - 70° = 30°). The roof heat loss is 7,630 BTU/hr ( 1/19 x
1,450 sq ft x 100° ∆T = 7,631 BTU/hr). The heat lost through the
ceiling (transferred inside the house) is 2,300 BTU/hr ( 1/13 x 1,000
sq ft x 30° = 2,307 BTU/hr). In this above example: 7,630 BTUs
escaped outside, and only 2,300 BTUs were stored in the mass of the
house.

Superinsulated home

Superinsulated homes have as their main feature low heat loss. There
are no air plenums as found in the envelope house. There are no
active solar collectors. It's just a plain house from the outside and
the inside. It does not need to be built underground, with a
basement, or on a hillside.
The low heat loss results from unusually high levels of insulation.
When the heat loss from the house is slowed sufficiently, the house
performs very well thermally. However, the house is so well sealed
that it does not get adequate fresh air; it requires one-half day or
up to several days for one air change by infiltration. For this
reason, a fresh air ventilator (air-to-air heat exchanger) is
necessary for stale air to be exhausted and fresh air to be drawn in.
The heat exchanger transfers most of the heat of the outgoing stale
air to the incoming fresh air. McGrath describes five parts to a
superinsulated house: 1) Adequately insulated roof, wall, and floor
sections (termed fixed building sections), 2) the air-to-air heat
exchanger, 3) an arctic entryway, 4) shutters on the windows, and
5) an insulated door. 2 When questioned about the use of window
shutters, McGrath admitted that few superinsulated homes in Fairbanks,
Alaska, use shutters on the windows. The superinsulated design
reduces the heating requirements to such low levels that shutters are
not economically required even in those arctic climates.

The arctic entryway is merely a vestibule or mudroom, outside or
inside, sealed from the rest of the house. It allows people to enter
but prevents cold air from directly entering the house. In this way,
a person enters, closes the door, then goes through another door to
enter the rest of the house. Some analysts have argued that if there
is a good vapor barrier, the cold air will not blow far into the
house. Nonetheless, with a small entry room, the cold air that enters
the house can be limited significantly. This will increase the
comfort of the occupants and will cut down on cold drafts in winter.




Current knowledge suggests that superinsulation should have the
following features:
1. The proper level of continuous insulation in all exterior surfaces
of the building.
2. A continuous vapor barrier.
3. An air-to-air heat exchanger.
4. Proper solar orientation of the windows.
5. An arctic entryway.
6. A nearly continuous radiant barrier (it need not be sealed at
junctions to perform as a radiant barrier).




Part Two
SUPERINSULATION
The Energy-Efficient Solution

Why Superinsulation?

Of all the plans described, superinsulation is the simplest design,
requiring the smallest investment of materials to incorporate energy
saving features; superinsulated buildings can be built in virtually
any location. The design reduces heat loss and serves to recover heat
from all appliances used within the home. The normal amount of
windows is used, while allowing for enough south-facing windows to
contribute to the heating needs of the house. McGrath stated in his
book: "Advocates of superinsulated and passive solar houses have spent
time arguing with each other about which is better, but for my part, I
see no point in it: all superinsulated houses should be passive solar,
and all passive solar homes should be superinsulated." 2

Resolving Vapor Barrier
and Insulation Problems

Vapor barrier problems

A continuous vapor barrier is not present in most conventional
homes. Plumbing connections pierce the vapor barrier. Electrical
wiring and boxes pass through the vapor barrier and are not sealed.
Numerous other breaks are present in the vapor barrier in standard
construction. Even if all of these breaks in the vapor barrier are
sealed, new breaks are made by hanging pictures, mounting towel racks,
and installing recessed wall fixtures.

Insulation problems

Even if all the insulation is properly installed, the wood-framing
members will make up 15 to 25% of the wall area, depending on the
framing techniques utilized. While the insulation is R-11, the wall
studs have less insulating ability (R-5), lowering the final
insulative value of the R-13 wall to about R-10. This stud conduction
problem can be remedied by external insulative sheathing. Since the
inside vapor barrier is less than perfect in standard construction,
moisture accumulation in walls can result from the insulative
sheathing technique unless vapor permeable sheathing is used.



Crosshatch walls

A crosshatch wall helps maintain the vapor barrier integrity by
attaching the vapor barrier to the inside of the framed wall.
Horizontal cross members (2x2s or 2x4s) are attached to the vertical
studs. This reduces heat conduction through the wall and allows space
for electrical wiring without breaking the vapor barrier plane. The
crosshatching method is also known as strapping or cross strapping.19

Double walls

There are several different designs of double walls used to reduce
wall conduction. The methods of making double walls include the party
wall and several possible variations of double walls.
Stud conduction is a main source of heat loss through walls. Another
source of heat loss through walls is conduction through headers used
over doors and windows. A header is a framing member used above
windows and doors that is needed to support the weight of the roof or
floor above. Essentially the entire space within a header is filled
with the framing member itself. This leaves virtually no room for
insulating headers in standard framing. Use of double walls allows
the potential of dramatically reducing heat conduction through headers
as well as conduction through wall studs.




The double wall. Two parallel rows of 2x4 inch framed stud walls
allow for substantially more insulation to be utilized. Conduction of
the top and bottom plates is eliminated, as is stud conduction and
conduction through headers present over doors and windows.








The backward double wall is assembled nearly the same as a standard
platform framed house, except the floor joists should be cantilevered
to the position of the projected outside wall. The vapor barrier is
mounted between the sheathing and studs of the inner wall. Earlier
versions placed the vapor barrier on the outside of the inner wall.
However, Canadian research suggests that the vapor barrier could be
damaged more readily by wind loading. Also, exterior mounting of the
vapor barrier prolongs the exposure to UV light during construction
and increases the chance it will get damaged before the exterior wall
is completed. If the vapor barrier is mounted exterior to the
sheathing, it must be well fastened down (e.g., sealed and secured in
place by wood strips) to prevent it from detaching under windy
conditions.
The backward double wall allows space within the inner wall for the
electrical wiring, piping, recessed fixtures, and relative safety of
the vapor barrier from most internal home modifications. The
insulation is placed exterior to the inside wall. This allows the
vapor barrier to remain intact for the life of the house, since it is
well protected by the thickness of the inside wall. The backward
double wall can be made so that the inside wall, the outside wall, or
both walls are load-bearing.
The backward double wall has the best features to protect the vapor
barrier, reduce stud conduction, and provide as much space as needed
for the insulation to be used. The inside wall cavity does not
require insulation because the wall cavity external to it can hold all
the needed insulation. If 12 inches of insulation are used in the
wall (R-40 wall), the wall will have a total thickness of 16 inches
plus the external siding. The internal 3½ inches is taking up space
but not contributing either to inside space or to insulation.




Temperature gradients and the backward double wall

Wall temperatures drop progressively from the inside wall to the
outside of the building. Depending on the relative humidity of the
inside air, moisture could condense before reaching the vapor
barrier. With the air-to-air heat exchanger running continuously at
an adequate rate, sufficient moisture will be removed from the inside
of the house to drop the relative humidity to a safe level.
The inside wall can be used for additional insulation and not cause
condensation problems, as described by the superinsulators of Alaska
and Saskatchewan, Canada. At least two-thirds of the insulation
should be external to the vapor barrier (2:1 ratio) for moderately
cold climates that never get below 0° F. For colder climates it is
advisable to have a 3:1 or 4:1 ratio of outside to inside
insulation. With 12 inches of insulation external to the vapor
barrier and 3½ inches of insulation (all fiberglass) inside the vapor
barrier (3.4 : 1 ratio), there should be no condensation inside the
wall even if the outside temperature drops to -60° F (if less than
35% indoor relative humidity is maintained). The additional
insulation would increase the insulation properties of the R-40 wall
to R-50.









If moisture is not being removed from the house to keep it below the
proper relative humidity for the coldest conditions expected, there is
significant danger in using insulation on the warm side of the vapor
barrier. Condensation in the inner wall could rot the studs, causing
serious structural damage to the home.
For additional details on design and construction of superinsulated
wall types, also consult The Superinsulated Home Book, by Nisson and
Dutt. 41


Heat Loss Calculations

Standard guidelines for determining the size of a heating system
needed in a home do not apply to energy efficient houses. The heat
loss from energy efficient houses is so slight that conventional
systems overwhelm the heating needs. It is necessary to make some
preliminary calculations to determine the heating output needed to
keep the house comfortable in all conditions. Heat loss factors from
various surfaces as well as the energy needed to heat the ventilation
air are important considerations.

Heat loss / gain formulas:

Heat loss (BTU/hr) = U (heat transmission) x Area (sq ft) x ∆T (°F)
or
Heat loss (BTU/hr) = 1/R for the surface x Area (sq ft) x ∆T (°F)

Sample calculation I. For an uninsulated 2x4 inch frame wall (R-4),
with 100 square feet of wall area and an inside to outside temperature
difference of 70° (0° F outside and 70° inside = ∆T), the heat loss
can be calculated:

Heat loss = 1/4 x 100 sq ft x 70°
Heat loss = 1750 BTU/hr

Sample calculation II. For a standard 2x4 inch frame wall with
insulation (R-13), with 100 square feet of wall area, ∆T = 70°, the
heat loss can be calculated:

Heat loss = 1/13 x 100 sq ft x 70°
Heat loss = 538 BTU/hr

Sample calculation III. For a superinsulated wall, e.g., 12 inches of
insulation (R-40 for the wall), with 100 square feet of wall area, ∆T
= 70°, the heat loss can be calculated:

Heat loss = 1/40 x 100 sq ft x 70°
Heat loss = 175 BTU/hr

When the total heat loss of a building drops to a sufficiently low
level, the heat gained by the "living process" inside the home starts
to make up much of the remaining heating demands. Heat from the
living process, also termed internal gains, comes from heat given off
by people, lights, and appliances. These internal gains can provide
1500 to 3000 BTUs per hour to the heat requirements of a residential
home. Each kilowatt-hour (KWH) of electricity used in the home gives
off 3,410 BTUs.


Each person gives off heat, depending on the person's size and energy
expenditure (100 to 600 BTU/hr).2 The actual gains will vary with the
number of occupants, the energy usage of the occupants, and the actual
home appliances. Once the heat loss is very low, the internal gains
of the home will make up a significant percentage of the home heating
needs.

Heat loss calculations for five sample houses (winter)

The specifications of a house to be used for heat loss calculations
are: 28 feet by 44 feet in floor area, single story over a crawl
space, 8 foot ceiling, having 80 square feet of south-facing glass, 24
square feet of east-facing glass, and 40 square feet of north-facing
glass. There are two doors 20 square feet each. The nighttime
average temperature is calculated at -10° F (for 12 hours), and the
daytime average is +20° F (for 12 hours). The inside temperature is
kept at 70° F. Location is 40° north latitude (southern
Pennsylvania), with 50% sunshine during the month of January.
Calculations include internal gains of 1,500 BTU/hr.

Example 1. An underinsulated house (minimal ceiling insulation), with
spontaneous infiltration of 1.0 air change per hour and single-pane
windows.
Example 2. A normally insulated house with a spontaneous infiltration
rate of 0.5 air changes per hour and double-pane windows.
Example 3. A superinsulated house with ventilation controlled at 0.5
air changes per hour and triple-pane windows.
Example 4. A superinsulated house with an air-to-air heat exchanger
(75% efficient) providing ventilation of 0.5 air changes per hour, and
triple-pane windows.
Example 5. This house is identical to example 4, except that the owner
added on a sunspace having 100 square feet of south-facing standard
double-pane glass. The sunspace is separated from the house and
provides the home 50% of received solar heat by way of a
thermostatically activated fan.
Notes on sunspaces: See the solar gain tables, overhang tables, and
section on window orientation and energy efficiency to design the
optimum thermal performance of sunspaces. A sunspace with south-
facing windows can serve to collect solar heat for the home. However,
the large window area results in substantial heat loss in winter after
sunset; to prevent heat loss from the home, the sunspace should be
thermally separated from the house. A sunspace used for supplemental
heating should have mainly vertical south-facing windows and little
thermal mass (such as wooden walls and floors) to allow the
thermostatic fan to duct excess heat to the house. A sunspace used as
a greenhouse will need more thermal mass (concrete or brick walls and
floors) so the heat can be absorbed and retained in the greenhouse,
although not providing much additional heat for the house.

Source Example
1 2 3 4 5

Wall R-value 4 13 40 40 40
Ceiling R-value 6 19 50 50 50
Floor R-value 4 13 40 40 40
Window R-value 0.89 1.84 2.79 2.79 2.79
Door R-value 4 8 15 15 15
Window loss (BTU/°F/hr) 162 78 52 52 52
Walls + ceiling
+ floor loss (BTU/°F/hr) 755 234 80 80 80
Door loss (BTU/°F/hr) 10 5 3 3 3
Heat for ventilation
air (BTU/°F/hr) 177 88 88 22 22
Net heat loss
(BTU/°F/hr) 1,104 405 223 157 157
Heat loss/hr
@ -10°F (80° ∆T) 88,320 32,400 17,840 12,560 12,560
Heat lost/24 hrs (12h
@-10°; 12h @+20°) 1,722,240 631,800 347,880 244,920 244,920
Heat gain (solar) 67,164 57,762 49,674 49,674 81,511
Internal gains 36,000 36,000 36,000 36,000 36,000
Net heat
needed/day 1,619,076 538,038 262,206 159,246 127,409

Hours/day an 80,000 BTU furnace must run to maintain inside
temperatures of the
sample homes: 20.23 hrs 6.72 hrs 3.27 hrs 1.99 hrs 1.59 hrs

Calculations for heating ventilation air. Air volume per hour (cubic
feet/hr) x 0.018 BTU/cu ft/°F/hr (specific heat and density factor) =
BTU/hr needed to heat the air. If a heat exchanger is used, multiply
the result of this calculation by 0.25 (75% of the heat is recovered,
25% of the heat must be added). 28' x 44' x 8' (ceiling height) =
9,856 cubic feet, which is one air change for this sized house. 9,856
cu ft x 0.5 (when 0.5 air changes is the infiltration or ventilation
rate) = 4,928 cu ft/hr (or 82 cubic feet per minute as a ventilation
rate).
Wall calculations. 1152 sq ft of walls, less 40 sq ft of doors and
144 sq ft of windows, gives 968 sq ft x 1/R = heat loss/°F/hr for
walls.
Ceiling calculations. 1232 sq ft x 1/R = heat loss/°F/hr for ceilings
Floor calculations. 1232 sq ft x 1/R = heat loss/°F/hr for floors
Door calculations. 40 sq ft x 1/R = heat loss/°F/hr for doors
Window loss calculations. 144 sq ft x 1/R = heat loss for windows
Window gain calculations. Solar gain tables in part four of this book
are calculated for double-pane glass. Increase the calculated gains
for single-pane windows (in example 1, divide the gain for each window
by 0.86 to get the single-pane values). Reduce the calculated gains
for triple-pane windows (multiply the values by 0.86).
South window area (80 sq ft) x 0.90 (framing) x 0.50 (proportion of
sunny days) x 1415 BTU/sq ft/day January heat gain.

East window area (24 sq ft) x 0.90 (framing) x 0.50 (percent sunny) x
445 BTU/sq ft/day January heat gain.
North window area (40 sq ft) x 0.90 (framing) x 0.50 (percent sunny)
x 112 BTU/sq ft/day January heat gain.
Sunspace area (100 sq ft) x 0.90 (framing) X 0.50 (proportion of
sunny days) x 0.5 (proportion vented to home) x 1415 BTU/sq ft/day
January heat gain.



Summary of winter calculations

Uninsulated and underinsulated homes lose a substantial amount of
heat during cold winter days and nights. Solar gains and internal
gains make up only 6% of the heating needs.
Conventionally insulated homes require only 33% of the heat of the
underinsulated homes. The internal and solar gains now make up about
15% of the heating needs.
A superinsulated house would lose only 14% of the heat of an
underinsulated home. The internal and solar gains make up 35% of the
heating needs. The result is that the superinsulated home needs only
10% of the furnace heat when compared to an underinsulated home. The
superinsulated home needs only 30% of the furnace heat compared to
homes with conventional amounts of insulation.
The addition of a sunspace to the superinsulated home further reduces
the heating demands. The 127,400 BTU deficiency per day could be
supplied by occasional use of a fireplace, heat pump, or small
furnace.




Summer heat gain calculations

The same home specifications as for winter are used in calculating
the summer heat gain. For comparison, we will vary the amount of east/
west windows with the north/south windows of other examples. The
nighttime average temperature is calculated at 75° F (for 12 hours)
and the daytime average is 100° F (for 12 hours). The attic
temperatures, however rise higher, averaging 120° (for 12 hours). The
inside temperature is maintained at 75° F. Location is 40° north
latitude, with 85% sunshine during the month of July. Calculations
include internal gains of 1,500 BTU/hr.

Example 6. An underinsulated house (minimal ceiling insulation), with
spontaneous infiltration of 1.0 air change per hour. (Windows: 80 sq
ft South, 24 sq ft East, 40 sq ft North; all windows are single-pane.)
Example 7. A normally insulated house with a spontaneous infiltration
rate of 0.5 air changes per hour. (Windows: 80 sq ft South, 24 sq ft
East,40 sq ft North; all windows are double-pane.)
Example 8. A normally insulated house with window orientation
different from example 7. (Windows: 80 sq ft West, 24 sq ft North,
40 sq ft East. )
Example 9. A superinsulated house with an air-to-air heat exchanger
(75% efficient) providing ventilation of 0.5 air changes per hour.
(Windows have same orientation as example 8, above): 80 sq ft West, 24
sq ft North, 40 sq ft East; all windows are triple-pane.
Example 10. A superinsulated house with an air-to-air heat exchanger
(75% efficient) providing ventilation of 0.5 air changes per hour.
(Windows have same orientation as example 7, above): 80 sq ft South,
24 sq ft East, 40 sq ft North. all windows are triple-pane.)


Source Example
6 7 8 9 10

Wall R-value 4 13 13 40 40
Ceiling R-value 6 19 19 50 50
Floor R-value 4 13 13 40 40
Window R-value 0.89 1.84 1.84 2.79 2.79
Door R-value 4 8 8 15 15
Window gain
(BTU/°F/hr) 162 78 78 52 52
Walls + floor heat gain 550 170 170 55 55
Door gain 10 5 5 3 3
Cooling of ventilation
air (BTU/°F/hr) 177 88 88 22 22
Net heat gained
(BTU/°F/hr), less ceiling 899 341 341 132 132
Heat gain/hr, less ceiling
@ 100°F (25° ∆T) 22,475 8,525 8,525 3,300 3,300
Ceiling gain (BTU/°F/hr) 205 65 65 25 25
Ceiling gain (@ 120°)
(45° ∆T) BTU/hr 9,225 2,925 2,925 1,125 1,125
Heat gain/24 hrs (12h
@100°;12h @75°) 380,400 137,400 137,400 53,100 53,100
Heat gain (solar) 73,474 63,188 97,289 83,668 54,340
Internal gains 36,000 36,000 36,000 36,000 36,000
Net cooling
needed/day (BTU/day) 489,874 236,588 270,689 172,768 143,440

Hours/day a 30,000 BTU air conditioner must run to cool the house
16.33 hrs 7.88 hrs 9.02 hrs 5.75 hrs 4.78hrs

Window gain calculations. Increase the calculated gains for single-
pane windows. (In example 7, divide the double-pane values for each
window by 0.86 to get the single-pane values.) Reduce the calculated
gains for triple-pane windows (multiply the double-pane values by
0.86).
South window area x 0.90 (framing) x 0.85 (proportion of sunny days)
x 550 BTU/sq ft/day July heat gain.
East/west window area x 0.90 (framing) x 0.85 (percent sunny) x 985
BTU/sq ft/day July heat gain.
North window area x 0.90 (framing) x 0.85 (proportion of sunny days)
x 374 BTU/sq ft/day July heat gain.

Sunspace area. Although the earlier mentioned sunspace (example 5)
has gains in summer, the windows are opened for excess heat to go
outside. The thermostatic fan is turned off for the summer. The
sunspace is thermally separated from the house in summer, thus does
not increase the cooling demand.




Summary of summer calculations

Uninsulated and underinsulated homes gain a significant amount of
heat during hot summer days. Conventionally insulated homes require
about 48% of the cooling of underinsulated homes. Window orientation
is significant in summer also. A greater proportion of east and west
windows can easily make a home have 50% more summer solar gains than
when east/west windows are minimized. This increases the cooling load
and makes the home more uncomfortable, causing a 20% increased cooling
load in the superinsulated house. (Compare examples 9 and 10.)
Window factors being equal, superinsulation has 29% of the summer
cooling bills of an underinsulated house. The superinsulated house
has 61% of the cooling bills of a conventionally insulated house.
In summer, solar and internal gains add to the cooling load; in
winter, the solar and internal gains decrease the heating load.
Therefore, energy savings in summer are not so dramatic for
superinsulation as in cold winters, although increased insulation
levels will reduce cooling costs significantly.
Additional factors to be considered:
1. If south windows are provided a proper overhang, direct summer sun
is blocked, while the winter sun can still obtain full exposure. The
actual solar gains in summer would be less than half of the calculated
values for the south windows if a proper overhang is provided.
2. When the outside temperature is 100° F, the attic temperatures can
potentially be much higher than 120°, making greater depth of attic
insulation even more important in summer. A radiant barrier in the
attic can drop ceiling heat gain to far lower levels.
3. The air is often cooler near the floor than the ceiling. This
changes the heat loss/gain data, but was not calculated here.

Shape of the Building and Heat Loss and Gain

Since heat loss is related to surface area, the shape of the building
is an important factor. The more surface area, the faster the heat
loss. The smaller the surface area, the slower the heat loss, when
all other factors (such as insulation levels) are kept constant.
A sphere has the least surface area for a given volume. Using normal
building shapes, two-story buildings and square shapes lose less heat
than single-story buildings and long rectangular shapes when exterior
surfaces are equally insulated.

Example A. A single-story ranch house of 2,000 square feet living
area has 5,440 square feet of outer surface area. Assume 50 feet by
40 feet house dimensions, with 8 foot ceilings. (40 ft x 8 ft x 2
walls) + (50 ft x 8 ft x 2 walls) + 2,000 sq ft ceiling + 2,000 sq ft
floor = 5,440 sq ft surface area.
Example B. A two-story house with 1,000 square feet living area per
floor has 4,210 square feet of outer surface area. Assume 40 feet x
25 feet house dimensions with 17 feet combined height of the two walls
plus the floor between. (40 ft x 17 ft x 2 walls) + (25 ft x 17 ft x
2 walls) + 1,000 sq ft ceiling and 1,000 sq ft floor = 4,210 sq ft
of surface area. If the house shape is totally square for each floor,
the surface area is 4,150 square feet.
A two-floor design, still keeping the same total living area, has an
outer surface area of only 77.4% of its earlier amount. This means
heat loss from the outer surface is also reduced if insulation levels
in all exterior surfaces are kept the same. Changing from a one-story
to a two-story design can save space-heating energy.
Solar gain is related to the window orientation and size. The long
sides of the house facing north and south allow sufficient south-
facing windows. The optimum building shape is north and south sides
of the building 1.5 times longer than the east and west sides of the
building,6 e.g., if the east/west sides are 28 feet long, the north/
south sides of the building should be 42 feet long. This ratio
provides a suitable amount of space for placement of south windows,
with only a slight increase in building surface area.
The 2,000 square foot building in Example "A," would have 5,431
square feet of outer surface area for a square shape (44.7 x 44.7
ft). If the shape is changed to 37 ft x 55 ft (using the 1.5 ratio),
the outer surface area would be 5,472 square feet, only a slight
increase in surface area. The 1.5 ratio results in the area of the
south wall being 50% greater than the east or west wall, allowing for
placement of the necessary south-facing windows.
The two story 2,000 square feet building in example "B": a 26 ft x
39 ft floor size results in 4,210 square feet outer surface area. The
1.5 ratio results in a slight increase of surface area over a square
floor area (4,150 sq ft).
While decreasing external surface area of a building offers the
potential for decreased energy consumption, it does not guarantee it.
The actual insulation level in each section of a building is also a
very significant factor in the final energy used for space heating.


Thermal Mass and the Drop of Temperature

The total effect of insulation in a building determines the rate of
heat loss (BTU/hr). The speed by which temperature of the building
drops is determined by its heat-holding capability. This heat-holding
capability is referred to as the thermal mass of the building.
All materials hold a certain amount of heat depending on the specific
heat of the material and its density.

Properties of heat storage materials

Material Specific heat Density Heat capacity (BTU/cu ft/°F)
(BTU/lb/°F) (lb/cu ft) No voids 30% voids

Water 1.00 62 62 43
Scrap iron 0.12 490 59 41
Scrap aluminum 0.23 170 39 27
Concrete 0.23 140 32 22
Stone 0.21 170 36 25
Brick 0.20 140 28 20

Data obtained from New Energy Technology: Some Facts and Figures,
edited by Hottel and Howard. Published by MIT Press.

When basement walls are insulated exteriorly by foam boards, the
thermal mass of the concrete walls is within the building, serving to
store heat. The brick of a fireplace built within the insulated
enclosure is thermal mass within the building. However, it is common
that brick of fireplaces is continuous with the inside and outside,
resulting in much heat loss from the building. The uninsulated brick
does not function as thermal mass, since heat cannot be stored unless
insulation retains the thermal energy. An exterior brick façade
cannot function as thermal storage for the building. A brick wall as
an interior partition provides thermal storage.
Everything that is inside the building stores heat, all interior
walls, furniture, and appliances. A standard house can have 10,000
BTU storage capability without any planning for heat storage; for each
10,000 BTUs of heat lost, such a house loses 1° F. The uninsulated
house in example 1 (in winter), loses 88,320 BTU/hr for an outside
temperature of -10° F. The inside temperature would drop about 9° in
the first hour if no heat were added. The standard insulated house
loses 32,400 BTU/hr (example 2), and the temperature would drop about
3° in the first hour. The superinsulated house with the heat
exchanger loses 12,560 BTU/hr (example 4) and drops just over 1° F in
the first hour.


If special measures are taken to add thermal mass, the temperature
drop would be much slower. One way of adding thermal mass is by
having a small room in the basement filled with sealed water jugs.
One thousand gallons of water stored in the room would add about 8,600
BTU storage capability. Air circulating through the water storage
room would give off heat as the house needed it, slowing down the heat
loss of the house. The temperature of the superinsulated house
(12,560 BTU/hr loss, example 4) would drop about 7° over a 12-hour
period with the higher level of thermal mass. (12,560 BTU/hr x 12
hours, less 18,000 BTU internal gains in 12 hours gives 132,720 BTUs
lost in 12 hours [at -10°F]. Since there is now an 18,600 BTU storage
capability of the house, about 7° would be lost in the 12 hours
[132,720 BTU/hr ÷ 18,600 BTU/°F = 7.14°].) An overnight power/heat
failure would not be a crisis in a superinsulated house. However, an
uninsulated house would be below freezing by the morning. The true
heat loss would be fractionally smaller, since as the house loses
heat, the ∆T decreases, thereby slowing the heat loss slightly.

Heating System

Sizing it to the needs of your house

A forced air ventilation system is an advantage to have in a home
receiving plentiful solar gain. The ventilation system can be turned
to the "fan" setting during the day, allowing for the passively heated
air to be distributed so that the heat is stored evenly throughout the
mass of the house.6, 19 Alternatively, duct boosters properly placed
in the duct system could circulate the air at a lower electrical cost.
There is a large difference between the heat needs of the uninsulated
house (88,320 BTU/hr in example 1) and the superinsulated house
(12,560 BTU/hr in example 4). Conventional gas or oil-fired heating
systems are geared to provide enough heat for poorly insulated
houses. Such furnaces are often greater than 70,000 BTU/hr capacity.
Smaller sized furnaces are now available in the 20,000 to 40,000 BTU/
hr range, which would be suitable for superinsulated houses. (See
furnace manufacturer listings.)
Wood stoves and fireplace inserts also provide heat, often exceeding
the needs of well-insulated houses. Use of a wood stove requires a
brief time of combustion to raise the temperature of the home and then
a cool-down period until it is necessary to re-light the stove to
reheat the home. Wood stoves and fireplaces tend to have excessive
emissions; their use is restricted by legislation in some areas. The
emissions are reduced, dangerous creosote deposits in the chimney are
reduced by 90%, and additional heat is produced by use of a catalytic
element in the exhaust gas pathway. Catalytic units are available
with some wood stoves and fireplace inserts.
Electrical resistance heaters can supply a wide range of heat demands
and are quite affordable. Electrical resistance heat has been termed
100% efficient, all electricity being converted to heat.
Unfortunately, electrical heat is more expensive per BTU. Electricity
is often derived from burning of fossil fuels, which could directly
heat the home. As fuels are burned and electricity is produced and
delivered, about one-third of the energy from the fuel actually
reaches the home. Burning natural gas to run a generator to heat a
home with the electricity so generated requires up to three times as
much gas burned as gas burned in the house furnace. 2

Another way of using electricity to generate heat is use of a heat
pump. A conventional heat pump moves excess heat from the home in
summer and releases the heat outdoors. When the mode is reversed, the
unit extracts heat from cold outside air and brings the heat indoors
for winter use. Efficiency of the heat pump is highest when inside
and outside temperatures are fairly similar. Conventional heat pumps
can attain coefficients of performance (COP) of up to 5 or 6. For
every kilowatt put into powering the compressor motor, 5 or 6
kilowatts of heat energy are obtained. 2 Since a superinsulated
house usually does not need heat until the outside temperature is near
freezing, the coefficients of performance (COP) may not be as
favorable. Once the COP drops down to 1.0, efficiency is the same as
using electrical resistance heating; when outside temperatures drop to
+5° F, the COP is down to about 1.0. As long as the heat pump is
operating at an efficiency greater than 3, it is operating at the same
efficiency as if fuel producing the electricity were burned in the
home.
Considering the rate of heat loss from conventional homes, it would
take a high capacity heat pump to supply the heating needs of the
house when outside temperatures drop to +20°F. Since heat pump
efficiency is related to outdoor temperatures and winter causes high
heat demands, back up electrical resistance heat is typically provided
for heat pump operation. When the heat pump cannot supply the heat
demands, or if the efficiency drops too low, the back-up heat will
activate. Some heat pumps are designed to operate with a fuel (other
than electricity) for back-up heat; when the efficiency of the heat
pump drops to a certain level, the back-up fuel system will engage.
Another heating option is an oversized water heater used to supply
additional warmth for space heating, with heated water circulating
through coils into the forced air ventilation system of the house or
to a separate radiator unit. Water heater supplied space heating is
suitable only when powered by fuels less expensive than electricity.

Geo-thermal heat pumps

Another approach to heat pumps is a geo-thermal heat pump. The
outside part of the pump is a closed loop of water running underground
through polyethylene or polybutylene piping. From the ground the
water extracts heat in winter and coolness in summer. (The ground is
warmer than the air in winter and cooler than the air in summer.) For
cooling the geo-thermal heat pump can attain an EER efficiency rating
up to 15; for heating, it can have a COP as high as 3.98. 20 A geo-
thermal pump can also provide hot water instead of using a
conventional water heater. It is best to plan for a geo-thermal heat
pump in advance of construction. About 400 feet of 1.5-inch
polyethylene piping must be buried 4 to 6 feet in the ground to
provide heat exchange for each 12,000 BTU/hr ("one-ton") capacity. If
the heat exchange pipes are within several feet of other heat exchange
pipes, more pipe length will be needed (up to 670 feet per ton
capacity). With the low energy demands of a superinsulated house, a
one-ton capacity could suffice.




Geo-thermal heat pumps: Earth loop configurations
Adapted from: Manual of Acceptable Practices for Installation of
Residential
Earth-Coupled Heat Pump Systems by W.S. Fleming and Associates,
Inc.



For normally insulated homes, the usual methods are to:
1. Excavate an area of the yard to bury the piping.
2. Drill a deep well and insert a heat exchange tube.
3. Drill multiple shallow wells with exchange tubes, or
4. Bury the heat exchange pipes in the septic drainage field, if on-
site sewage disposal is used.

Superinsulated homes will typically require only one-third the
capacity of conventionally insulated homes. Alternatively, ground
water may be used as the heat or cooling source for a geo-thermal pump
by drilling wells, although it requires large volumes of water and may
go against local or federal codes to discharge water (or heated water,
in areas where thermal pollution is an ecological consideration).

For a superinsulated house, a geo-thermal heat pump makes more sense
than a standard air-source heat pump. A superinsulated house will
rarely need heat until the outside temperatures drop near freezing.
When the outside temperatures drop near freezing, a standard heat pump
has fairly low efficiency. Geo-thermal heat pumps rely on ground
temperatures for heat exchange; ground temperatures are typically much
warmer than outside air temperatures during the coldest times of
winter. A properly-sized geo-thermal heat pump will maintain good
efficiency throughout winter despite low outside air temperatures.
The addresses of geo-thermal heat pump manufacturers are listed after
the references.

Heating systems: Is too big always too big?

Texts on energy-efficient housing usually recommend heating systems
sized within 10% of the house heating demands. 6 A 20% oversized
system tends to lose heating efficiency, thereby wasting part of the
energy. A large amount of energy is wasted when the burner is fired
and turned off.19 However, a system sized just for the heat demands
of the house does not allow rapid re-heating after the heat control
was turned down during periods of absence. When the occupants take
extended vacations in winter, they turn down the heat to save energy
(and costs). The heater keeps the house at the low level of 55°F
during their absence, requiring a very long time to reheat on
return. Not only must the air temperature be raised, but the
temperature of the thermal mass of the house must also be raised. In
an example of a house with a thermal mass of 10,000 BTU/°F, the
occupants want to raise the house temperature back to 73°F. To raise
the temperature 18° requires 180,000 BTUs of heat, even when outside
losses are not computed (18° F x 10,000 BTU/°F thermal mass =
180,000 BTU). If the energy efficient house has a 20,000-BTU heat
pump, and the outside losses are at 8,000 BTU/hr, it will take 15
hours for the home to reheat before the heater will shut off. (20,000
BTU/hr heat output minus 8,000 BTU/hr heat loss, leaves 12,000 BTU/hr
to heat the house back to normal temperatures. 12,000 BTU/hr x 15
hours = 180,000 BTU.) With a small-capacity furnace or heat pump, the
occupants would be inclined to leave the heat at a livable temperature
during their absence to reduce the reheat time. However, an
“extravagant” 40,000 BTU furnace would allow the house to reach its
temperature in less than 6 hours. (40,000 BTU/hr less 8,000 BTU/hr
heat loss, leaves 32,000 BTU/hr to heat the house back up. 32,000 BTU/
hr x 5.7 hrs = 182,400 BTU.) If the home can be reheated in a
relatively short time, the occupants would be more willing to have the
thermostat set low or off at night or set low during prolonged
absences, since the house could be warmed quickly when necessary. The
theoretical extravagance or wasted energy of an oversized heater is
not valid in all cases. Depending on the lifestyle of the occupants,
it may be preferable to keep the heating system oversized when
prolonged periods of shutoff are anticipated.


Cooling Tubes for Summer Cooling?

Envelope homes utilize underground cooling tubes in summer. Air is
drawn through a 50-to-70-foot- long aluminum culvert pipe 2 feet in
diameter, buried 6 to 7 feet underground.18 Outside air is drawn into
the cooling tube, travels 50 to 70 feet underground, and enters the
house. Heated air is exhausted passively from vents at the top of the
house. The cooling tube allows enough time and distance to cool the
air nearly to ground temperature. This provides nearly free cooling
for the house. The use of such cooling tubes (earth tubes) could
reduce significantly the cooling demand of a well-insulated home in
summer.
Deep in the ground, the temperature stays fairly mild in winter (45°F
when the air is 0°F). The earth tube would partially preheat
ventilation air in winter, reducing the energy needed to warm the
ventilation air. The tubes would also reduce frosting-up tendencies
of the air-to-air heat exchanger when outside temperatures drop very
low.
See the next page, “Potential problems with cooling tubes” for likely
drawbacks on their use.

Cooling tube (earth tube)


As an example, a superinsulated home in Minnesota did precisely that.
21 Fresh air is drawn through a 120-foot-long pipe 12 inches in
diameter buried 8 to 12 feet underground. Outside air brought through
this pipe is warmed by the ground to 45° in winter and cooled to 55°
in summer. Air from the vent is used to supply air to the heat
exchanger. Then the heat exchanger raises the temperature of intake
air nearly to room temperature. Since the air is warmed to 45° in
winter, the whole problem of heat exchanger frost-up is eliminated.
As winter temperatures in Minnesota are frequently below 0°F,
preheating of the air is quite significant. Low-temperature intake
air from the earth tube reduces the need of additional cooling for
most of the summer. When cooling is needed in the summer, the air
from the intake pipe (55° F) is directly routed into the home,
bypassing the heat exchanger core. In this way, cool air enters the
house without having to use air conditioning.
Cooling capability of cooling tubes. In order to eliminate the need
for air conditioning, it is necessary for the cooling tube to provide
cool incoming air to replace the hotter exhausted air. In example 10
of the summer heat gain data, the home gains 144,000 BTUs over a 24-
hour period. This averages 6,000 BTU/hr or 100 BTU/minute. If the
cooling tube were able to supply 55° F incoming air, and the hottest
air exhausted were 80° F, about 225 cfm airflow would remove
sufficient heat to keep the house cool. (225 cfm x 25° ∆T x 0.018
[specific heat and density factor] = 101 BTU/minute.) The Minnesota
superinsulated house referenced kept a steady intake air temperature
of 55° F during the summer. 21

Cooling tube (earth tube)
For ventilation, a 12-inch-diameter metal pipe, 40 to 120 feet long,
buried as deep as the foundation will allow.


A separate trench can be dug for the cooling tube, or the foundation
trench can be used to hold the cooling tube for new construction. A
house with dimensions of 44 feet by 28 feet has an outside perimeter
of 144 feet, more than enough length for a 120-foot air intake pipe
placed at the bottom of the foundation trench before back-filling.
The length of cooling tube needed to provide temperature stability
should be considered. A geo-thermal heat pump used in moist soil in
England provided 46.8 BTU/hr per linear foot of pipe.22 The copper
pipe used was one inch in diameter, which would have a surface area of
38 square inches per linear foot. For each square-inch surface area
buried deep enough underground, the amount of heat that was given off/
absorbed by the ground was 1.24 BTU/hr (46.8 BTU/sq in/hr ÷ 37.7 sq in
= 1.24 BTU/hr). A 12-inch diameter pipe of 120-foot length has 54,280
square inches surface area, which could theoretically give off/absorb
up to 67,315 BTU/hr. To cool air at the rate of 225 cfm from an
outside air temperature of 100°F to 55°F would take only 10,935 BTU/
hr (225 cfm x 0.018 x 45° ∆T x 60 minutes/hr = 10,935 BTU/hr).
Perhaps the cooling tube could be significantly shorter to provide
adequate cooling of the air in the example cited. Dry ground does not
have the ability to transfer heat as rapidly as wet ground; thus drier
ground requires a greater surface area of contact. Considering heat
load of the building, ground temperature at the depth used, and ground
moisture, about 40 to 120 feet of 12-inch-diameter pipe is sufficient
length to cool an energy efficient home. As a minimum depth, the
earth tube should be buried below the frost line. Ground temperatures
tend to be most stable more than 7 feet below the surface. At 20 feet
below the surface of the earth, the temperatures stay essentially
constant year-round.

Potential problems with cooling tubes

Since the cooling tube travels underground, the possibility exists
that joints or seams in the cooling tube could be a source of radon
infiltration by drawing radon in from the soil. This means that a
home with a well-sealed basement, having essentially no radon
infiltration, could now have a new source of radon infiltration
through sealed or unsealed joints in the cooling tube.

Use of a cooling tube, while decreasing air conditioning demands or
decreasing costs of heating ventilation air in winter, could increase
home air quality problems due to radon contamination.41 If radon
contamination is not enough worry, the excessive humidity in cooling
tubes in summer can result in mold and fungus growth.42 As the summer
drags on, the continual flow of hot outside air through the cooling
tube eventually raises the temperature of the surrounding soil. As
the season continues, the cooling tube, therefore, loses its
effectiveness.
All of these factors perhaps make the use of "cooling tubes" of
questionable value. These underground air conduits were considered an
essential part of envelope homes. This is just one more factor
showing that envelope homes have too many potential flaws. Envelope
homes use cooling tubes to supply fresh, cool air in summer. In
actuality the performance of cooling tubes degrades with longer
summers, and cooling tubes have additional risks of air contamination
through radon infiltration and from mold and fungus growth.
Although a cooling tube might keep a house cool, it would not remove
significant humidity. For example, with the outside temperature 90°F
and 50% relative humidity, the cooling tube cools the air to 60°F.
The 60° air coming in from the cooling tube will have essentially the
same total amount of moisture, now nearly 100% relative humidity. It
is therefore necessary to dehumidify cooling tube air that is
introduced into the home during summer. A dehumidifier or air
conditioner can effectively remove excess humidity.
It is possible to get the benefits of earth-assisted cooling (and
dehumidification) in summer without the associated risks of radon or
fungus growth. This method is described several pages earlier in the
section on "geo-thermal heat pumps." By this method, the stable earth
temperatures are used to provide summer cooling and winter heating.
In the summer cooling mode, the geo-thermal heat pump dumps heat into
the soil. In winter, excess heat is extracted from the soil. With
geo-thermal heat pumps, there is still decreased effectiveness late in
the summer season. However, after the end of the summer, this excess
heat in the soil might slightly increase the effectiveness of the
system early in winter.

Indoor humidity control in summer

Dehumidification is important for effective cooling. A dehumidifier
or an air conditioner can remove excess humidity in summer. A
dehumidifier is similar to a small air-conditioning unit in having a
heat pump compressor and cooling coils to condense humidity. However,
the heat pump of the dehumidifier transfers the heat into coils just
behind the cooling coils. As air passes through a dehumidifier, air
is drawn in by the fan, passes over the cooling coils (becoming both
cooled and dehumidified), passes over the heat coils (becoming
reheated), and exits the dehumidifier with less moisture but slightly
warmer than it entered. The increased heat of the air is due to the
operating heat given off by the unit.
An air conditioner has the basic parts of the dehumidifier, except
that the cooling coils are inside the house and the heating coils are
outside. The air conditioner requires an inside and outside fan
unit. However, fan power is a relatively small part of the total
power consumption of the unit. For nearly the same energy cost (air
conditioner versus dehumidifier), the air conditioner provides the
added advantage of cooling. If one needs cooling along with
dehumidifying, it makes more sense to use a small air conditioner
rather than a dehumidifier.

How Much Insulation Is Actually Needed?

McGrath explains a formula for determining the amount of insulation
to be used in walls, ceilings, and floors in a given climate.

R-value needed = Heating degree-days x 0.004

McGrath termed this formula the Roggasch variable R value rule, named
for the person who empirically determined the formula. It postulates
that a building can afford to lose 6,000 BTU from each square foot of
its exterior surface in a year. The heating degree-days value (DD)
for the year is used to arrive at the insulation level needed. (DD ÷
R-value x 24 hours = 6,000 BTU/year. Rearranging this formula, we get
R = DD x 24 ÷ 6,000. Therefore R-value = DD x 0.004.)
Superinsulation theorists in Alaska feel that all external surfaces,
walls, ceilings, and floors (fixed building sections) have essentially
the same outside temperature and should be equally insulated. 2
Using this formula, the arctic areas of Alaska would need about R-60
in the fixed building sections.

R = 14,500 degree-days (Fairbanks, Alaska) x 0.004 = R-58

Similar calculations can be made for other climates. Duluth,
Minnesota (10,000 degree-days), needs R-40 fixed building sections.
Helena, Montana (8,129 degree-days), needs R-32. Denver, Colorado
(6,300 degree-days), needs R-25. Under this formula, Savannah,
Georgia (1,850 degree-days), needs only R-7. Unfortunately, the
formula does not take cooling demands into consideration. Therefore,
heating degree-days are quite inaccurate in climates where air
conditioning is the main concern for most of the year.

Heating degree-days, cooling demands, and insulation levels

In areas where air conditioning is a requirement for reasonable
comfort in summer, modification of the insulation-sizing formula is
necessary to take cooling costs into consideration. One way to
explain the costs for year-round climate control is:

Heating costs + Cooling costs = Climate control costs

To relate climate control costs to heating demand (i.e., heating
degree-days):

Climate control costs ÷ Heating costs x Heating DD = Climate
DD


If the winter heating bills total $200 and the summer cooling bills
total $200, the climate control costs are $400 for the year. Using
these values in the climate degree-days formula, we find that the
climate control costs are twice the utility costs expected by heating
degree-days alone.

$400 ÷ $200 x Heating DD = 2 x Heating DD = Climate
degree-days

To take these formulas one step further, the resulting climate degree-
days are plugged back into the insulation formula:

Climate degree-days x 0.004 = R-value needed.

Savannah, Georgia, energy utilization example. To illustrate the use
of these formulas, the actual 1984-85 heating and cooling costs of a
home near Savannah, Georgia, are used in calculations.
House features: 1,850-square-foot single-story ranch, slab on grade
with the following energy factors: walls: R-13; ceiling: R-35; floor:
no perimeter insulation; windows: double-glazed (aluminum frames with
no thermal break); north windows: 88 sq ft, south: 75 sq ft, east: 6
sq ft. The roof overhangs provide complete summer shading and 75%
exposure in winter.
During the 1985 summer months, the electricity rates rose, reaching a
net increase of $130 for the cooling season. During the 1984-85
winter, the gas rates rose, to a net increase of $110 for the heating
season. These figures are determined by calculating the average
electricity bills during months when air conditioning was not used.
This baseline cost is subtracted from the electric bills during months
when air conditioning was used. Gas costs for winter are similarly
determined by subtracting baseline gas usage from winter gas usage.
The cooling bill (central air conditioning) was about 18% greater than
the heating bill (central gas furnace). While this is comparing gas
heat and electric air conditioning, it still gives us some basis for
comparison. In using the formulas:

Heating costs + Cooling costs = Climate control costs
$110 + $130 = $240

Climate control costs ÷ Heating costs x Heating DD = Climate
DD
$240 ÷ $110 x 1,850
= 4,036

Climate degree-days x 0.004 = R-value needed
4,036 x 0.004 = 16, or R-16 needed for
the building

Summary: The Roggasch insulation sizing formula is accurate for cold
climates not requiring summer cooling. The above climate degree-days
formulas may be helpful in deciding the level of insulation needed for
year-round economy. The original insulation formula suggested that
R-7 was sufficient for the 1,850 degree-day example. However, when
cooling demands are considered, the insulation level should be about
R-16.

The example home in Savannah, Georgia, does not show utility costs
typical of the area. Usual heating and cooling rates are considerably
higher for neighboring homes. The house referenced is a new home,
meeting the regional criteria for energy conservation. It has
significant upgrades in attic ventilation and insulation; it has
radiant barriers in the walls although it lacks an attic radiant
barrier and vapor barrier. The house has nearly optimum solar
orientation, allowing passive solar gains in winter with complete
summer shading by the roof overhangs. Although its utility costs are
quite low for the area, they show the relative proportion of winter
versus summer utility rates. Such calculations can be carried out for
other geographical areas if heating and cooling bills are known.
In climates where the summer nights cool off, nighttime whole-house
ventilation can drop the temperature of the thermal mass of the house
to eliminate or reduce the need for daytime air conditioner use. If
an air conditioner must be used, nighttime usage is also more
economical due to the lower indoor to outdoor temperature extremes.

Other measures of insulation need

Essentially all insulation recommendations for use in the lower 48
states prescribe more insulation in the attic than in the walls or
floors. In winter, most homes have stratification of the air in the
house, meaning hot air is near the ceiling and the cold air is near
the floor. Hot air rises and cold air is produced by contact with
cold windows, walls, floors, and ceilings. The supply of cold air
from cold surfaces increases temperature stratification in homes.
Since the warmest air is near the ceiling in most homes, it makes
sense to have additional attic insulation to reduce heat loss. Floor
temperatures are usually moderated by the ground for slabs, crawl
spaces, and basements and do not need to be as heavily insulated as
the attic, except in severely cold climates. For well-insulated or
superinsulated houses stratification is less of a problem.
During summer, attic temperatures in the lower 48 states tend to rise
much higher than outside air temperatures, causing much heat gain
through the ceiling. This makes the house more uncomfortable and more
expensive to cool. By comparison, the ground usually moderates floor
temperatures unless the floor is over an open-air deck. An attic
radiant barrier, increased attic ventilation, and increased attic
insulation levels can reduce a significant portion of summer heat gain
in hot climates.
A 1983 publication from Canada recommends the following insulation
levels in southern Canada and the northern half of the Unites States:
ceilings: R-40; frame walls: R-30; foundation walls: R-20; and R-10
below the foundation floor.6 Another recent publication shows similar
recommendations for insulation in walls and ceilings, with R-30 to
R-16 for floor and slab insulation. (R-30 is used for slabs when the
floor is within 5 feet of a ground water source.) 23 The Minnesota
superinsulated house has R-46 for the walls, R-20 below the basement
slab, and R-70 loose fill in the attic.21


Heating Costs for the Year

Using the earlier calculations on winter heat loss, it is possible to
estimate fuel costs for the heating season. As shown earlier in this
book, insulation levels make substantial differences in heat loss in
cold weather. Heating systems and energy habits of the occupants also
make substantial differences. Occupants using 78° indoor temperatures
in winter use significantly more heat than when keeping a 62° inside
temperature. In most locations, electric heat is more expensive than
gas or oil heat.
To make some heating estimates, the below energy cost factors will be
used. (These calculations were based on prices as of 1990.)

1. Electrical resistance heat, at $0.07 per kilowatt hour (KWH), 100%
efficient, providing 3,413 BTU/KWH; the cost is $20.50 per million
BTU.
2. Gas heat, at $0.44 per 100 cubic feet; gas yields 1,000 BTUs for
each cubic foot; a 93% efficient furnace produces 930 BTU/cu ft, for a
net cost of $4.73 per million BTU.
3. Fuel oil, at $0.90 per gallon; each gallon yields 138,000 BTUs; 85%
efficient combustion provides 117,300 BTU/gallon, a net cost of $7.67
per million BTUs.

Actual energy prices have much variation throughout the country, and
over time, so separate calculations will be needed for current costs
in your area.

House examples from winter heat million BTUs electric heat oil heat
gas heat
loss calculations, for one day used/day costs costs costs

1 (uninsulated home) 1.619 $33.19 $12.41 $7.65
2 (normally insulated home) 0.538 11.03 4.13 2.54
3 (superinsulated, no heat exchanger) 0.262 5.37 2.01 1.24
4 (superinsulated with heat exchanger) 0.159 3.26 1.22 0.75
5 (example 4, with a sunspace) 0.127 2.60 0.86 0.60

The number of degree-days for a specific day is the average of the
high and low temperature subtracted from 65°. Example: with a high
of 35° and a low of 5°, there were 45 degree-days for that day ([35 +
5] ÷ 2 = 20; 65 - 20 = 45 degree-days). For the winter heat loss
calculations of the six example houses, the high was 20°F and the low
was -10°F, resulting in 60 degree-days for the day (20 + [-10] =
10; 10 ÷ 2 = 5; 65 - 5 = 60 degree-days).
In a 6,000-degree-day (DD) climate, 60 DD is about 1% of the cold
weather for the year. To estimate the fuel costs for the winter in
this climate, the heat used for the one day (60 DD) could be
multiplied by 100, indicating a gas heat cost of $765 per year for an
uninsulated house and $75 for a superinsulated house. In reality, a
6,000 DD climate does not have 100 days of weather described in the
example calculations. In fact, such temperatures might not even be
reached in an entire heating season. Instead, the heating season is
longer (about eight months long) and usually less severely cold.


Below is listed the heating degree-days for two different climates:
the 5,429 DD climate of Springfield, Illinois, and the 10,000 DD
climate of Duluth, Minnesota. The heating season is broken down into
degree-days for each month. The average temperature in each month
used in these calculations is the number of degree-days for that
month, divided by the number of days in that month, subtracted from
65° (This data is derived from Designing and Building a Solar House,
by Donald Watson.)

Springfield, Average Duluth, Average
Illinois, temperature Minnesota, temperature
Month degree-days in month (°F) degree-days in month (°F)

July 0 over 65° 71 63°
August 0 over 65° 109 62°
September 72 63° 330 54°
October 291 56° 632 45°
November 696 42° 1131 27°
December 1023 32° 1581 14°
January 1135 28° 1745 9°
February 935 32° 1518 11°
March 769 40° 1355 21°
April 354 53° 840 37°
May 136 61° 490 49°
June 18 64° 198 59°
Year Total 5,429 10,000

As explained above, the average temperature during each month can be
determined from the degree-days for each month using the formula:

65° - (DD ÷ Number of days in the month) = Average
temperature for month.

To calculate heat loss of a building, the temperature difference
between inside and outside must be determined. If the outside
temperature is 10°F and the inside of the house is kept at 70°F, there
is a 60° ∆T. For the 10° outside temperature, a 62° indoor
temperature results in a 52° ∆T, although a 78° indoor temperature
makes a 68° ∆T. In this way, the energy habits of the occupants can
have significant effects on the utility bills. For these
calculations, 70°F is used as the indoor temperature. Therefore, to
determine the ∆T in the calculations, this formula is used:

70° - Average temperature for the month = ∆T

The net heat requirement is calculated for each home type by this
formula:

Heat loss (in BTU/°F/24 hours) x ∆T, minus the solar and internal
gains for the day x Number of days in the month = Heat demand for
the month.

For these calculations, all house specifications are kept the same as
used in the example houses. The internal gains are kept at 36,000 BTU/
day. The solar gains are computed based on the latitude, percent
sunshine, and types of windows used in the example houses. The heat
loss is calculated based on the ∆T for the locations listed.

Sample calculation. House example 2 for Springfield, Illinois, has a
heat loss of 405 BTU/°F/hr; multiplied by 24 hours, this is 9,720 BTU/
°F/24 hrs; with 42° ∆T for January this is a loss of 408,240 BTU/24
hours. For an average 47% sunshine for the month, there are combined
solar and internal gains of 90,295 BTU/day. This leaves a net loss of
317,945 BTU/day. This is 9,856,295 BTU loss for the 31-day month, or
9.856 million BTU heat loss for January. In the two tables below,
combined solar and internal gains are listed for the example houses in
various months. Example 1 has single-pane windows, resulting in
greater solar gain than double-pane (example 2), or triple-pane
(examples 3 and 4). Example 5 has a south-facing sunspace, increasing
the solar gain.

Springfield, Illinois
Month % Sunshine Net solar and internal gains
(BTU/24 hours) for example houses
1 2 3, 4 5

September 73% 127,171 115,975 104,778 138,544
October 64% 120,542 110,160 99,777 138,630
November 53% 104,358 95,964 87,564 120,554
December 45% 91,632 84,800 77,968 105,266
January 47% 97,896 90,295 82,693 112,622
February 51% 106,150 97,535 88,920 121,303
March 54% 103,094 94,964 86,615 115,023
April 58% 93,252 86,416 79,357 99,899
May 64% 90,747 84,024 77,300 92,892
June 69% 93,252 86,221 79,190 94,591


Duluth, Minnesota
Month % Sunshine Net solar and internal gains
(BTU/24 hours) for example houses
1 2 3, 4 5

July 68% 106,117 97,507 88,896 112,061
August 63% 106,846 98,146 89,445 116,578
September 53% 103,322 95,055 86,787 116,055
October 47% 95,438 88,139 80,839 108,949
November 36% 74,570 69,834 65,097 84,150
December 40% 74,070 69,395 64,719 83,837
January 47% 87,517 81,191 74,864 100,394
February 55% 108,639 99,719 90,798 125,351
March 60% 115,638 105,858 96,077 131,232
April 58% 103,015 94,785 86,555 112,551
May 58% 96,668 89,218 81,767 102,074
June 60% 99,042 91,300 83,558 102,323

A superinsulated home can reduce the length of the heating season,
since heat is not needed until temperatures drop to low levels. To
illustrate this point, calculations are made for winter heat loss for
the six example houses. The heat demand is listed in the tables as
millions of BTU/month. The true heat consumption for a house depends
on the actual temperatures and amount of sunshine. In the following
examples, the calculations are based on long-term average heat demands
and expected sunshine for the locations listed (data derived from
Designing & Building a Solar House).

5,429 degree-day climate: Springfield, Illinois, for the six example
houses, using solar gain calculations based on 40° north latitude

Month ∆T 1 2 3 4 5

September 7° 1.814
October 14° 7.710 0.804
November 28° 19.085 5.286 1.869 0.538
December 38° 28.337 8.821 3.888 2.022 1.175
January 42° 31.425 9.856 4.405 2.342 1.415
February 38° 25.180 7.611 3.205 1.519 0.613
March 30° 21.404 6.099 2.292 0.819
April 17° 10.674 2.365 0.349
May 9° 4.570 0.128
June 6° 1.937

Million BTUs used/year 152.136 40.969 16.008 7.240 3.203

Gas heat costs/year $719.60 $193.78 $75.72 $34.25 $15.15

10,000 degree-day climate: Duluth, Minnesota, for the six example
houses, using solar gain calculations based on 48° north latitude

Month ∆T 1 2 3 4 5

July 7° 2.416
August 8° 3.215
September 16° 9.585 1.820
October 25° 17.539 4.801 1.642 0.415
November 43° 31.920 10.444 4.951 2.908 2.336
December 56° 43.677 14.723 7.285 4.535 3.942
January 61° 47.359 15.864 7.800 4.805 4.013
February 59° 40.689 13.265 6.299 3.682 2.715
March 49° 36.613 11.483 5.151 2.745 1.655
April 33° 23.100 6.779 2.702 1.134 0.354
May 21° 14.215 3.562 0.949
June 11° 5.735 0.469

Million BTUs used/year 276.063 83.198 36.779 20.224 15.015

Gas heat cost/year $1,305.78 $393.55 $173.96 $95.66 $71.02

When looking at the above data, one can see that normal insulation
uses only 30% of the space heating costs compared to an underinsulated
house (examples 1 and 2). Superinsulation (example 4 versus example
1) uses less than 8% of the space heating costs compared to an
underinsulated house. Adding a sunspace (example 5) seems to give no
more than $25 in space heating savings, compared to superinsulated
design (example 4). The addition of a sunspace, just to save heating
costs, is not cost-effective.
Existing technology provides other ways of reducing heating costs:
(1) by use of a sunspace, (2) R-60 walls and floor combined with R-70
ceilings, (3) quadruple pane east/west and north windows,

and (4) use of R-15 insulating shutters on the windows during the
night (12 hours/ night). The calculations below represent the net
heat needed for the 10,000 degree-day climate in Duluth, Minnesota,
for various insulation upgrades, using the same house size described
earlier.

Duluth, Minnesota, for the listed insulation upgrades
Shutters
Shutters Quad E/N
Sunspace Quad E/N Quad E/N Sunspace
Month ∆T R-60/70 R-60/70 R-60/70 R-60/70 R-60/70

November 43° 2.103 1.531 1.974 1.386 0.814
December 56° 3.452 2.859 3.266 2.474 1.882
January 61° 3.625 2.833 3.433 2.570 1.779
February 59° 2.652 1.684 2.515 1.761 0.794
March 49° 1.797 0.707 1.725 1.032
April 33° 0.516 0.531 0.080

Million BTUs used/year 14.145 9.614 13.444 9.303 5.269

Gas heat cost/year: $66.91 45.47 63.59 44.00 24.92

Adding shutters has only a $20 annual space heating savings in the
above examples. To eliminate the need for furnace heat, it would be
necessary to add at least 150 square feet of solar collectors on the
south wall for the final example house (shutters, quadruple pane east/
north windows, sunspace, R-60 walls, floors, and R-70 ceiling).
Avoiding any use of auxiliary heat requires extreme measures in this
cold climate and is not cost-effective at current energy prices.

Applications of Energy Technology to New Homes

Standard house insulation

Walls. The limiting factor for insulating standard walls is space.
With 3½" of space between the wallboard and sheathing, the amount of
insulation is usually R-11. Studs and framing take up 15% or more of
the wall area, resulting in a significant amount of wall conduction
and reducing the final insulative value of the wall to below the R-11
level. Using 2x6 inch framing, there is 5½ inches of insulation space
(R-19 batt) and the stud spacing can be wider, reducing the amount of
stud conduction. Rigid insulation board sandwiched either inside or
outside the stud framing increases the final insulation value.
External insulative sheathing can induce condensation problems within
the wall. However, vapor-permeable external foam boards with
perforated radiant barriers are available that do not induce
condensation when properly installed. A continuous vapor barrier is
very difficult to achieve with a standard wall (whether 2x4 inch or
2x6 inch framing) because wiring and piping pierce the vapor barrier
and allow air infiltration and water vapor leakage. In standard
construction, an infiltration barrier (Tyvek® or other housewrap) used
over the exterior sheathing reduces heat loss by reducing infiltration
and by preventing wind from blowing into the insulation. Infiltration
barriers are especially useful in houses where the builder did not use
a continuous vapor barrier on the inside wall.




Ceilings. Attics of standard homes usually allow sufficient space
for large amounts of insulation in the ceiling. Twelve inches (R-35)
to 24" (R-70) of loose fill insulation are often used in well-
insulated attics. Use continuous soffit vents, gable vents, and ridge
vents, or the equivalent, to provide ventilation needed to remove
attic moisture. The local building code usually specifies the amount
of vents used in the attic. Use no less than 1 square foot of open
vent space for each 300 square feet of attic. About 50% of the vent
area should be soffit vents; the remainder should be gable and/or
ridge vents. A vapor barrier should be provided on the inside surface
of the ceiling between the ceiling sheetrock and insulation to reduce
moisture migration into the attic. Alternatively, one can retrofit a
continuous attic vapor barrier. (See page 78 for suggestions about
retrofitting attic vapor barriers.)
Shed roofs, flat roofs, and some vaulted ceilings limit the space for
insulation and ventilation, sometimes to only 5½ inches. Even when
space is limited, ventilation is still necessary to remove moisture in
winter and excess heat in summer.
Conventional roofs usually have insufficient space for insulation and
ventilation over the top plate of the wall. Because of the typical
bird's mouth cut in the 2x6 roof rafter, the space over the top plate
is less than four inches. If insulation is not carefully installed,
the ventilation passageways over the top plate can be blocked and
attic condensation can occur. Changing the roof-framing design can
allow for proper ventilation and insulation depth over the top plates
in the attic.



A radiant barrier installed in the attic reduces radiant heat gain in
hot climates and radiant heat loss in cold climates. Insure plentiful
attic ventilation to remove excess summer heat and to reduce
overheating of the roofing material. A radiant barrier used in walls
also reduces heat loss and gain. A radiant barrier can be used at the
plane of the vapor barrier, or a perforated radiant barrier should be
used in exterior parts of insulated walls or ceilings, the
perforations allowing moisture to escape.


Floors. Basement walls and floors need insulation; the ground is not
an insulator. Insulation boards can be installed during construction
to cover all exterior surfaces of the basement. In milder climates,
it may be sufficient to use perimeter insulation. Heat escaping from
uninsulated basement walls reduces freezing of the ground near the
wall. When insulation is added to the wall, freezing of moist ground
near the basement wall can actually cause foundation cracks due to
ground expansion during freezing. Backfilling with gravel or reducing
moisture levels outside the wall can reduce frost damage to foundation
walls. Insulating basement walls interiorly increases the risk of
frost damage; because the concrete foundation conducts heat out of the
ground faster than the surrounding earth, freezing of the surrounding
ground is accelerated. When insulating interiorly, also add some
exterior insulation (e.g., rigid foam insulation) to reduce heat
conduction out of the ground through the basement walls.
The floor joists, often 9 to 12 inches in depth, above crawl spaces
usually provide ample space for insulation. Less insulation is
usually installed for the floor than the ceiling, since the warmest
air is near the ceiling. Floors and walls should have similar amounts
of insulation. In colder climates, the amount of heat lost from the
floor increases, requiring more floor insulation. Ventilate the crawl
space to remove moisture.
Windows. At least double-pane glass, with nonconductive framing,
should be used. Metal frame windows should be limited to types having
a thermal break. If there are no data to show that a thermal break is
provided in a specific metal frame window, no thermal break is likely
to be present. A proper amount of south windows should by used; in
most areas of the country, it is advisable to minimize east, west, and
roof windows, particularly important in the southern United States.
North-facing windows have little solar gain, and do not significantly
increase air-conditioning bills, but add to heating bills in winter.
South windows should have an appropriately-sized overhang to shield
the sun in summer and to allow solar gain in winter. (See the section
in part four covering overhang designs.)
Ventilation. The home will need a method of supplying fresh air when
there is an effective vapor barrier. Running bathroom exhaust fans
may or may not remove enough stale air for proper ventilation.
Opening windows may be needed to get fresh air or to feed the exhaust
fans. In some cases, it may be more economical to provide whole-house
ventilation by use of an air-to-air heat exchanger.
Having a poor vapor barrier risks internal wall condensation and
rot. An effective vapor barrier and good weather-stripping cause air
quality problems unless ventilation is otherwise provided for.
Piping. Even in southern climates, it is possible for water pipes to
freeze within exterior walls in winter. There is simply not enough
space in a 3½ inch external cavity wall to have enough insulation to
assure that pipes in these walls will not freeze, even if most of the
insulation is exterior to the pipe. There are numerous freezing
disasters in winter, even in the southern United States. Piping is
not always buried deep enough in the ground to be below the winter
frost line. It is common for pipes to run through the middle of
exterior walls, attics, crawl spaces, and above carports and garages.
Some outside faucets are not provided with inside shutoffs. When
pipes go through potentially cold areas they must be insulated
properly to prevent winter freezing and summer condensation.

Ducts. Ventilation ducts passing through unheated spaces should be
thoroughly insulated. These ducts can cause major losses of energy
due to the temperature extremes between the duct and the surrounding
areas. It is common for such ducts to have a thin foil-backed
insulation cover, not adequate to conserve energy. A 6-inch-thick
insulation blanket should be added to the ducts.

The superinsulated house

Walls. A backward double wall is most effective for superinsulation.
It provides the space for insulation, allows for a continuous vapor
barrier, and protects the vapor barrier for the lifetime of the
house. The insulation value used is dependent on the climate demands
of the area, as related to heating degree-days and cooling demands;
R-30 to R-50 is a range suitable for the northern United States and
southern Canada. Exterior insulative sheathing should be avoided to
prevent moisture condensation in walls. The backward double wall
technique allows the necessary insulation to fit into the exterior
wall cavity by either batt or loose fill insulation. The exterior
sheathing and siding should have at least 3 to 5 times the
permeability of the vapor barrier to prevent moisture condensation.
Overlap all vapor barrier junctions and seal the joints properly to
assure continuity of the 6 mil polyethylene vapor barrier. Pay
special attention to the vapor barrier near junctions of internal
partitions to obtain continuous ceiling and floor vapor barriers.
Insulation blankets should be installed at right angles for each
successive layer. For example, use an R-30 insulation roll in
horizontal layers in the central cavity of the double wall, then
install the R-11 batts vertically between the studs. Alternating
between horizontal and vertical insulation layers will minimize
convective air movements within the wall.




Ceilings. Enough attic space for 12 or more inches of insulation
should be provided. The more severe the climate, the more insulation
should be used. Wires, pipes, and ducts should be routed through the
walls and between floors so that the vapor barrier of the ceiling is
not broken. Alternatively, a continuous vapor barrier can be retrofit
in the attic (see page 78).
Provide at least 12 inches of insulation over the top plate of the
inside wall. The insulation of the attic should be continuous with
the insulation of the walls. If rolls or blankets of insulation are
used in the attic, install the layers at right angles. The first
layer is placed between the ceiling joists, and the second layer is
put at right angles to the joists, on top of the first layer of
insulation. Provide good attic ventilation to remove moisture.
Floors. There should be a continuous vapor barrier to prevent
moisture migration. Floors above crawl spaces should have amounts of
insulation similar to those of walls. Additional floor insulation can
be added by strapping and crosshatching techniques. The insulation
can be secured in place with insulation support netting. See the
section on retrofitting for other techniques to hold up the
insulation. The crawl space should be well ventilated to remove
moisture and to prevent the entry of radon from the ground. Moist
ground should be covered with 10-mil polyethylene.
Windows. Double- or triple-glazed windows provide reasonable energy
efficiency for south windows; plan to use triple-pane or low-E glass
for all other orientations. Use a suitable amount of south window
area for passive solar gains. The low-E glass coatings reduce heat
loss in winter and heat gain in summer by blocking infrared heat
waves. Low-E windows still allow passive solar heating, although they
block some of the solar energy transmission. Insulated shutters and
shades covering windows on cold nights can cut down on space heating
demands. Since windows are constructed to fit in standard wall
thicknesses, the additional thickness of a superinsulated wall
complicates the installation.

Window framing for superinsulated walls



The window can be mounted in the inside 2x4 inch framing or the
outside curtain wall framing or by beveling the casing to a position
in between the two points. The vapor barrier position seems better
when the window is at a more exterior position; this allows the proper
amount of insulation exterior to the vapor barrier joint. It is
possible to bevel the casing near one of the stud walls and then
attach an additional storm window to the framed space of the nearby
wall (inside beveled casing having a double-pane window and an outside
single-pane storm window).





If window shutters are desired, the shutters can be designed to fit as
a pocket within the superinsulated wall. Inside the wall and between
the windowpanes, the shutters are protected from inside condensation
and outside snow, rain, and cold. 2 (One opens the inside window to
operate the shutter, or the shutters can be hooked to pull cords to
open and close.)



Ventilation. It is necessary to provide fresh air for the house,
since infiltration has been nearly eliminated. It is best to route
bathroom and kitchen vents to a common point for attachment to the air-
to-air heat exchanger. The outside duct for air intake should be
positioned as far as possible from likely sources of contaminated air;
position it away from sources of car exhaust and fireplace emissions
and from the direct airflow of the heat exchanger exhaust vent.
Outside air can be economically preheated by the heat exchanger.
However, in very cold winter climates the exchanger core can
potentially freeze and not allow sufficient airflow for proper
operation. There are a few possible methods to defrost the exchanger
core. 1) Use a solar panel on the south wall to preheat intake air.
26 2) Have the intake air fan shutdown on a specific schedule to
allow the warmer exhaust air to thaw the core.27 3) Manually defrost
the exchanger by shutting down the exchanger and routing room air
through the exchanger until it thaws. 4) Install electrical
resistance heating coils in the intake air stream to defrost the
exchanger when necessary. There are various problems with these
methods: Cold days without sunshine will not allow the solar panel to
defrost the core. Shutting off one air stream causes air imbalance
throughout the house. Manual defrosting requires additional, more
complicated ductwork. Using an earth tube to pre-warm the exchanger
air could prevent frosting of the exchanger core, however, problems
with radon infiltration make this method unsafe.
Since the home is constructed very tightly, all combustion appliances
must have outdoor air supplied directly to them. Without direct air
supply, combustion air might be drawn through the exhaust flue,
returning dangerous gases to the house. Without direct air supply, a
fireplace would have difficulty removing exhaust and sustaining
combustion, putting occupants of the house at great risk from
contaminated indoor air.

To allow adequate circulation of ventilation air between rooms,
provide a one-half to one-inch space at the bottom of doors or install
vents in the room doors; this will assist the circulation of air
between the intake and exhaust vents of the heat exchanger duct
system.

Vent positions for air-to-air heat exchanger

Exhaust the air from bathrooms, kitchen, and laundry. Introduce fresh
air into all other rooms of the house for best distribution. Provide
a one-half to one-inch space at the bottom of inside doors to allow
ventilation air to circulate.

Provide supply and exhaust vents for the basement; if only exhaust
vents are provided for the basement, the negative air pressure can
actually cause increased radon gas infiltration. Providing positive
air pressure to the basement will in effect reduce radon
infiltration. Air should be exhausted from the kitchen, bathrooms,
and laundry room (if clothes are hung up to dry). New homes tend to
have more contaminants than older homes due to the paint, glues, other
chemicals, and moisture in new construction materials. Initially it
is a good idea to provide ventilation of 1.0 air changes per hour to
remove these contaminants. After the first year, the ventilation rate
could be decreased to 0.5 air changes per hour unless contamination
persists. Radon contamination may require higher airflow rates, used
on a permanent basis.
Radiant barriers. A radiant barrier can be placed at various points
in superinsulated walls. A radiant barrier can be placed within the
wall at the position of the vapor barrier or a perforated radiant
barrier used on the most exterior part of the wall. A radiant barrier
can be installed in ceiling insulation layers or attached to the top
chord of the roof truss. In order to reflect heat rays in winter, the
radiant barrier might be more effective if near the inside of the
house to prevent any of the radiant heat from being absorbed in the
attic. In hot climates the objective is to keep the heat radiation
from entering the home; the radiant barrier mounted on the roof rafter
or top chord of the roof truss is probably more effective.





For alternative locations of where to place radiant barriers (such as
in attics) see the diagrams on pages 17 and 18.

Provide plenty of continuous attic ventilation above the attic
radiant barrier to remove excess summer heat. A radiant barrier will
also prevent heat loss in winter through the floor above a crawl
space. Thus a radiant barrier can be installed appropriately within
the floor or a perforated radiant barrier can be installed on the
exterior of the floor insulation. Radiant heat is less intense,
although similar to microwaves in a microwave oven. In those ovens,
the door often has a window with a metal grid, perforated enough to
see through, yet the heat radiation is contained within the oven.
Similarly, a perforated radiant barrier reflects heat radiation yet
allows moisture to escape.
A reflective air space is necessary for proper performance of a
radiant barrier. If a reflective air space is not provided, some of
the reflected heat radiation is concentrated next to the surface of
the radiant barrier; the heat trapped in that area will be conducted
from the radiant barrier to surrounding building materials. These
surfaces can then re-radiate the received heat, even though the
radiant barrier itself does not radiate heat very well. For the same
reason, if the radiant barrier gets a layer of dust on it, the dust
can absorb and re-radiate the heat.
Piping. With a backward double wall, piping and wiring can be routed
freely through the inner wall, since they will not break the plane of
the vapor barrier. With R-30 to R-40 exterior to the inside wall,
there is no danger of freezing if water pipes are in the inner wall.
Avoid installing pipes in attics and crawl spaces. If water pipes
must be routed in these areas, they should be very well insulated. In
very cold climates, such as areas of Alaska, pipes going outdoors are
wrapped with heat-producing wires and then covered with thermal
insulation to prevent freezing.
Wiring. Wiring confined to uninsulated areas poses no problems.
However, various texts have conflicting comments about wiring buried
deep in house insulation. Electrical wires have resistance, which
produces heat. If the wires are run at more than their rated
capacity, the excess heat could be trapped near the wires and
potentially cause melting of the electrical insulation around the
wires, especially if the wires run through thermal insulation (e.g.,
insulation batts or loose fill). The heat is retained near the wires
and cannot dissipate, risking an electrical fire. Some texts state
that wires and heat-producing electrical fixtures should not contact
thermal insulation. The backward double wall can avoid this whole
problem without losing thermal performance of the building; the wires
can be routed safely through the internal wall and not contact the
thermal insulation. Wires routed through attics will have contact
with thermal insulation and could pose some risks.
Recessed lighting fixtures near thermal insulation have been
identified as potential fire hazards. One approach is to build (large
enough, wooden) boxes around the recessed lighting fixtures, to
provide the recommended (3”) air space. Then put the proper amount of
thermal insulation, exterior to the box that was built around the
lighting fixture.
Ducts. Heating and cooling ducts should be placed within the thermal
enclosure and not go through unheated spaces. If they must pass
through unheated spaces, they should be well insulated.

Methods of making a superinsulated wall

The backward double wall can be arranged to provide the insulation
level desired by separating the inside and outside wall to the
appropriate thickness. If the inside wall is the load-bearing wall,
the house can be built in the conventional platform method. The floor
joists are cantilevered to the projected position of the exterior
curtain wall.

Alternatively, the house is assembled in the normal fashion and the
curtain wall is attached to the original wall by ledger plates and
joist hangers. Pay special attention to the placement of the vapor
barrier so that it can be attached to the ceiling and floor vapor
barriers. The roof overhang must be wide enough all the way around
the house to allow for the thickness of the curtain wall. Design the
attic with enough space to hold the full depth of insulation over the
outer walls.




















One method is to modify an oversized roof truss to have the inside
wall as the bearing point -- the truss is cantilevered outward from
the load-bearing wall. With standard roof framing, an appropriately
sized overhang is designed, similar to an overhang used for a porch,
to allow sufficient insulation over the exterior walls and to provide
proper shading. See the section in part four describing methods for
determining overhangs for south-facing windows.
It is also possible to make an inside double wall instead of
cantilevering the backward double wall. In this method, the exterior
wall is assembled in the conventional fashion. Massive exterior
siding, such as brick or stone, can be used with this method, if
desired. When the exterior of the home is completed, the insulation
layers are put in place. The inside walls are assembled on the floor
with sheathing and vapor barrier and are tilted into place. If loose
fill insulation is used, the insulation is added after the inside wall
is put in place. This method might require using the next larger size
floor joists (e.g., 2x12 instead of 2x10 inch) since the inner wall
position adds one foot to the floor span; also, the weight of the
insulation and inside wall must be carried by the floor, requiring
greater floor strength. The piping and wiring are routed freely
through the inner wall, since they will not disturb the vapor
barrier.

Retrofitting Insulation in Existing Homes

Retrofitting is a relatively new term used to describe the process of
adding something formerly not present. Retrofitting insulation means
to add insulation to previously uninsulated or poorly insulated areas
of a building.
Compared to a home being constructed, an existing home is far more
difficult to insulate. The attic can be insulated when there are open
attic spaces. Shed roofs and cathedral ceiling roofs provide little
space for retrofitting insulation short of replacing the roof or
lowering the ceiling from the inside. Exterior walls are closed on
both sides with siding or wallboard, making retrofitting very
difficult. Basement slabs and slab on grade floors are already
poured; it is impossible to insulate under them. Aside from adding
attic insulation, no significant insulation is usually added after
completion of the building.
Adding insulation to existing walls will usually require some rather
extreme measures and is very expensive. Below are possible options
for wall retrofitting.

1. One option is to add insulation to empty wall cavities. However,
the blow-in or foam-in techniques have their disadvantages. The major
problem is the absence of a vapor barrier. With insulation added to
existing walls, the moisture that enters the wall will be retained in
the insulation, and eventually lead to rotting of the wall. Painting
the inside walls with two coats of a vapor barrier paint reduces
moisture penetration into the wall. This method of insulation is
limited to achieving the standard level of insulation. Another
problem with blow-in insulations is a tendency for the insulation to
settle. A specific adhesive (Blow-in Blanket®) uses special machinery
to mix it with blow-in insulations to reduce the settling. As the
adhesive cures within the first few hours, it causes the insulation to
harden into a solid mass.5

2. Another way is to construct new inside walls, adding insulation
between the original wall and the new inside wall. Adding insulation
interiorly requires replacing and moving electrical outlets and any
pipes in exterior walls; it disrupts life within the home due to all
the construction being done inside. It reduces the size of the
existing rooms. It becomes nearly impossible to get a continuous
vapor barrier.
3. If the house is in need of new siding, the cost of adding
insulation exteriorly may be reduced effectively. By adding
insulation exteriorly life inside the home is not disrupted, since all
the work and much of the noise are on the outside. To add insulation
exteriorly, the roof must have overhangs wide enough to allow for the
increased wall thickness. The space for the added insulation can be
relatively slight, as when framed by 2x2s or 2x4s; larger amounts of
insulation can be added by strapping and crosshatching layers of wood
framing and putting the insulation within the framed spaces. The
largest amount of insulation can be added with the least framing by
use of a curtain wall. The purpose of a curtain wall is to hold the
insulation in place and to keep the rain off. The curtain wall is not
a structural wall since the inside wall holds up the roof. The siding
applied cannot be a heavy material -- wood, aluminum siding, and
stucco are suitable. A continuous vapor barrier can be installed when
insulation is added exteriorly.
4. A house with a brick façade is very difficult to insulate
exteriorly. A curtain wall must be attached to a load-bearing
structure of the wall, foundation, and/or roof. Thus the ledger plate
would have to be attached by lag bolts through the brick veneer into
the internal wood frame of the building or anchored into the concrete
foundation. This method is far more difficult than directly bolting
to the load-bearing members of a house with wood siding. An
alternative approach for insulating brick exteriors is to anchor foam
boards to the brick. This method, however, will not be able to
achieve very thick levels of insulation.

Procedure for retrofitting exteriorly (curtain wall)

1. Make the curtain wall studs of the proper length to extend from
the sill plate to the roof rafters. Determine the thickness of
insulation the curtain wall is to hold. Attach the proper length
horizontal 2x4 inch member with plywood gussets to provide for the
appropriate wall thickness.
2. Remove the existing siding if it is either rotten or to be
reused. Remove the soffit covers. Use a continuous polyethylene
vapor barrier to cover the wall. Seal all joints of the vapor barrier
with overlapping folded seams (French seams) and secure the seam to
the wall with furring strips. Acoustical sealant or other long-
lasting caulk should be used to improve the air/vapor seal around
window, doors and other breaks in the vapor barrier. Additionally,
secure the vapor barrier in place with wood strips to prevent future
leakage at these breaks in the vapor barrier. TenoArm film is
preferable as a vapor barrier. However, the widely available 4-mil or
6-mil polyethylene does an excellent job if properly sealed. The
vapor barrier must then be covered to protect it from wind damage, UV
light, and other damage that could occur during retrofitting. After
sealing the vapor barrier, it can be protected by covering it with a
radiant barrier, building paper, or sheathing material.

3. Attach a 2x4 inch ledger plate to the frame of the house, using
lag bolts. Install joist hangers to the ledger plate at the spacing
needed for the curtain wall studs (see diagrams), 24-inch spacing for
the curtain wall studs is usually sufficient.
4. The curtain wall studs are mounted by the joist hangers on the
bottom and securely attached to the roof rafter at the top. The sole
plate of the curtain wall connects all curtain wall studs. Building
paper, tarpaper, or equivalent under the siding will help keep the
rain out. The plywood bottom and the exterior siding provide
sheathing strength for the exterior curtain wall.
5. Retrofit the basement walls either exteriorly or interiorly (see
page 69). To retrofit basement walls exteriorly, it is necessary to
dig a trench wide and deep enough to attach the vapor barrier and
install the exterior foam insulation boards. (Contact local utilities
to determine where it is safe to dig, and rent a backhoe to save much
labor in digging.) The vapor barrier and foam boards, 3 inches or
more thick, are installed all the way to the footings. Extended
perimeter foam boards, 3 inches thick, are added up to 4 feet away
from the foundation, not covering the drain tiles near the footings.
In milder climates, 4-inch-thick foam boards are installed to a depth
of 2 ft below grade and as extended perimeter insulation about 4 feet
away from the building. Cover the foam boards above ground with a
protective barrier -- metal flashing, special plastic covers, pressure
treated plywood, or special stucco material designed to cover foam
insulation boards. See manufacturer listings after the references.
6. The floor over a crawl space is insulated by applying the
insulation for the full depth of the floor joists. The vapor barrier
should face upward toward the inside of the house. The insulation can
be kept in place between the floor joists by a number of methods. 1)
Hold the insulation in place with insulation support netting, a weave
of nylon fibers sold in rolls covering 1,000 square feet. 2)
Sheathing material is the most expensive way to hold up insulation,
but perhaps the most durable. 3) Hold the insulation up with stiff
wires wedged between the joists; wires are sold for this purpose. 4)
Crisscross wire from nails at the bottom of the joists. 5) Cover the
insulation with chicken wire. 6) Cover the outside of the insulation
with Tyvek® (or other brand) housewrap to hold the insulation in place
and to keep wind out of the insulation. 7) Cover the insulation with
a perforated radiant barrier; perforations are necessary to allow
moisture to escape. The insulation support netting is economical and
strong and could be modified to hold up an extra layer of insulation,
using little additional framing. By having 2x2s attached to the floor
joists, additional insulation can be fitted between the bottom of the
floor joists and the insulation support netting. The ground of the
crawl space should be covered with a plastic moisture barrier if
required by code or if the soil tends to be moist. This prevents the
crawl space moisture from dampening the insulation. Be sure to
insulate any ducts and water pipes in the unheated crawl space.
Alternatively, it is possible to cover the walls and ground of the
crawl space with insulation and a vapor barrier instead of insulating
the floor above.23, 41

See pages 147 to 153 for practical details on retrofitting insulation.


















Part Three
HOUSE VENTILATION
Fresh Air for Tightly
Constructed Homes

Evaluating Air-to-Air Heat Exchangers

Integral to the fresh air needs of new, well-insulated homes is
ventilation to replace infiltration (which has been minimized).
Ventilation of cold outside air into the home is unpleasant if the air
is not heated in advance. When the outdoor temperatures are low, the
most economical method of getting fresh air is by use of an air-to-air
heat exchanger. This device has been also termed a Heat Recovery
Ventilator (HRV). In this text I will use the terms “air-to-air Heat
Exchangers,” or “Heat Exchangers” or Heat Recovery Ventilators (HRVs)
all to describe the same type of device.
Heat exchangers extract heat from the outgoing air and transfer it to
the incoming air. Although schematic diagrams of the exchanger make
it seem simple and inexpensive, quite the opposite is the case. As of
1989 prices, heat exchangers cost from $400 to $1,500. The price of
an exchanger is not necessarily related to heat recovery efficiency.
A heat exchanger is a relatively new product designed to fill a new
need. Many companies market various types of heat exchangers. It is
difficult to find the most suitable model with so many varieties to
chose from.

Counterflow and crossflow heat exchangers

There are two types of fixed plate heat exchangers: crossflow and
counterflow. These usually have parallel surface membranes between
which air is passed. Intake air is on one side of the plate, and
exhaust air is on the other side.



The counterflow exchanger routes the exhaust and intake air through
the exchanger in opposite directions.

By having a long course through which the air can travel, the heat is
readily exchanged between the two streams of air. A short distance of
air stream overlap usually means lower heat recovery. Some
counterflow models have very long heat exchange cores, up to 8 feet in
length, while other counterflow models have barely a 2-foot core
length. A short counterflow model can end up very efficient if it has
a lot of surface area for heat transfer. A long counterflow model
might have less surface area over a much longer distance.



The typical crossflow heat exchanger schematic diagrams show the air
streams passing at right angles to each other; significantly more than
60% efficiency cannot be expected. A single-pass crossflow exchanger
would require enormous amounts of heat-transfer area and a very slow
airflow rate to get high efficiency. Using the crossflow design,
higher heat recovery is more effectively obtained by a double-pass
crossflow core.



Double-pass crossflow models, routing the air in two passes through
the heat exchanger core before exiting, give better efficiency.
Single-pass crossflow models can be expected to get 50 to 55% heat
recovery, although some companies claim their single-pass models get
75% heat recovery. If the exchanger is made to have the air routed
through in a double-pass, the first pass recovers 53% of the heat and
the second pass through the other heat exchange element recovers 53%
of the remaining heat (0.53 x 0.47 = about 0.25). This results in
about 78% heat recovered for the two passes (0.53 + 0.25 = 0.78).
By lengthening the separation between the ports, the crossflow and
counterflow models begin to resemble each other. Indeed, there can be
combinations of the crossflow and counterflow designs.



The final efficiency of a heat exchanger is determined by a number of
factors: the arrangement of the heat exchange plates, the total
surface area available for heat exchange, and the rate of airflow. A
fast airflow rate will usually decrease efficiency. The actual
details of the internal airflow through the exchanger will help
determine the effectiveness. The heat exchange plates should be
impervious to air and moisture. There should be essentially no cross-
leakage, no mixing of intake and exhaust airflows.
Single-pass crossflow heat exchangers can be expected to have lower
efficiency than double-pass crossflow or most counterflow exchangers.
Counterflow and crossflow models can obtain better efficiency by an
increase of exchange area and by having a longer distance of air
travel within the exchanger core. Related to these fixed plate
designs are exchangers using tubes for the heat transfer surface.


Heat pipe type of heat exchangers



The heat pipe exchanger transfers heat from one stream of air to the
other by way of conductive pipes extending from the exhaust to the
intake air streams. Inside the heat pipes is some form of refrigerant
fluid, such as Freon, to transfer the heat from one side to the
other.

Rotary heat exchangers


The turning wheel picks up the heat from the outgoing stream and
transfers it to the cold stream about one-half rotation later.
Redrawn from "Heat-Recovery Ventilators," Consumer Reports (October
1985).

The rotary heat exchanger has a slowly turning heat recovery wheel
that picks up heat from one stream of air and transfers it to the
opposing stream about one-half rotation later. The rotary types range
from small home models with a 16-inch-diameter exchange wheel, to huge
industrial exchangers with up to a 13-foot-diameter exchange wheel.

The rotary exchange wheel transfers heat between the air stream as
well as transferring some moisture (and its latent heat). Recovery of
moisture, therefore, increases the overall recovery of heat. Rotary
types of heat exchangers must be engineered carefully to prevent cross-
leakage of air. As the wheel rotates from the exhaust air to the
clean air, some of the contaminated air can re-enter the building.
Most heat exchanger types recover "sensible heat" (heat that can be
sensed by touch or measured by a thermometer). "Latent heat" is the
heat of fusion or vaporization of water. If a home has air that is
too dry, using a humidifier to add moisture to the air will consume
additional heat to change the water into the vapor state. As water
vapor is recovered by an exchanger, the latent heat of vaporization is
also recovered. These types of devices have been termed Energy
Recovery Ventilators (ERVs). Not only do they recover “sensible heat”
but “latent heat” as well.
With very tightly constructed homes the objective is to remove
contaminated air and typically to remove excess moisture. Most heat
exchanger companies emphasize that their models allow no cross-leakage
of the two air streams and no moisture transfer. Rotary heat
exchanger companies and other ERV products emphasize that exchanging
moisture with the incoming air is a good feature of their product. It
is hard to know whether moisture removal or recovery is the better
feature for all applications. If the inside air tends to be too dry,
then moisture recovery is preferable. However, if the inside air is
already too humid, recovery of water vapor does more harm than good.
Heat Recover Ventilators (HRVs) are designed to recover sensible heat
and to exhaust accumulated moisture (which is most important for cold
climates). Energy Recovery Ventilators (ERVs) are designed to recover
latent heat as well, which is apparently more useful for air
conditioning in hot, humid climates.
The October 1985 issue of Consumer Reports included a review of air-
to-air heat exchangers. The Consumer Union obtained specific models
of exchangers to test for efficiency of heat recovery at two
temperatures (5° F and 45° F). Airflow capability, cross-leakage,
type of recovery unit, size, price, and overall ratings of five whole-
house units and two window models were compared. The rated
efficiencies were from 15% to 71% heat recovery. The best three units
were marginally acceptable (38% to 71%) even at their lowest airflow
rates (42 to 89 cubic feet per minute). Prices of the best three
units ranged from $540 to $1,161. The window/wall models had
approximately 50% efficiency, with an airflow capacity too low to be
effective for a superinsulated house. The performance of one
exchanger seemed extremely poor (15% to 19%). In general, Consumer
Reports recommended obtaining fresh air by using an exhaust fan or
opening windows; the cost of heating the ventilation air did not
justify use of a heat exchanger. A heat recovery ventilator was
recommended only under certain conditions: for extremely tight houses
in extremely cold climates or where unusual problems existed, such as
with radon pollution or chemical contaminants in the home.25
The problem with new, tightly constructed homes is that exhaust fans
alone cannot result in proper air quality. Since fresh air must be
introduced, the house is much more comfortable when the air is pre-
warmed. Calculations from the section "Heating Costs for the Year"
demonstrate the cost of heating fresh air with and without use of a
heat exchanger. The figures show the cost of heating ventilation air
without a heat exchanger to be about $80 per year using gas heat.
(Compare examples 3 and 4 for Duluth, Minnesota.) However, the same
size house without a heat exchanger, having a full-length basement,
and using 1.0 air changes per hour would have an annual cost for
heating ventilation air of over $300 per year. (Calculations are
based on gas heat @ $0.44 per 100 cubic foot; if only electric heat is
available, the annual costs would be over $1,000/year.) The following
factors affect the cost of heating ventilation air: the house size,
the ventilation rate, the coldness of the climate, and the cost per
BTU of heat. In the most extreme conditions, an air-to-air heat
exchanger can recover sufficient heat from exhaust air to save
hundreds of dollars per year, based on gas heating costs.

Considerable variation may exist between claimed and actual
efficiency of heat exchanger types. Different companies market
similar heat exchangers; if one company claims 75% efficiency and a
different company's comparable model claims 55% efficiency, it leads
one to doubt the claims.
Power consumption of the heat exchanger fans should also be
considered. For heat exchanger models operating continuously for 180
days per year, 65 watts power consumption will use about $20 worth of
electricity; 300 watts power consumption will use about $90 worth of
electricity (at $0.07 per kilowatt-hour).
Most companies provide accessories to improve exchanger performance.
Some models compensate for incomplete heat recovery by adding an
electric pre-heater. With such a device, the air going into the
house is heated to 100% of room temperature by electrical resistance
heat after it leaves the heat exchanger. One rotary model preheats
air going to the exchanger core to prevent core freezing when outside
temperatures are too low. Many models have a defrost cycle, and most
provide a way for condensed moisture to be removed from the exchanger.
The exchanger selected should be able to supply the fresh air needs
of the home (about 0.5 air changes per hour) on the lower speed fan
setting. As an example: a single-story 1,500 square foot house with 8
foot ceilings has 12,000 cubic feet of air, which is one air change
for this size house; half of that is 6,000 cubic feet. An exchanger
with a 100 cubic feet per minute (cfm) capacity would move 6,000 cubic
feet per hour. Larger quantities of contaminated air are removed by
switching the exchanger to the high-speed fan setting, especially
useful when combustion is taking place (cooking, smoking, or fireplace
use). Contaminated air is exhausted from the bathrooms and kitchen as
fresh air is introduced by ductwork into the other rooms of the
house. Ventilation standards from the American Society of Heating,
Refrigerating, and Air Conditioning Engineers, Inc. (ASHRAE),
recommend exhaust ventilation of 50 cfm capacity for bathrooms and 100
cfm for kitchens; this is usually supplied by manually operated
exhaust vents, used when the need arises. Continuous ventilation by
heat exchanger ducts provide less peak airflow although better
effective ventilation, since the occupants do not shut off the
ventilation system. ASHRAE further recommends a continuous fresh air
supply of 10 cfm to each room of the house.13 This is best achieved
by providing exhaust vents for the bathroom, kitchen, and laundry and
fresh air ducts for all other rooms of the house.
Most heat exchanger companies provide installation instructions for
the heat exchanger, including flow balancing. If the exhaust and
intake ductwork causes unequal resistance to airflow, the house will
be slightly de-pressurized (if outflow is greater) or pressurized (if
inflow is greater). Dampers in the ductwork must then be adjusted to
equalize the airflow. If unequal, there will be increased rates of
infiltration every time a window or door is opened, as well as driving
infiltration through any breaks in the vapor barrier.
Although there are heat exchanger models on the market that are well-
designed, efficient, and reasonably economical, it may be difficult to
find the most suitable model.
The following pages detail an exhaustive mailing research project I
did on air-to-air heat exchangers in 1988. Less than 2 years later, I
re-contacted the companies and found many had moved, changed names,
and changed products. Some had apparently completely gone out of
business, as I could find no forwarding address. (At this time in
life, it is possible to conduct an Internet search for such products,
for those companies that list their products on the “web.”)
Being a “do-it-myself” person, I felt I could do a good job designing
and making my own. In 1988, I figured how to make such a homemade
model from hardware store products.

Since late 1988 (though 2003), I have had my homemade heat exchanger
in use in my home. I have placed my “recipe” for my version in the
section of this book on homemade air-to-air heat exchangers.

Summary of Data on Commercially
Available Heat Exchangers

Comments about 1989 data: The following pages list a number of
companies marketing or manufacturing air-to-air heat exchangers.
During a 24-month period (1987-1989), I had witnessed significant
changes in the availability of products from some of the companies.
New products were added, formerly available products were deleted,
companies changed hands, and some companies went out of production.
This is not intended to be an all-inclusive list of every exchanger
type available; the listed data are subject to change over time and
with market forces.
Abbreviations: s.p. crossflow = single-pass crossflow; d.p.
crossflow = double-pass crossflow; Cross/counter = exchanger may be
rated by the company as one model or the other, although the airflow
pattern, judged by diagrams received from the company, appears to be a
combination of the two different types of flow, i.e. a short
counterflow model resembles a crossflow model and an elongated
crossflow model may be partially counterflow. Power Used = electrical
power in watts (W) or amperes (A) used by the fan motors with the fan
on the high setting. Some of the smaller exchanger models use one
motor to turn two centrifugal blower wheels for the exhaust and intake
air streams. In larger-capacity units, invariably two motors are
needed and the power consumption increases. Some of the models locate
the blower motors within the air stream, so heat given off by the
motor is added to the fresh air stream, raising the exchanger
effectiveness. The designation N/A = a value not applicable. N/A
is used to refer to cores only, which have no fans, thereby no power
consumption quantity can be assigned. Most airflow rates listed are
values with no resistance from ductwork; as ductwork is added,
resistance is added. One exchanger rated at 140 cfm reduces to 119
cfm with a moderate amount of air resistance (e.g. 0.4" static
pressure). Efficiency ratings are from company literature. Some
companies explain the efficiency at various airflow rates, outside
temperatures, and inside relative humidity; other companies state only
one efficiency rating. One heat exchanger company claims 70%
efficiency, but when tested by Consumer Reports was given an
efficiency rating of 38 to 55%. 25 The buyer should be cautious and
not necessarily accept heat recovery claims as completely accurate.

September 2003 comments: I did a search for “Heat Recovery
Ventilators” on the Internet. I also did a search of the companies I
listed from 1989. Of the 17 listed companies for 1989, there were
still several of the same names, still manufacturing Heat Recovery
Ventilators (HRVs). There may be others of these companies from 1989
that do not have a functional web-site, or have changed their name. I
found more than a dozen other HRV companies (within the first 100 web-
sites I searched), which are listed below. There were over 4,000
entries that I found on my Internet search for “Heat Recovery
Ventilators.” These Internet entries included manufacturers,
suppliers, installers, and general information on the topic.
I believe that by studying my text on this subject (and also
reviewing the data on the HRVs from 1989), you can understand the
theories of how air-to-air heat exchangers work. This can help you
understand the basic types and forms of these devices, and be better
able to know what you are looking at when investigating the products
of specific companies.
Heat Recover Ventilators (HRVs) are designed to recover sensible heat
and to exhaust accumulated moisture (which is most important for cold
climates).
Energy Recovery Ventilators (ERVs) are designed to recover latent
heat as well, which is apparently more useful for air conditioning in
hot, humid climates.


The following are HRV and ERV companies I found on my Sept 2003
Internet search.

1. Airxchange; 85 Longwater Drive; Rockland, MA 02370; Ph:
781-871-4816. Markets rotary HRVs. (See this company under my 1989
listings.)
2. American Energy Exchange, Inc.; 5737 East Cork Street; Kalamazoo,
MI, 49048; Ph: 269-383-9200. Markets large capacity HRVs (1,000 cfm to
30,000 cfm “heat wheel recovery” (rotary version), flat plate versions
(single and double-pass crossflow HRVs with aluminum cores) and heat
pipe versions.
3. American Aldes Ventilation Corporation. (See this company under my
1989 listings also.) Markets single-pass and double-pass crossflow
HRVs with aluminum cores.
4. Broan. Markets single-pass crossflow HRVs. Phone: 1-800-558-1711;
Broan-NuTone, LLC.; P.O. Box 140; Hartford, WI 53027. (See my
listings for this company under ventilation products, pg 142-144.)
5. Bryant Heat Recovery Ventilators. (No technical details of the
products were shown on the web-site.) (esshvac.com)
6. Carrier makes two different versions of ERVs for residential use.
These appear to be single-pass crossflow cores, designed for enthalpic
energy and moisture recovery. Carrier is a widely-know company with
dealers throughout the USA.
7. Chester Dawe. Markets at least one type of HRV (KMH-150 Heat
Recovery Ventilator). Many locations in Canada. One such address:
1297 Topsail Road; P.O. Box 8280; St. John's, NF; A1B 3N4; (709)
782-3104
8. Chris Smith HVAC, Inc. Markets HRVs with single-pass aluminum
crossflow cores. (cshvac.com)
9. Cleanaire. Markets single-pass crossflow HRVs. Avon Electric
Ltd.; Christchurch, New Zealand. Ph 0800 379247
10. Eco Air 56 Bay Road; Taren Point, NSW 2229; Australia. Markets
counterflow HRVs with aluminum core. Ph: 61 2 9526 2133
11. Fantech; 1712 Northgate Boulevard; Sarasota, Florida 34234;
1-800-747-1762. Markets single pass crossflow HRVs with polypropylene
core
12. Grantair Technologies; 1470, Rome Blvd.; Brossard; (Quebec) J4W
2T4; Canada. Markets residential HRVs and other products.
13. Heatilator Home Products; Hearth & Home Technologies; 1915 W.
Saunders Street; Mt. Pleasant, IA 52641; (877-427-8368). Markets
single-pass crossflow HRVs with aluminum cores and models of ERVs.
14. Honeywell makes two different versions of single-pass crossflow
HRVs with aluminum cores and crossflow ERVs. These are marketed and
installed by various companies, which can be found by Internet search
under Honeywell HRVs.
15. Kiltox Damp Free Solutions; 27 Park Row; Greenwich SE109NL; United
Kingdom. Markets HRVs.
16. Lifebreath – appears to be single-pass crossflow HRVs with
aluminum core. Indoor Air Quality Distributors; 83 Galaxy Blvd., Unit
19 ; Toronto, Ontario M9W 5X6; Canada (416) 674-7525; 1-877-839-3036
17. Newtone Home Heat Recovery Ventilators, ph 800-525-7194. Appears
to be single-pass crossflow cores with “enthalpic transfer” (moisture
absorbing/transmitting exchange plates).
18. Nu-Air Ventilation Systems; Newport, Nova Scotia; Canada, B0N
2A0; (902) 757-1910. Markets HRVs, which appear to be single-pass
crossflow cores (aluminum or plastic, depending on the model).
19. Raydot, Inc.; 145 Jackson Avenue; Cokato, MN 55321; 800/328-3813
or 320/286-2103. Markets HRVs for agricultural, industrial, and
residential uses. (See this company under my 1989 listings.)
20. RenewAire (formerly Lossnay). Markets HRVs, which appear to be
single-pass crossflow HRVs with moisture absorbing/transmitting
exchange plates. Sound Geothermal Corporation; Rt. # 3 Box 3010;
Roosevelt, UT 84066; ph 435-722-5877
21. Summeraire. Markets residential HRVs. Appears to be single-pass
crossflow design.
22. Venmar Heat Recovery Ventilators; Thermal Associates; 21 Thomson
Ave.; Glens Falls, NY 12801; 1-800-654-8263; 518-798-5500. Markets
HRVs, which appear to be single-pass crossflow, with a polypropylene
core.
23. Xetex, ph. 612-724-3101. Markets flat plate heat exchangers
typically with aluminum cores and rotary models. (See this company
under my 1989 listings.)

Summary of Data on Commercially Available Heat Exchangers (January
1989)

Company Type of Maximum % Heat Power 1989
Model no. core capacity recovery used Length Height Width Price

ACS - Hoval (Numerous aluminum crossflow cores also available in many
sizes)
PC-130-140 s.p. crossflow 140 cfm 60-75% 120 W 47" 18" 12" $920
PC-130-250 s.p. crossflow 250 cfm 60-75% 213 W 47" 18" 12" $1137
PC-230-140 d.p. crossflow 140 cfm 75-90% 120 W 67" 18" 12" $1238
PC-230-250 d.p. crossflow 250 cfm 75-90% 213 W 67" 18" 12" $1457

Air Changer Marketing: See Memphremagog listings

AirXchange
Model 570 rotary 70 cfm 75-80% 55 W 22" 13" 7.5" $438
Model 502 rotary 200 cfm 75-80% 145 W 29" 17.5" 10" $578

American Aldes
VMP H3/5 cross/counter 140 cfm 70% 1.75 A 53.5" 20" 11.5" $979
VMP H4/8 cross/counter 180 cfm 70% 1.75 A 53.5" 20" 11.5" $1015

Aston Industries (many sizes of aluminum cores are available)
Thermatube 2300
(core only) counterflow 200 cfm 70% N/A 57.5" 25" 8" $220
Aston 2000 exhaust ventilator
(blower only) N/A 1.3 A 18" 14" 12.5" $290
Aston 2412
(core only) s.p. crossflow 150 cfm 52% N/A 12" 12" 12" $290
Two Aston 2412
cores (no blower) d.p. crossflow 150 cfm 77% N/A $580

Berner Air Products
AQ Plus+ counterflow* 165 82% 370W 28" 17" 11" $820
* This is not a standard counterflow unit. see the text narrative on
Berner for details.

Cargocaire
Large industrial-sized heat exchangers available in the rotary style

Crown Industries (EZE-Breathe exchangers formerly sold by Ener-Quip,
Inc.)
RHR 100 cross/counter 100 cfm 70% 48 W 46" 8.3" 14" $682
RHR 200 cross/counter 200 cfm 70% 58 W 46" 11.3" 18" $764
RHR 400 cross/counter 400 cfm 70% 72 W 46" 14.3" 26" $999

Des Champs Laboratories
Series 175 window model 75 cfm $357
EZV-210 counter/cross 150 cfm 75% 0.8 A 46" 19" 14" $735
EZV-220 counter/cross 240 cfm 73% 1.5 A 46" 19" 14" $795
EZV-240 counter/cross 430 cfm 72% 3.0 A 49" 19" 18" $970
EZV-310 counterflow 145 cfm 85% 0.8 A 58" 19" 14" $805
EZV-320 counterflow 220 cfm 84% 1.5 A 58" 19" 14" $880
EZV-340 counterflow 415 cfm 83% 3.0 A 61" 19" 18" $1100

Enermatrix
EMX 10 s.p. crossflow 103 cfm 75% 2.11 A 28" 18" 13" $399
EMX 15 s.p. crossflow 103 cfm 75% 2.11 A 28" 18" 13" $429
EMX 20 s.p. crossflow 121 cfm 75% 2.11 A 28" 18" 13" $479
EMX 25 d.p. crossflow 250 cfm 80% 2.42 A 60" 18" 13.5" $899

Company Type of Maximum % Heat Power 1989
Model no. core capacity recovery used Length Height Width Price

Memphremagog and Air Changer Marketing
DR-150 counterflow 120 cfm 76% 84 W 60" 25" 15" $950
DR-275 counterflow 200 cfm 78% 260 W 66" 30" 15" $1130

Mountain Energy & Resources, Inc. (makes heat pipe exchangers
similar to QDT, Ltd.)
MER-150 heat pipe 160 cfm 70% 100 W 24" 24" 7" $585
MER-300 heat pipe 235 cfm 70% 180 W 26" 32" 13.5" $1085

NewAire
HE-1800c s.p. crossflow 70 cfm 73% 55 W 18" 18" 13" $420
HE-2500 s.p. crossflow 110 cfm 78% 120 W 30" 20" 12" $535
HE-5000 s.p. crossflow 210 cfm 78% 240 W 30" 20" 21" $795

QDT, Ltd.
SAE-150 heat pipe 150 cfm 70% 236 W 29" 22" 12.5" $629

Raydot
RD-225-H counterflow 225 cfm 63-82% 240 W 96" 17" 8" $846
RD-150-H counterflow 150 cfm 66-82% 150 W 96" 17" 8" $728
RD-90-H counterflow 90 cfm 71-86% 90 W 92" 9" 9" $629
RD-225-V counterflow 225 cfm 61-78% 240 W 14" 59" 14" $867
RD-150-V counterflow 150 cfm 63-79% 150 W 14" 59" 14" $752

Snappy ®; Standex Energy Systems
MA 110 s.p. crossflow 110 cfm 77% 50 W 17.5" 17.5" 7.5" $550
MA 240 s.p. crossflow 240 cfm 70% 100 W 22" 23" 8.5" $597

Star Heat Exchangers
Nova counterflow 70 cfm 65% 34 W 25" 16" 7.5" $307
Model 165 counterflow 165 cfm 80% 66 W 39" 12.5" 15" $620
Model 200 counterflow 200 cfm 80% 66 W 39" 25" 15" $770
Model 300 counterflow 300 cfm 80% 132 W 39" 25" 15" $960

Xetex
HX-50 s.p. crossflow 51 cfm 62% 74 W 11.5" 19" 7" $395
HX-150 d.p. crossflow 119 cfm 80% 80 W 18" 24" 12.5" $788
HX-200 d.p. crossflow 182 cfm 80% 120 W 25.5" 24.5" 12.7" $902
HX-250 d.p. crossflow 279 cfm 80% 125 W 18" 32" 22" $1242
HX-350 d.p. crossflow 377 cfm 80% 157 W 25.5" 40" 22" $1533

Air-to-Air Heat Exchangers:
List of Selected Commercial Companies
January 1989
ACS-Hoval, 935 Lively Boulevard, Wood Dale, IL 60191-2685, (312)
860-6800 or (800)323-5618. Markets a number of sizes of crossflow
heat exchangers. The exchangers and cores are constructed of aluminum
plates. The joints are sealed so as to prevent any cross-
contamination of the two air streams. The standard high-efficiency
models are a single-pass crossflow design rated from 60-75%. The
ultra-high-efficiency models route the air through the exchanger in a
double-pass crossflow pattern, raising the efficiency to between 75
and 90%. The standard efficiency models are rated at 140 cfm
(PC-130-140,
120 watts) and 250 cfm (PC-130-250, 213 watts). Both standard models
have total dimensions of 47" x 18" x 12" (including blowers).

(ACS-Hoval, continued): The ultra-high-efficiency models are rated at
140 cfm (PC-230-140, 120 watts) and 250 cfm (PC-230-250, 213 watts).
Both ultra models have total dimensions of 67" x 18" x 12" (including
blowers). ACS Hoval also makes heat exchange cores for other
commercial and home applications, with dozens of potential sizes
available. Their heat recouperators are made to be mounted in exhaust
ducts from ovens and furnaces to recover up to 75% of the heat from
these high-temperature exhaust gases. Prices: PC-130-140: $920;
PC-130-250: $1,137; PC-230-140: $1,238; PC-230-250: $1,457.

Air Changer Marketing, 1297 Industrial Road, Cambridge, Ontario
N3H-4T8, Canada, (519) 653-7129. Markets two different models of
counterflow heat exchangers (DR2000 series). See Memphramagog write-
up for the details.

AirXchange, Inc., 401 VFW Drive, Rockland, MA 02370, ph (617)
871-4816. Manufactures rotary type heat exchangers. Rotary-wheel
cores are available in interchangeable sensible and enthalpy
(dessicant-coated) versions. Enthalpy wheels are recommended for
cooling applications and for heating applications where retention of
some humidity is desirable. Model 570: 80% heat recovery; 22¼ " x 12
5/8" x 7½ "; 70 cfm capacity; 55 watts; 4-inch ducts; available in
wall-mounted and ceiling-mounted units. Model 502: 75% to 80% heat
recovery; 29" x 17½ " x 10"; 200 cfm capacity, 145 watts; whole house
unit for floor, ceiling, or basement installation; 7-inch ducts; a
variety of accessories such as grilles, airflow balancing grids, and
intake/exhaust fittings are also available. Depending on the
exchanger features and the accessories selected, the prices for these
exchangers are: Model 570: $438 - 623; Model 502: $578 - 917.

American Aldes Ventilation Corporation, 4539 Northgate Court,
Sarasota, FL 34234, (813) 351-3441. Markets heat exchangers of a
combined counterflow and crossflow airflow pattern; 70% heat recovery
at 90 cfm; polyvinyl chloride parallel plate core; condensate drain;
core size 38.5" long x 20" x 11.5"; 160 square foot exchange area;
blower unit is 15" x 15" x 18" with 6-inch ducts and 1.75 amps. Model
VMP H3/5: 90 cfm or 140 cfm fan setting. Model VMP H4/8: 130 or 180
cfm fan setting. Other, more sophisticated heat exchangers are
available (VMP-I). A simpler heat exchanger is available (VMP-A).
The exchanger kits include self-balancing airflow controllers that
provide constant airflow and eliminate the need to balance the airflow
for the house. The company also carries other types of heat exchanger
cores, exhaust ventilators, and numerous accessories. The listed
prices typically include most of the accessories needed for
installation. Prices: VMP H3/5: $979; VMP H4/6: $997; VMP H4/8:
$1015; VMP-A: $667; VMP-I 5/7: $1,395.

Aston Industries, Inc., P.O. Box 220, St-Leonard d'Aston, Quebec,
Canada, JOC-1M0, (819)399-2175. Markets aluminum crossflow cores and
a counterflow heat exchanger core (Thermatube 2300). The counterflow
(thermatube) heat exchanger vents the stale air through glass pipes in
the exchanger. The incoming fresh air is made to pass around the
glass pipes to pick up the heat. Capacity is up to 200 cfm, with up
to 70% heat recovery, has drain for condensate. Dimensions: 57.5"
long x 25" x 8". The Thermatube 2300 uses the Aston 2000 ventilator
module as the blower source for exhaust; 1.3 amps. It apparently does
not use a blower for the fresh air return; the return air must enter
by the negative air pressure created by the exhaust fan. The aluminum
crossflow cores (Aston 2400 series) can be obtained in 150 different
sizes from the smallest size: 12" x 12" x 4" (40 to 160 cfm) to the
largest size: 48" x 48" x 84" high (up to 24,000 cfm). The aluminum
crossflow cores can be hooked up serially to get a double-pass
arrangement, if desired. A basic crossflow core will have about 52%
heat recovery. With two cores hooked up in a double pass arrangement,
the efficiency rises to 77%. Prices: Thermatube core: $220; Aston
2000 blower: $290; Aston 2400 core: $290.


Berner Air Products Inc., P.O. Box 5410, New Castle, PA 16105, (800)
852-5015 or (412)658-3551. Berner previously marketed rotary heat
exchangers, but has switched to a counterflow model, the AQ Plus+.
Different from other counterflow exchangers, the AQ Plus+ routes
supply air through the exchanger core for a 3-second time period; it
then reverses the airflow sending exhaust air through the exchanger
core for another 3 seconds. The counterflow element is constructed of
aluminum foil with a hydroscopic coating for latent-heat (and
moisture) recovery. In addition to the counterflow heat exchanger
element, the unit employs three filters to eliminate indoor air
pollutants and allergens. The unit continuously filters (and returns)
the room air while performing the separate functions of exhausting a
portion of the room air and supplying fresh air. The unit is sold as
a "through-the-wall" installation. It has a variable speed blower,
ranging from 60 to 165 cfm; 370 watts maximum; 27.5" x 17" x 11"; 82%
heat recovery on the high setting. Price: AQ Plus+: $820.

Cargocaire Engineering Corporation, Senex Division, 216 New Boston
Street, Woburn, MA 01801, (617) 933-9010. Markets large capacity
industrial heat recovery systems of 500 cfm to 40,000 cfm; rotary
type, with rotary heat exchange element that can be 2.3 to 14 feet in
diameter; 75% heat recovery; all units too large for home use.

Crown Industries, 2101 E. Allegheny Avenue, Philadelphia, PA 19134,
(215)423-8900. This company markets three different sizes of heat
exchangers of a combined counterflow and crossflow design, having
aluminum heat exchange plates: EZE-BREATHE heat recovery ventilators
RHR 100, RHR 200, and RHR 400 (these exchangers were formerly marketed
by "Ener-quip", Inc). All have about 70% heat recovery, with two
fans, filters, condensate drain, and necessary controls. RHR 100:
100 cfm airflow; 48 watts; 46" x 8.3" x 14", with 4-inch ducts. RHR
200: 200 cfm airflow; 58 watts; 46" x 11.3" x 18", with 5.5-inch
ducts. RHR 400: 400 cfm airflow; 72 watts; 46" x 14.3" x 26", with 9-
inch ducts. Prices: RHR 100: $682; RHR 200: $764; RHR 400: $999.

Des Champs Laboratories, Inc., Box 440, 17 Farinella Drive, East
Hanover, NJ 07936, (201)884-1460. E-Z-VENT heat exchangers. Markets
more than 8 different home models of heat exchangers, counterflow (but
a relatively short core length); aluminum heat exchange elements; 2-
speed blowers; filters; condensate drains. Series 175 exchangers
are rated at 75 cfm for single-room use. Series 200 models: 3 models
ranging from 150 cfm to 430 cfm; 72 to 75% heat recovery; 24-inch
length of core; with blowers, the full dimensions are: 46" x 19" x
14" (smaller size) to 49" x 19" x 18" (larger size); large amount of
exchange area is compacted into the core (286 to 382 square feet).
Series 300 models: 3 models ranging from 145 to 415 cfm; 83% to 85%
heat recovery; 36-inch core length; with blowers, the full dimensions
are: 58" x 19" x 14" (smaller size) to 61" x 19" x 18" (larger size);
430 to 574 square feet exchange area. The company plans to market a
new model: EZ Vent II, 24" x 26" x 17", 240 cfm, $695. The company
also makes other models for commercial use of 615 to 2,200 cfm
capacity. Prices: Series 175: $357; EZV-210: $735; EZV-220: $795;
EZV-240: $970; EZV-310: $805; EZV-320: $880; EZV-340: $1,100.

Enermatrix, Inc., P.O. Box 466, Fargo, ND 58107, (701)232-3330.
Markets single-pass crossflow and double-pass crossflow heat
exchangers, polypropylene core, with filters. EMX-10: 18" x 13" x
28" (including blowers); 75% heat recovery; exhaust motor is of
greater airflow than intake (113 cfm versus 90 cfm); 2.11 amps total;
has condensate drain for both air streams; 4-inch duct size; no
defrost cycle (apparently not needed with the faster outgoing air).
EMX-15 & EMX-20 are the same size as EMX-10, but they have balanced
airflows between intake and exhaust, auto defrost control. EMX-15:
90 cfm; EMX-20: 113 cfm. EMX-25: separate blower housing (14" x 24" x
11") with 6-inch duct connections to exchanger core (35" x 18" x 13");
80% heat recovery; airflow is balanced between intake and exhaust
(about 250 cfm); 2.42 amps total; condensate drain; variable fan speed
control; dehumidistat control; auto defrost control. Prices:
EMX-10: $399; EMX-15: $429; EMX-20: $479; EMX-25: $899.

Memphramagog Heat Exchangers, P.O. Box 456, Newport, VT 05855, (802)
334-5412. Markets two different models of counterflow heat exchangers
(DR2000 series); core made from a polypropylene polymer (coroplast,
apparently); condensate drain; core size 50" long x 25" high x 15"
thick, having 280 square feet of exchange area; cold air ducts are 6-
inches in diameter; automatic defrost. To the basic core is added one
of two different warm end panels containing the blowers and controls.
The Model 150 has axial fans and 6-inch ducts; 60 cfm or 120 cfm fan
settings; 84 watts; this provides 76% heat recovery at 117 cfm and
outside temperature of 32° F; dimensions: 10" long x 25" x 15". Model
275 has centrifugal fans with 7-inch oval ducts; 120 cfm or 200 cfm
fan settings; 260 watts; this provides 78% heat recovery at 117 cfm
and outside temperature of 32°F (at -13°F, the heat recovery is 57%
for these models). Dimensions 16" long x 30" x 15"; the heat of the
motors raises the intake temperature further, giving an overall energy
performance effectiveness of 81 to 94%. The manufacturer lists that
under 2 or 3% cross-leakage can occur with these models. There is
apparently no moisture transfer with these models. Prices: Model
150 (DR-150): $950; model 275 (DR-275): $1,130.

Mountain Energy & Resources, Inc., 15800 West 6th Ave, Golden, CO
80401, (303) 279-4971. Heat pipe exchanger with lower fan power
consumption than the QDT model: MER 150: 24" x 24" x 7"; 70% heat
recovery; 100 watts total; 160 cfm at 0.25" static pressure. MER 300:
26" x 32" x 13.5"; 70% heat recovery; 180 watts total; 235 cfm at
0.25" static pressure. Prices: MER 150: $585; MER 300: $1,085.

NewAire, 7009 Raywood Road, Madison, WI 53713, (608)221-4499.
Markets three single-pass crossflow heat exchangers. HE-1800c: 18" x
18" x 13"; 70 cfm; 55 watts; 6-inch duct connections; 73% heat
recovery; filters; no condensate drain required. HE-2500: 30" x 20" x
12"; 110 cfm; 120 watts; 6-inch duct connections; 78% recovery at
110cfm; resin-coated paper core by Mitsubishi or optional polyethylene
core; filters; can order condensate hook-ups as an option. HE-5000:
30" x 20" by 21"; 210 cfm air streams; 240 watts; 8-inch duct
connections; resin-coated paper core or optional polyethylene; 78%
heat recovery at 210 cfm; condensate drain as option. Prices:
HE-1800c: $420; HE-2500: $535; HE-4000: $795.

QDT, Ltd., 1000 Singleton Boulevard, Dallas, TX 75212-5214, (214)
741-1993. Markets one model of a heat exchanger with a heat pipe type
core. SAE 150 150 cfm on high; 236 watts power consumption; 29" x
22" x 13"; 70% heat recovery; 6-inch duct connections; condensate pan
and overflow connection. Price: SAE 150: $629.

Raydot Inc., 145 Jackson Avenue, Cokato, MN 55321, (800) 328-3813 or
(612) 286-2103. Markets five heat exchangers of the counterflow
design; three are designed for horizontal installation (e.g. basement
ceiling) and two are designed for vertical installation. These
exchangers typically use aluminum heat transfer plates 0.024" thick.
The exchangers get the highest efficiency ratings (78 to 86%) at the
slowest airflow rates and the lower heat recovery ratings (61 to 71%)
at the fastest airflow rates. Blower speed is controlled using a
variable speed control switch, sold as an accessory. The typical
exchanger core has two large intake heat exchange chambers and one
exhaust chamber instead of multiple narrow chambers that can freeze in
winter. The 90 cfm model (RD-90-H) has a cylindrical exhaust chamber
and a cylindrical exterior. The company sells the basic core and
mounting straps at a specific list price; the final price will depend
on the size and type of blowers and accessories selected. Basic core
prices: RD-225-H: $498; RD-150-H: $468; RD-90-H: $385; RD-225-V: $519;
RD-150-V: $492. There are no listed prices for exchangers complete
with blowers. However, by adding the price of the basic core to the
price of two of the typical size blowers used, the following are
examples of the basic exchanger prices with blowers: RD-225-H: $846;
RD-150-H: $728; RD-90-H: $629; RD-225-V: $867; RD-150-V: $752.


Snappy ® Division, Standex Energy Systems, Box 1168, 1011 11th
Avenue S.E., Detroit Lakes, MN 56501, (800)346-4676 or (218)847-9258.
Markets two single-pass crossflow heat exchangers; May-Aire model MA
110: 110 cfm maximum capacity; 50 watts; 77% heat recovery; 17" x17" x
7.5"; 5-inch diameter ducts; condensate drain; defrost cycle. May-
Aire model MA 240: 240 cfm maximum capacity; 100 watts; 70% heat
recovery; 22" x 23" x 8.5"; 6-inch diameter ducts; condensate
drain; defrost cycle. Prices: MA 110: $550; MA 240: $597.

Star Heat Exchanger Corporation, B109 - 1772 Broadway Street, Port
Coquitlam, British Columbia, V3C-2M8, Canada, (604) 942-0525.
Markets three different sizes of counterflow heat exchangers having
interfaced tube cores and one small size of flat plate exchanger. All
models have an auto defrost cycle, axial fans with infinitely variable
speed control, and filters. The company rates the heat recovery
efficiency as the best when the outside temperature is the lowest.
Nova is the smallest model: maximum of 70 cfm; 34 watts; 65% heat
recovery; 25" x 16" x 7.5"; flat plate exchanger core; defrost cycle.
All other models have counterflow plastic tube cores. Model 165: 165
cfm; 66 watts; 80% heat recovery; 39" x 15" x 12.5"; 7-inch ducts;
defrost cycle. Model 200: 200 cfm; 66 watts; 80% heat recovery; 39" x
15" x 25"; 6- and 8-inch ducts; defrost cycle. Model 300: 300 cfm;
132 watts; 80% heat recovery; 39" x 15" x 25"; 8-inch ducts; defrost
cycle. Prices: Nova: $307; Model 165: $620; Model 200: $770; Model
300: $960.

Xetex, Inc., 3530 East 28th Street, Minneapolis, MN 55406, (612)
724-3101. Markets one single-pass crossflow and several double-pass
crossflow heat exchangers ("Heat X Changer" units). Made with
aluminum heat exchange plates. A basic crossflow model (HX-50) gets
about 62% heat recovery. Other double-pass crossflow models get 80%
heat recovery (HX-150 @ 119 cfm, HX-200, HX-250, and HX-350 @ over 350
cfm). The basic model (HX-50) is very compact (19" x 11.5" x 7") with
4-inch ducts. The double-pass models get progressively larger as the
airflow capacity increases. (HX-150 is 24" x 12.5" x 18" with 4-inch
ducts; HX-350 is 40" x 25.5" x 22" with 8-inch ducts.) On all
models the two streams of air are completely separated, with no cross-
contamination. Complete with condensate drain. Filter accessories
available. Prices: HX-50: $395; HX-150: $788; HX-200: $902; HX-250:
$1,242; HX-350: $1,533.

Notes on power consumption. The listed wattage on heat exchanger
models can be converted to the annual electrical costs in operating
the system using these formulas: Watts x hours of operation x
days operating per year ÷ 1000 = the number of kilowatt hours (KWH)
consumed per year. KWH/yr x your local electrical cost per KWH =
the total electrical cost per year.
For exchangers with only amperes listed the electrical costs can not
be as easily determined. For most electrical circuits, Watts =
Volts x Amps. However, this relationship does not hold true for
electric motors. The following quote from the book Wiring Simplified
should clarify the energy consumption relationship: "The amperage
drawn from the power line depends on the horsepower delivered by the
motor -- whether it is overloaded or under-loaded. The watts are not
in proportion to the amperes (because in motors, their 'power factor'
must be considered). As the motor is first turned on it consumes
several times its rated current, momentarily. After it comes to speed,
but is permitted to idle, delivering no load, it consumes about half
its rated current. Rated current is consumed when delivering its
rated horsepower, and more current if it is overloaded." 39
The wattage, then, can be as little as 50% of “Voltage x Amperage.”
Some heat exchanger data lists both amps and watts for the motors; in
these cases, the usual proportion is about 75% of voltage x
amperage. As an example, a reasonable estimate of power used by an
exchanger motor rated at 2.42 amps is 218 watts, as shown below.

Amps x volts x 0.75 power factor
= Approximate wattage
2.42 amps x 120 volts x 0.75 power factor = 218
watts

Air-to-Air Heat Exchangers: Homemade Models

A commercial air-to-air heat exchanger can be expensive. There are
methods to fabricate a heat exchanger with the needed materials,
mechanical skill, and time. The complete cost of materials for a
homemade whole-house heat exchanger can be half of the cost of an
equivalent commercial model. Making an air-to-air heat exchanger
requires extensive work in the time spent gathering the assorted
materials and assembly of all the parts. In addition, it may be
difficult to produce final performance comparable to some of the well-
designed commercial models. If not properly made, any retail model
will be better.

History of homemade heat exchangers

As energy costs rose, new ways were found to build homes having far
less space heating demands. Due to the nearly airtight construction
used in these new homes, indoor air tends to rapidly become stale.
Before long, techniques were being devised to provide fresh air for
energy efficient homes by recovering heat from the exhaust air.
Commercial models of air-to-air heat exchangers were not initially
available, so individuals and groups began to design heat exchangers
for residential use.
In the late 1970s, the Mechanical Engineering Department at the
University of Saskatchewan, Canada, designed a heat exchanger using
polyethylene vapor barrier as the exchange material. The polyethylene
sheeting was wrapped around plywood spacer strips to form a parallel
plate counterflow exchanger. Over the years, they designed two
different models of this exchanger. The first model used ½-inch thick
strips of pressure-treated plywood. The later model used 5/16 - inch
plywood and acoustical sealant to prevent moisture from entering the
edge of the wooden spacer strips. In the second model, each exchange
plate had a net size of 84" x 21", providing about 340 square feet of
internal surface area for the 28 exchange plates. The exchanger was
about 8 feet in overall length x 2 foot wide by 10 inches thick.
In 1985, the same group in Saskatchewan published a design (Solplan
6) of a new exchanger made from a rigid plastic sheeting material
called coroplast. Coroplast is a double-wall sheet of rigid plastic.
The air is made to flow through the spaces within the coroplast for
one air stream; air is passed on the outside of the coroplast for the
other stream of air. The homemade coroplast exchanger is a crossflow
core, with the exhaust air routed in a double pass through the
exchanger. The design is far more compact than that of the earlier
counterflow model, with the final size of the core about 36 x 36 x
12 inches.
Polyethylene sheeting as used in the original counterflow model lacks
rigidity. When the fans force air through the exchanger, the
polyethylene exchange plates tend to billow and close off the air
passageways unless the plastic is stretched very tightly during
installation. Polyethylene exchange plates tend to cause very high
internal air resistance when both blowers are operational. This
requires much electrical power to get reasonable airflow.




Coroplast is far superior to polyethylene for use as heat exchange
plates. Unfortunately, coroplast is not widely available. It is
manufactured in Canada in 4 x 8 foot sheets about ¼-inch thick. The
size makes it difficult to order coroplast by mail when not locally
available. A number of commercially available models use coroplast as
the exchange medium, having exchanger cores of single-pass and double-
pass crossflow as well as counterflow designs.

An additional homemade design for air-to-air heat exchangers
(as designed by the author of this book)
This text describes a homemade counterflow heat exchanger using
aluminum flashing as the exchange plate material. As a heat exchange
medium, aluminum is superior to plastics since it has a conductivity
hundreds of times higher, allowing good heat transfer with less
surface area. Plywood strips can be used as spacers for the aluminum
plates. Use plywood about ½-inch thick, cut in strips 1-inch wide,
cut to the proper lengths. Seal the edges of the plywood with
acoustical sealant or equivalent to prevent moisture from entering the
edges of the wood. By its nature, plywood could eventually rot from
the moisture condensing in the exchanger core even when sealant
protects the wood. Plastic lumber can be used as spacer strips (one
can find information on plastic lumber by a search of the internet).
When I designed this heat exchanger in 1988, I used a brand of plastic
garden "bender board" – which was likely one of the first types of
plastic “lumber” – I used it instead of plywood spacer strips. Bender
board was available where I lived at that time (California, in 1988),
but I never found it again after I moved to the east coast of the US.
Plastic bender board, intended to be placed in the ground as edging
for gardens, is resistant to both cold and moisture. Bender board
comes in 40-foot rolls, about 3¼-inch wide x ¼-inch thick. To provide
support and spacing for the aluminum sheets, a 1-inch width of the
bender board is sufficient. The roll can be cut into 1-inch widths
and the needed lengths with a table saw. Each roll then provides
about 120 feet of 1-inch strips. The exchanger design is a parallel
plate counterflow design about 5 feet in length, with 21 aluminum
exchange plates.

Homemade air-to-air heat exchanger core materials list:
(Materials list from 1988)
4 rolls of plastic bender board. ("Plastiform" Lawn and Garden Bender
Board, durable redwood grained plastic, manufactured by Kerber
Associates, Inc., 1260 Pioneer Street, Brea, CA 92621, (714)
871-2451) . . . . about $10 per roll. (Another brand is "Durex"
bender board, although it has a less smooth surface and an irregular
thickness, perhaps not allowing for a good air seal; manufactured by
Duraplex, Peterson Resource Company, Orange, CA 92667.) Or use an
equivalent amount of plastic lumber to have spacer strips about ½”
thick. If you can’t get ½” thick plastic lumber, you might still get
reasonable heat recovery using the more commonly available 1” thick
plastic lumber as spacer strips. Such an exchanger would use less
aluminum (due to half the number of exchange plates). (Using 1” thick
plastic lumber should make it easier to seal at the ports.)
2 rolls of 50-foot long aluminum flashing. The 14-inch width is
perhaps the minimum width that should be used. The 20-inch width will
provide 50% more exchange area for a larger-capacity airflow.
Flashing is also manufactured in 24- and 28-inch widths, although most
hardware stores may not stock the wider sizes.
5 pounds of 1 ¾ - inch (5d) galvanized box nails
½ pound of 1-inch (2d) galvanized box nails
2 tubes of silicone sealant
One box of staples ½ inch or longer and staple gun. (More nails can
alternatively be used instead of staples, although staples make it
easier to hold parts of the exchanger in position during assembly.)
Pop rivets or sheet metal screws for assembling sheet metal sections
10 feet of rigid angle metal (½ x ½-inch, to form the rigid metal
attachment flange)
1 or 2 hose or tubing connectors as condensate drains (3/8 to ½ inch
in diameter)
4' x 8' sheet of rigid insulation, ¾ to 1½-inch thick.
One large section of sheet metal (perhaps 3 foot x 10 foot in size) –
cut to specific dimensions to cover the exterior of the exchanger
(alternatively, plywood can be used).
Additional remnants of sheet metal (to make endplates and expansion
chambers)
30 feet of 1 x 1 inch sheet metal angle strip. (Alternatively, 1½ x
1½ - inch size can be used)
Sheet metal duct pipe, 6 inches in diameter. Four duct pipe sections,
at least 4 inches long each, will be needed. Two of the sections
should have a tapered end. To directly install duct booster fans in
the pipe, two of the sections should be made about 8 inches long. If
tapered ends are desired for each connector, then four original duct
pipes are needed.

Procedure. Cut the rolls of bender board into 1-inch-wide strips.
The plastic strips cut and nail similar to wood, although they are far
more flexible and difficult to handle when cutting. Make the
following lengths of the 1-inch-wide strips:

51" long strips 80 needed
8" long strips 80 needed
14" long strips 4 needed (for the outer layer on each side)
50" long strips 4 needed (for the outer layer on each side)



I tested my heat exchanger design, and found it had about 72% heat
recovery.
(The inside house / exhaust temperate is 68° F; the outside
temperature is +8° F. The incoming air is pre-heated to 51° F. Inside
to outside: 68°-8° = 60° ΔT; intake air pre-heat: 51° - 8° = 43° ΔT;
43° ÷ 60° = 71.6% recovery)

NOTE. Consider using plastic lumber, potentially cut from ½” thick
material, to serve as the spacer strips. If ½-inch thick plywood is
used instead of plastic bender board, then 40 strips of 51-inch length
and 40 strips of 8-inch length plywood will serve as spacers.
Alternatively, if the exchanger is made 3 inches shorter, 48-inch long
plywood strips with 51-inch long exchange plates could be used. The
edges of the wood must be caulked to block condensed moisture from
entering the wood in order to prevent later rotting. Wrapping the
plywood strips with 6 mil polyethylene could also prevent moisture
from entering the edges of the wood; it will still be necessary to use
sealant at the edges of the plywood strips to keep moisture from
getting around the polyethylene into the ends of the wood strips.
Pressure treated plywood might alternatively be used.

Cut the aluminum flashing into 54-inch lengths (each sheet will be 54
x 14 inches for the small size exchanger). Each aluminum roll will
make 11 plates; 21 plates will be needed for the exchanger. There is a
one-inch overlap of the aluminum plates at the port ends of the
exchanger to allow the aluminum plates to be folded together when
sealing the ports; the plates are 54 inches long and the plastiform
laminations are only 52 inches long.



Each exhaust lamination is two layers of plastiform thick; each
intake lamination is also two layers of plastiform thick. The
resultant air space is nearly ½ inch on either side of each exchange
plate.
The exchanger is assembled in sandwich fashion: an exhaust
lamination, an aluminum exchange plate, an intake lamination, an
aluminum plate, an exhaust lamination, an aluminum plate, et cetera.
It is difficult to get the first few layers started, since one is
connecting exhaust laminations to intake laminations through an
aluminum plate, not providing enough thickness for nailing until there
are at least 5 layers of plastiform strips. To get the process
started, attach an intake and exhaust layer on either side of one
aluminum plate by way of ½ inch staples. After 5 layers of
plastiform, the 2d nails can be used. Once there are 9 layers of
plastiform, the 5d nails can be used.
Using 1” thick plastic lumber should make it easier to seal at the
ports. The aluminum could be bent over and nailed to the adjacent
plastic lumber, perhaps taking less time and effort than the above-
described “rolling and flattening” of the aluminum plates. (This
process is described in the above diagram, and in more detail in the
diagram on page 102.)






Continue by alternating the laminations of exhaust and intake
plastiform. Always use an aluminum plate in between each double layer
of plastiform strips. While staples are convenient in holding the
plastiform strips in place temporarily, it will be necessary to use 5d
nails every 3 layers of plastiform strips to hold the exchanger core
together. The nails should be spaced about every 1.5 inches along the
plastiform strips to ensure a fairly good air seal, but do not use
nails through the 5" spaces reserved for the ports. Stretch the
aluminum plates and plastic strips tightly when stapling in place to
prevent bunching up the materials. Continue the assembly until there
are a total of 10 intake laminations and 10 exhaust laminations.
There are 19 exchange plates between the laminations and 2 plates on
the outside of the exchanger, for a total of 21 plates. The 19
internal plates provide the heat exchange surface. The outer plates
are secured in place by the 14-inch and 50-inch plastiform strips,
using a nailing pattern similar to the earlier layers. Be careful not
to nail through the 5-inch spaces reserved for the ports. The
thickness of the central core will be about 9 inches. There is a
possibility of some air leakage through the layers of plastiform
strips; a tight nailing pattern will minimize leakage out the sides.
Near the ends of the exchanger where plastiform strips attach at right
angles there is more possibility for leakage; the outside of the
exchanger should be caulked along these joints. As a finishing touch,
the two plastic sides of the exchanger can be covered with aluminum
flashing, requiring two more sheets of flashing, about 52 inches long
each. With the sides of the aluminum sealed under the final
plastiform strips and the ends caulked at the expansion chambers, any
air or moisture that leaks between the plastiform strips will be
trapped in that space and will not allow further leakage.
The ports are sealed by the following procedure: (1) Cut away a
section of aluminum between the ports; (2) fold the aluminum around
the plastiform strips to leave a clear opening for each port; and (3)
caulk the edges of the folded aluminum to prevent air leakage from the
opposing air stream.



The aluminum flashing material might have a coating of oil on it from
the factory. If desired, you could clean off the metal surface before
or after assembly. After I completed my basic exchanger core, I
soaked the exchanger in a large container of soapy water to dissolve
the oil and any dirt introduced during assembly. (Actually I filled a
large garbage can with soapy water, soaking the core, one end at a
time, to dissolve the oil. Then I rinsed thoroughly with a garden
hose to remove the soapy water.)






When the central core is completed, an expansion chamber is attached
to both ends of the exchanger. Two pieces of sheet metal will be
needed, 5 by 50 inches in size. These are wrapped around the port
ends of the core to make a rectangular tube, holes are drilled through
the sheet metal, and the expansion chamber is nailed to the
plastiform perimeter at each end of the exchanger. Another piece of
sheet metal (4 x 10 inches) is installed as a septum to divide the
exhaust and intake airflows. The septum is formed by making ½ inch
folds on two ends. (The final septum size is 4 x 9 inches for a 9-
inch thick exchanger core). Where the septum contacts the exchanger
between the ports the seal can be made more secure by cutting a score
line (with a hacksaw) in the plastiform and setting the septum in the
groove before sealing with caulk. All the internal joints of the
expansion chamber and septum must be caulked to prevent air leakage
and cross-leakage. Attach rigid angle metal to the perimeter edge of
the sheet metal and to the septum to allow for attachment of the end
plate at a later time. The end plate will hold the two duct pipes and
the condensate drain. Rigid insulation covers the central core; sheet
metal or plywood covers the exterior of the exchanger. For best
results, the exchanger made from 14-inch wide exchange plates should
have 6-inch-diameter ducts; 4-inch-diameter ducts will provide
sufficient airflow for only 100 cfm capacity. Careful measurements
are necessary when making the endplates, since the spacing is very
tight.
Once the exchanger is assembled, it must be hooked to the appropriate
duct connections for fresh air supply and exhaust air removal; fans
are attached to move air through the exchanger. Theoretically, if the
home is tightly constructed, when air is exhausted fresh air
automatically will be drawn in through the fresh air ductwork of the
exchanger; hooking up bathroom and kitchen exhaust fans to the
exchanger would serve this purpose. By exhausting air (without active
fresh air supply), a negative air pressure is created in the home,
potentially increasing radon infiltration as well as driving
infiltration through any break in the vapor barrier. In practice,
most exchangers have both exhaust and intake fans.



Air movement can be provided by a twin centrifugal blower (both air
streams moved by one motor) or by separate axial fans or centrifugal
blowers. The fans can be built into the warm end of the exchanger
instead of directly attaching the endplate, or a separate blower
housing can supply the air to the exchanger through ducts. Commercial
heat exchangers use either detached fan modules or built-in fans.
Either method is suitable for this exchanger, depending on the
preference of the builder. I found that the easiest method is to use
"duct boosters" in the duct connections next to the endplate. See the
listing of fan and blower suppliers after the references.
Filters should be installed to reduce dust accumulation in the
exchanger. (See page 153 for updated details on filters for this
homemade exchanger.) For up to 200 cfm airflow, 10-inch x 10-inch
filters, installed in the duct system before air reaches the exchanger
core, should provide adequate filtering.

The filter housings can be homemade from sheet metal or plywood, with
duct connections on both sides of the filter housing. There are
filter accessories from heat exchanger companies for this exact
purpose. (See product listings.) In the bathroom and kitchen provide
exhaust ducts for the exchanger. In the kitchen use a re-circulating
range hood with a grease trap instead of venting directly to the
exchanger; the exchanger duct in the kitchen removes the exhaust. The
clothes dryer should be vented directly outdoors; lint from the dryer
would quickly clog the exchanger. There are some indoor dryer vent
diverters sold for use with electric clothes dryers. These diverter
switches are used during winter to put the dryer heat (and moisture)
in the house instead of putting it outdoors. If this diverter is
covered by a nylon mesh, most of the lint can be trapped before
getting into the house air. (e.g., Cover the diverter with one "leg"
from a section of nylon hosiery to catch most of the lint that would
otherwise be expelled.) The moisture released will tend to raise the
humidity in the home excessively. If there is an effective heat
exchanger system, the moisture will be removed within a few hours.
(Author’s comment: When I tried venting dryer air inside my house, I
found an increase in mold/mildew deposits on paper products stored
near the laundry area. This occurred even with the presence of the
air-to-air heat exchanger. I believe that venting a dryer indoors it
usually a bad idea, even if an air-to-air heat exchanger is used in
the house.)
Under no circumstances should a dryer vent diverter be used with a
dryer burning fuel for its operation. (The combustion by-products
must be expelled outdoors.)
The pre-warmed fresh air should not be routed directly into the cold
air duct of the furnace. (It should be ducted no closer than 10
inches from the cold air inlet of the furnace.) If the heat exchanger
air is directly ducted into the furnace air plenum, the furnace fan
would make the airflow through the exchanger dangerously out of
balance, since the furnace fan is far more powerful than the exchanger
fans.27 The air from the heat exchanger should be distributed to all
rooms of the house for best air circulation, such as by putting ducts
through open cavities of internal walls, floors, and ceilings. If the
fresh air is brought to only one point, new air will not be obtained
in rooms away from the fresh air supply.13
The fans used to run the heat exchanger should be able to move the
needed amount of air without overworking the motor. Some axial fans
are not strong enough to move air against much resistance, whereas
most centrifugal fans are better able to maintain airflow despite
moderate resistance. For the size exchanger described in this text,
up to 150 cfm will give reasonable efficiency. An airflow rate of 150
cfm will provide 0.5 air changes per hour for a two-story home, 1,125
square feet per floor, with 8-foot ceilings. (150 cfm x 60 minutes =
9,000 cubic feet per hour. 1,125 sq ft x 8 ft ceiling x 2 floors =
18,000 cubic feet of house air. 9,000 cubic feet per hour ÷ 18,000
cubic feet per air change = 0.5 air changes per hour.) In a well-
sealed house, infiltration may supply 0.1 air changes per hour. Thus
to obtain 0.5 air changes the exchanger need supply only 0.4 air
changes per hour.
Higher flow rates are possible with this exchanger. However, the
port openings will cause significant airflow resistance. There are 10
ports for exhaust and intake, each 5 inches long and 7/16 inches
wide. This leaves only 22 square inches of open space for the air to
enter the exchanger for each direction of flow. Six-inch duct pipes
allow 28 square inches for airflow. (4-inch duct pipe provides only
12.5 square inches cross-sectional area.) Most axial fans cannot
force more than 150 cfm through a 22 square inch space, although
centrifugal blowers may have the power to nearly double the airflow
rate. Unfortunately, substantially increased electrical power is
needed to run centrifugal blowers.

Using 20-inch-wide aluminum flashing to make the exchanger, the port
openings will be 8 inches long, providing a 35-square-inch area for
the 10 laminations of exhaust and intake. This would allow nearly 250
cfm airflow rates with axial fans. Alternatively, using more
laminations of the 14-inch-wide exchanger plates will allow higher
airflow rates.





Under very cold outdoor conditions, moisture can freeze on the
exchange plates in the exhaust air stream; if sufficient ice
accumulates, the exchanger will be unable to function. Defrosting can
be accomplished by turning off the heat exchanger (requiring a very
long time for the core to thaw out) or routing air at room temperature
through the exchanger when the cold air fan is off. Solplan 6
suggests that defrosting can be done automatically by having the
intake air blower hooked to a 24-hour timer. The timer will shut off
the cold air blower on the schedule set on the timer. If the outside
temperature is above +14°F, no defrosting is needed. With outside
temperatures at 0°F, a 30-minute shutoff every 24 hours is
sufficient. At -40°F, a 30-minute shutoff every 12 hours will allow
defrosting. During the defrost mode, the warm air from the house is
still being exhausted. The heat of the exhausted air will serve to
defrost the frozen core.27 Under ordinary conditions (when the house
is closed up during cold or very hot weather), the heat exchanger
should be run continuously at the flow rate needed to provide fresh
air. (Usually 0.4 to 1.0 air changes per hour is sufficient.) Wiring
the exchanger to a humidistat is not correct, because the inside
humidity level is not necessarily an indication of the level of indoor
air pollution.
During mild weather, it may be preferable to open the windows for
ventilation, instead of using the heat exchanger. If the exchanger is
to be used to pre-cool hot, humid air in summer, there may be
condensation on the intake air passageways. For this reason, a
condensate drain can be installed on the warm air end of the exchanger
for summer use. However, I have found in 14 years of use in my house,
in hot, humid summers, that condensation is not an issue on the warm
air end of the exchanger.
The final efficiency of the exchanger will be better if the exchanger
is made thicker, using more exchange plates. Having 50% more exchange
plates will allow 50% more airflow with no loss of efficiency. It is
also possible to make single layers of plastiform (exhaust and intake
spacers) to separate the exchange plates; doing this will use 41
aluminum plates, doubling the exchange area (and doubling the cost of
the aluminum). However, with single layers of plastiform, the spacing
will be so tight that sealing the ports (by rolling the aluminum
plates) will be very difficult.

The exchanger can also be made wider (20 to 28 inches instead of 14
inches) to provide greater exchange area and airflow capacity. When
making the exchanger wider than 14 inches, it is necessary to increase
the port length to allow more airflow. (For a 20-inch exchanger
width, use 8-inch ports; for 28-inch exchanger width use 10- to 12-
inch ports.) There should be at least a 2-inch overlap of the
plastiform strips between the ports to allow adequate space for
nailing. With a port size larger than 8 inches, it may be very
difficult to fold the aluminum plates to make the port openings as
described in the diagram "Sealing the ports of the heat exchanger."
The force needed to roll that amount of aluminum is probably more than
the 3/16-inch steel rods can withstand.



In constructing the basic core of the 14-inch-wide exchanger, the
assembly time was about 30 hours and the cost of material was $220,
plus the fan costs. See the product listings for possible sources of
blowers and fans.
The ductwork of the exchanger system goes through the exterior walls
for fresh air intake and exhaust air removal. The sections of duct
pipe going through the wall should have a shield to keep out the rain
and a screen to keep out insects and birds. Position the fresh air
duct away from possible sources of contaminated air (away from car
exhaust, fireplace smoke, septic vent pipes, and the exhaust duct of
the heat exchanger).



Although 4-inch duct vents (as used for clothes dryers) going through
exterior walls can be obtained for several dollars, the 6-inch sizes
usually cost substantially more.

If the exchanger and duct connections do not cause equal airflow
resistance, flow balancing between the two air streams is necessary.
The air streams are balanced by installation of dampers in the exhaust
and intake exchanger duct pipes within the house.



Test and adjust flow balance on a calm day. Open one window and seal
it with a loose cover of polyethylene sheeting. Turn on the heat
exchanger with both dampers fully open.
If the plastic bows or curves outward, the house has positive
pressure due to excessive intake airflow. Gradually adjust the damper
on the intake airflow until the plastic sheet is limp, curving neither
in nor out. At this point the two flows are balanced.
If the plastic curves inward, the house has negative pressure,
requiring that the damper on the exhaust side be adjusted to balance
the airflow.27



The exhaust air ducts should be located high on the wall, where the
most humid and stale air is present. (Cooking and showering give off
heat and humidity, which will rise.) According to heat exchanger
manufacturers, the fresh air ducts should also be located high on the
wall to allow the cooler fresh air to mix better, instead of staying
closer to the floor. Alternatively, if you have bathroom exhaust fans
already installed, you can route the exhaust ducts into an air chamber
leading to the heat exchanger.
When the clothes dryer is in operation, it will induce some imbalance
of the airflow between exhaust and intake air of the house since it is
adding to house air exhaust and not to air intake. It is possible to
reduce this imbalance by venting outside supply air directly to the
dryer or to make a small capacity heat exchanger core specifically for
the clothes dryer. The dryer fan system will drive both airflows and
no additional fans are needed. Such a heat exchanger core must be
provided with filters and frequently cleaned to remove collected
lint. (Putting such detail into the clothes dryer exhaust system
seems to be way too much work.)

Note: I used the “Superbooster” fan set-up (shown below) when I first
installed my home heat exchanger. By the time I needed replacement
fans, that company (Ancor Industries) was apparently out of business.
I was able to find a suitable replacement in local hardware stores.
(The Tjernlund company makes such duct boosters, WITHOUT the vibration-
absorbing foam rubber feature.)








Part Four
ADDITIONAL DATA
on Energy-Efficient Housing

Comparative Costs of Insulation

When trying to get a specific level of insulation, not all methods of
insulating cost the same.
A brief survey of insulation costs from building supply stores in the
Monterey, California, area resulted in the following lowest prices
(September 1987):

R-11 fiberglass costs $19.99 for a roll 23 inches wide by 70.5 feet
long.
R-19 fiberglass costs $18.99 for a roll 23 inches wide by 39.2 feet
long.
R-30 fiberglass costs $44.80 for a roll 23 inches wide by 58.3 feet
long.
R-14.4 (2 inches thick) isocyanurate board costs $19.25 for a 4 x 8
foot sheet.
R-28.8 (4 inches thick) isocyanurate board costs $31.78 for a 4 x 8
foot sheet.
Bag of rock wool costs $5.99 to cover 24 square feet of R-19.

These prices will result in the following net cost relationships:

% cost
Cost ($) per compared
Insulation Insulation Cost ($) per of square foot to R-11
type form square foot R-value of R-1 fiberglass

fiberglass roll/batt 0.1479 R-11 0.01345 100.0%
fiberglass roll/batt 0.2527 R-19 0.01330 98.9%
fiberglass roll/batt 0.401 R-30 0.01336 99.4%
rock wool loose fill 0.2496 R-19 0.01313 97.6%
isocyanurate rigid board 0.6015 R-14.4 0.0418 310.6%
isocyanurate rigid board 0.9931 R-28.8 0.0345 256.4%

(Calculation example R-11: 23" ÷ 12 inches per foot x 70.5 ft long =
135.12 sq ft of R-11 insulation for $19.99; $19.99 ÷ 135.12 sq ft =
$0.1479/sq ft of R-11. $0.1479 ÷ 11 (R-value) = $0.01345/sq ft of
R-1.)

Fiberglass and rock wool are only 34 to 45% of the cost of
isocyanurate. Although isocyanurate is 2 to 3 times as expensive as
fiberglass, it has special advantages: compactness, rigidity, a built-
in radiant barrier, and relative moisture resistance. The
isocyanurate board can be used where sheathing is sometimes used.
Isocyanurates (R-7.2 per inch) put the same amount of insulation value
in half the space of fiberglass.

Three examples of insulating a backward double wall, made to have
about R-40 in the curtain wall, will demonstrate the comparative
differences in cost between fiberglass and isocyanurate foam.



Example one uses 4 inches of Thermax sandwiched in between the inner
and outer wall and R-11 of fiberglass between the curtain wall studs.
The final insulative value is R-39.8; with about 11 inches wall
thickness. The cost is $1.14 per square foot of insulation for the
wall (Thermax at $0.9931 per square foot of the 4-inch thickness and
R-11 fiberglass at $0.1479 per square foot).
Example two uses R-30 fiberglass between the inner and outer wall and
R-11 fiberglass between the curtain wall studs. The final insulative
value is R-41, with about 16-inch wall thickness. The insulation cost
is $0.55 per square foot (R-30 fiberglass at $0.40 per square foot and
R-11 at $0.1479 per square foot).



Example three uses rockwool or fiberglass loose fill insulation to
fill the outer wall cavity. The final insulative value is R-41, with
about 16 inches wall thickness. The cost is about $0.54 per square
foot of R-41. If the loose fill insulation is lightly packed (and
continuous with the attic insulation), settling of the insulation will
not be a problem.17

Let us assume the following house size to calculate the total cost of
insulation to fill the curtain wall: single-story, 8-foot-high
ceilings, 28 x 44 feet in size. The curtain wall height will be
about 10 feet, considering 12 inches of attic insulation above the
wall and 12 inches of floor insulation below the wall. The area of
insulation is about 1,500 square feet (10 ft x 28 ft x 2 walls = 560
sq ft. 10 ft x 44 ft x 2 walls = 880 sq ft).
Example one will cost $1,710, example two will cost $825, and example
three will cost $810 in insulation costs alone. Examples 2 and 3 will
additionally need a radiant barrier, costing about $190 for 1,500
square feet of a basic radiant barrier (double-sided foil on Kraft
paper). The extra thickness of the curtain wall will add slight
increases in framing costs for examples 2 and 3. The cost difference
between fiberglass and isocyanurate is therefore not as large as the
insulation cost alone might indicate, although it is still more
expensive overall.
Trying to mount rigid foam boards as external insulative sheathing
can be a problem if the thickness of the foam is great. It would be
difficult to nail through 4 inches of rigid foam boards, then nail
some form of siding through the foam, still being able to find the
wall studs with the nails. It can be done more easily with 2 inches
of exterior foam; this method would not allow an insulation level much
over R-33, using 2 x 6 inch framing with 2-inch exterior foam.
External insulative sheathing can potentially induce internal wall
condensation, so it is probably safer to avoid that method when using
large amounts of insulation.
Loss of insulative ability in the aging of isocyanurates is another
factor to consider. New isocyanurates may be as high as R-9 per inch,
but aged isocyanurates will eventually fall well below R-7.2 per
inch. Twenty years later, the isocyanurate foam might have an
insulation level of R-5 per inch. Four inches of isocyanurate foam
might initially give an insulative value over R-30, but could
eventually fall to R-20. Isocyanurates release freon as they age,
adding damage to the ozone layer of the atmosphere. Typically, foam
products are manufactured using such chloro- and fluorocarbons. Some
foam products give off chloro- and fluorocarbons as they age, and are
also hazardous to the ozone layer. Fiberglass and rock wool are not
only fire-retardant and less expensive, but also environmentally safer
than foam insulations. However, mineral wool insulations will not
work in all applications. For example, exterior insulation of below
grade walls is best accomplished by a water-resistant foam insulation.
There are some commercially available insulations used for
retrofitting existing walls (Tripolymer®, Air-Krete®, and Blow-In
Blanket®). These insulations require installation with special
machinery by the appropriate company. Availability is currently
limited and installation is also costly (near or over $1.00 per square
foot of wall (as of 1989), when a 3.5-inch cavity must be filled).
The need for replacing the siding or increasing wall thickness is
avoided, but the final insulative value is limited at R-13 to R-17.
Vapor barrier problems will have to be resolved, or moisture damage to
the wall can occur. The insulation will be in close contact with
existing wiring within the walls, allowing potential fire hazards.
Less cost of insulation will be incurred by retrofitting exteriorly
($0.55 per square foot for examples two and three, above, for R-40
insulation levels). Of course, there are framing costs, costs for
replacing the siding, and additional labor costs. However,
retrofitting insulation exteriorly allows installation of a continuous
vapor barrier and high levels of insulation or superinsulation.


Costs of retrofitting insulation

Retrofitting insulation for an uninsulated building in a cold climate
can provide substantial energy savings over time. The investment of
time and materials provides financial payback if the initial cost is
not prohibitively high. Expensive changes on an old house in poor
shape may never be worth the time or financial investment.
The following size house is used to estimate retrofitting costs: 28
foot x 44 foot, single-story over a crawl space. All house
specifications are as listed in example 1 for winter heat loss
calculations.

Materials Needed for Insulation Retrofitting Approximate Cost (1988)

4,500 sq ft of 6 mil polyethylene vapor barrier for wall, ceiling, and
floor $216
Acoustical sealant or other caulk to seal vapor barrier 60
76 studs for curtain wall (2 foot on center, 2" x 4" x 8 ft) 152
60 studs (2" x 4" x 8 ft) for horizontal 2x4 members,
sole plates, ledger plates, and top plate (if needed) 120
2 sheets of ¼" plywood (4 x 8 foot) for plywood gussets 16
5 sheets of ¼" plywood (4 x 8 foot) to cover the bottom of the
curtain wall 40
76 joist hangers to support the curtain wall studs 38
1,480 sq ft of R-30 fiberglass for walls (no vapor barrier needed, or
put vapor
barrier up against the continuous polyethylene vapor barrier) 592
1,480 sq ft of R-11 fiberglass for walls 220
3,720 sq ft of R-19 fiberglass for attic (three layers thick) 960
2,480 sq ft of R-11 fiberglass for crawl space (two layers R-11 + 1
layer R-19, below) 370
1,240 sq ft of R-19 fiberglass for crawl space 320
Insulation support netting for supporting crawl space insulation 35
1,500 sq ft of perforated radiant barrier for walls 190
1,700 sq ft of radiant barrier for bottom of roof rafters 210
76 furring strips (1" x 2" x 8 ft) to make radiant barrier air space
on curtain wall 65
Tyvek infiltration barrier (150 feet x 9 feet) 150
40 sheets of 3/8" plywood (4 x 8 foot sheets) to be used as
replacement siding 500
Assorted sizes of nails and lag bolts for the job 80
Continuous soffit vents and ridge vents 100
Other miscellaneous tools, wood strips, supplies, paint, and/or wood
sealer 600
150 sq ft of double-pane windows to cover existing single-pane windows
900
Air-to-air heat exchanger with needed ducts (retail model) 900
Total $6,834

With an expected materials cost nearly $7,000, retrofitting is
hardly inexpensive. If the heating bill goes from $1,000 per year to
$90 per year, the job will be paid back in 8 years if you have free
labor. If you have to hire out the job, multiply the cost by at least
three.
Retrofitting insulation in a structurally sound house can be an
economically viable means of obtaining a superinsulated house. A do-
it-yourself person could potentially retrofit an existing home over a
period of years while living in the house. Insulation upgrades could
be added, as the money becomes available instead of saving for one
major retrofit project or trying to finance the purchase of a new
superinsulated house.

Assembling Superinsulated Walls

The text and diagrams in previous sections of this book explain the
concepts of superinsulation and the techniques needed to achieve
superinsulation. During construction, it is necessary to determine
the most efficient and cost-effective method to get the house
superinsulated. The text by Nisson and Dutt explains a few methods of
assembling superinsulated walls during construction.41 Their text
shows in diagrams and in a number of photographs the step-by-step
process used to construct superinsulated walls in new construction,
using the Canadian double wall technique.
McGrath2 explained to me the sequence of assembly during new
construction and one method to get the floor vapor barrier sealed to
the wall vapor barrier.
1. The plywood floor is cut into two sections and supported beneath by
blocking. The floor vapor barrier fits between the plywood cut. The
inner wall is framed on the floor. The vapor barrier is stapled on;
sheathing is applied over the vapor barrier.
2. A duplicate outer wall is framed over the top of the inner wall.
The outer wall is spaced by the desired separation of the two walls
(3.5", 5.5", 9", or as designed). Plywood plates (¾ " thick) are
attached along the top and bottom of the wall to maintain the
separation of the two parallel walls. The insulation may be installed
in the outer wall cavities (with or without siding) at this time.
3. The double wall is tilted into place. The vapor barrier is then
sealed to the floor. The ceiling joists (or second floor joists) are
then added, the vapor barrier is sealed in place, and construction
continues to complete the exterior of the building. The inner wall
ends before the corner of the building to attach the vapor barrier to
the adjoining wall.
McGrath feels that making the inner wall structural and later adding a
curtain wall allows better vapor barrier connections (see the diagrams
on pages 68 and 71).



The three-step method illustrated above achieves a continuous vapor
barrier at the floor, although it requires extra work for the blocking
beneath the inner wall. The Canadian double wall technique uses
thinner (3/8") plywood plates, shows the vapor barrier wrapped around
the floor joist header, and has the vapor barrier covered exteriorly
by rigid insulation. Alternative methods of assembly are possible and
some of these techniques are described and evaluated in the text by
Nisson and Dutt.41

Vapor Permeability of Materials

Vapor flow through various materials is measured in perms. A low
perm rating will block the passage of water vapor, a high perm will
let vapor through readily. If a material has a perm of 1.0, it will
allow 1 grain of water to pass through a 1 square foot area in 1 hour
when there is a 1-inch of mercury vapor pressure difference between
the two sides of the material. One grain of water is about 1/7000 of a
pound.2
Since warm air holds more moisture than cold air, the warm side will
have the higher vapor pressure and water vapor will try to migrate to
the cold side. The better the vapor barrier, the less vapor that will
actually get through the wall. The moisture that does manage to get
through the vapor barrier will have to escape through the cold side of
the wall. If the outside wall also has a low perm rating, the
moisture will tend to get trapped in the wall. The outer wall should
have at least 3 times the permeability of the inner vapor barrier, or
moisture will tend to get trapped in the wall.2

Perm ratings of various materials

Sheetrock, ½” 20.0 Glidden "insulaid" paint 0.6
Exterior plywood, ¼” 0.7 Enamel paint on plaster 0.5 to 1.5
Interior plywood, ¼” 1.9 Hardboard, 1/8" 11.0 to 5.0
Glass (windowpane) 0.0 15 pound asphalt felt 1.0 to 5.6
Fiberglass insulation, 1" 116. 8" concrete block (hollow) 2.4
Aluminum foil, 0.35 mil 0.05 Concrete, 1" thick 3.2
Aluminum foil, 1 mil 0.0 Brick, 4" 0.8
Polyethylene, 4 mil 0.08 Glazed masonry tile 0.12
Polyethylene, 6 mil 0.06 Beadboard, 1" 2.0 to 5.8
Polyethylene, 10 mil 0.03 Styrofoam, 1" 1.2
Thermoply sheathing, 1/8" 0.6 Urethane board, 1" 0.4 to1.6
Tyvek ® housewrap 94. Insulation back-up paper 0.04 to 4.2
Roifoil (radiant barrier) 0.5 Foil-Ray® radiant barriers 0.02

Table derived from The Superinsulated House, by Ed McGrath.

The most widely used vapor barrier is 6 mil polyethylene (6/1000
inch thick). To make the barrier function effectively, seal the vapor
barrier at all seams and points where the membrane is crossed
(electrical boxes, wires, attic openings, and the like).

How much water vapor can get through a vapor barrier?

Even a well-sealed 6 mil polyethylene vapor barrier will have nail
holes and small tears, increasing the overall perm rating to 0.10 or
more. If the vapor barrier or its joints deteriorate with age, there
will be condensation problems in later years. TenoArm film is a 8 mil
vapor barrier material claimed to be more resistant to aging than
polyethylene. 3 (See product listings after the references.)

This formula describes water vapor transmission:
WVT = A x T x ∆P x Perms, or :
Water Vapor Transmission = Area x Time x ∆Vapor Pressure x Perms

Area = Square feet area of outside of building.
Time = Number of hours measured.
∆P = Difference of inside and outside vapor pressures.
Perms = Overall perm rating of the vapor barrier.

To demonstrate the use of the above formula, three examples will be
given using the same house dimensions: 28 feet x 44 feet x 8 feet high
(3,616 square feet outer surface area for walls, floor, and ceiling).
The vapor barrier transmission is measured for the month of January
(744 hours in the month).

Example A . This example is a house with a nearly perfect vapor
barrier, with an overall perm of 0.1. Inside relative humidity is
35%, outside relative humidity 65%, inside temperature 70°F and
outside temperature +10°F for January (northern United States).
From the table below, 70°F is 0.739, x 0.35 (RH) = 0.258.
Outside: +10°F is 0.0629, x 0.65 (RH) = 0.041. The difference
between the two values is 0.217 inches of mercury vapor pressure.
WVT = 3,616 x 744 x 0.217 x 0.1 = 58,380 grains of water, or 8.34
pounds of water. Which is about 1 gallon of water for the month of
January.

Example B. The same size house with no vapor barrier film, yet the
wallboard is covered with a vapor barrier paint, having an overall
perm of 1.0 . Since the air in the house gets dry at times, the
occupants run a humidifier intermittently to keep the RH up to 35%.
WVT = 3,616 x 744 x 0.217 x 1.0 = 583,800 grains of water, or 83.4
pounds. This is 10 gallons of water. With a 4-month heating season,
40 gallons of water can escape through the walls, floor, and
ceiling.

Example C . There is no vapor barrier, and the walls and ceilings are
painted with a flat wall paint, with a perm of 10.0 (for 2,384 square
feet). The floor makes a fair vapor barrier due to the layers of
flooring and tile, with an overall perm of 1.0 (for 1,232 square
feet). The air gets very dry, but the occupants run a humidifier most
of the time to keep the air "moist." Still the RH stays at only 15%,
since there is much continuous loss of vapor.
WVTfloor = 1,232 x 744 x 0.069 x 1.0 = 63,246 grains of water, or
9.035 pounds of water (slightly more than a gallon of water).
WVTwalls, ceilings = 2,384 x 744 x 0.069 x 10.0 = 1,223,850 grains
of water, or 174 pounds (about 21 gallons of water). With a 4-month
heating season, this could amount to over 80 gallons of water that
escapes into the wall and ceiling area. Since about half of the
surface area is ceiling, expect half of the water to get into the
attic. If the attic is not well ventilated, the moisture will
condense on the cold side of the attic (making ice balls on the nails
in the roof or freezing in the attic insulation). This ice will melt
early in spring and may run through the ceiling. If it can't drip
through, the ceiling could be seriously damaged. This same moisture
will eventually rot the structural members of walls as well as causing
peeling paint or rotted siding. A good vapor barrier is very
important to protect the walls and ceilings.

A house with a good vapor barrier will not need to add moisture in
winter. The problem will be getting rid of water vapor in the house.
Normal activities of the home (washing, showering, cooking, and
breathing) add significant amounts of water vapor to the home. An
air-to-air heat exchanger, replacing air continuously at 70 cfm from a
house with a relative humidity of 30%, will remove about 5 gallons (20
liters) of water a day under winter conditions.26
A house without a vapor barrier will tend to have dry air during the
heating season. The moisture inside is greater than outside, so the
vapor will try to get out wherever it can by going through walls,
floors, and ceilings. If the occupants run a humidifier, this will
add to the supply of moisture in the air, and even more moisture will
get into the walls and attic. If special measures are not made to
remove the moisture, over time there will be rotting of siding and
studs, with potential damage to the ceiling when the ice melts in
spring.
While a humidifier makes the occupants more comfortable in winter, it
increases vapor damage to the house. The solution is a vapor barrier,
either vapor barrier paint or some form of vapor barrier installed if
adding insulation. If insulation is added without putting in a good
vapor barrier, there can be much more rapid damage to the house.
Since the moisture will get trapped in the insulation, it will cause
rot of the wall over the years.16
The above calculations on water vapor transmission are based on
passive diffusion of vapor through walls, ceilings, floors, and vapor
barriers. In actuality, most vapor condensation is due to movement of
air through the joints of walls, floors, ceilings, through other
breaks in these surfaces, and through plumbing and electrical wiring
pathways. Due to the chimney effect, air from within the house will
rise into the attic through any available opening; this significantly
increases heat loss and eventual water vapor condensation in the
attic. Retrofitting a continuous attic vapor barrier blocks airflow
into the attic and prevents much subsequent heat loss and vapor
condensation. Retrofitting a continuous attic vapor barrier has
significant value, even though it is a laborious and time-consuming
process. Plan to do attic retrofit work during rather cool weather to
avoid hot attic temperatures.

Vapor pressures for saturated air

Degrees F. Inches mercury Degrees F. Inches mercury

-60 0.0010 +20 0.1028
-50 0.0020 +30 0.1645
-40 0.0039 +40 0.2478
-30 0.0070 +50 0.3626
-20 0.0126 +60 0.5218
-10 0.0220 +70 0.7392
0 0.0377 +80 1.0320
+10 0.0629 +90 1.4220
+100 1.9334

Table derived from The Superinsulated House, by Ed McGrath.


Selecting the Appropriate Overhang
for South Windows

South windows are useful in obtaining passive solar heating. With
south-facing windows, the proper overhang allows the winter sun to
enter but blocks the summer sun. A small overhang (18 inches) is
sufficient for most southern locations of the United States.
Progressively longer overhangs would be needed to give the same summer
shading in more northern locations.
Procedure. Use the "overhang lengths" table to design the proper
sized overhang.
1. Determine the amount of shading needed for summer, depending on the
climate. Long hot summers will need up to 6 months of complete
shading; cool summers in the north may not need complete summer
shading.
2. Determine the amount of winter exposure needed. Brief winters in
the south might not need complete window exposure; long winters in the
north may need over four months of complete window exposure.
3. Determine the best compromise between the two selections.



Examples. Miami Beach, Florida (26° north latitude), has a minimal
heating demand of 200 degree-days. Minimal solar gain is needed, but
a long shading period is advised. An overhang length of 18 to 34
inches is reasonable.
Harrisburg, Pennsylvania (40° north latitude), has cold winters
(5,251 degree-days) and hot summers. There should be good window
exposure in winter and good shading in summer. A 28-inch overhang
will provide 2 months of full exposure in winter, and two months of
complete shading in summer.





Prince George, British Columbia, Canada (54°-north latitude), has cold
winters (9,755 degree-days) and mild summers. An overhang length of
36 to 46 inches provides good solar gain in winter and reasonable
shading in summer.

Constant overhang method. Using standard framing (about 16 inches of
framing above the window) and a 5-foot window height, an overhang
length of 28 inches for all south-facing windows will provide
reasonable shading regardless of the climate. In the overhang lengths
table, a 28-inch overhang is shown to provide progressively longer
summer shading for hot southern locations (25° to 35° north latitude)
and progressively longer winter solar exposure for cold climates (45°
to 55° north latitude).
For 5-foot-high windows, the correct overhang can be determined by
use of the standard framing method, the nonstandard framing method,
the constant overhang method, or the values described in the overhang
lengths table. For other window heights, the proper overhang
dimensions can be determined by calculation.

Calculation method for overhang determination



Situation. A builder plans to use 8-foot-high windows on a south-
facing sunspace. The geographic location is 45° north latitude. The
plan is to have the windows completely exposed from 21 November to 21
January. Also, the windows are to be completely shaded from 21 May to
21 July.
Values interpolated from the Solar Position chart
Noon sun height is about 65° on 21 May and 21 July.
Noon sun height is about 25° on 21 November and 21 January.
Values from standard trigonometry tables
Tangent 65° = 2.145; Tangent 25° = 0.466



Conclusion. Overhang length = 4.75 feet Height above window =
2.25 feet


Design Temperatures for Heating
and Cooling for Selected Locations

Winter design temperatures represent outside temperatures that are
equaled or exceeded 99% of the hours in December through February.
Heating degree-days is a measure of coldness. The number of degree-
days in a calendar day is calculated as follows: subtract the average
of the high and low temperatures of the day from 65°. As an example,
if the average high for a specific day is 60° and the average low for
that day is 20°, there are 25 degree-days on that day. (60° + 20° =
80°; 80° ÷ 2 = 40°; 40° is the average temperature for that day;
65° - 40° = 25 degree-days for that day.) All of the degree-days for
a heating season are added to determine the heating degree-days for a
year. Summer design temperatures represent outside temperatures that
will be equaled or exceeded 1% of the hours in June through
September. The level of summer heat is compared to an inside
temperature of 75°. The heating degree-days and winter design
temperatures can be contrasted to the hours of summer cooling and
summer design temperatures to get a relative indication for the total
climate demands on a building. In another text, "cooling degree-days"
are quantified for selected cities in North America.41 In locations
where the heating degree-days are minimal, the cooling hours and
summer temperatures may be more significant. Below are a few
excerpts from: Insulation Manual, published by the NAHB Research
Foundation.

Winter Degree Summer Hours of
design -days design summer
State: City temp. (°F) (heating) temp. (°F) cooling

Alabama: Birmingham +17 2,710 96 1,430
Alaska: Fairbanks -51 14,500 82 190
Juneau -4 9,080 74 70
Arizona: Phoenix +31 1,680 109 2,010
Arkansas: Little Rock +15 3,170 99 1,440
California: Los Angeles +41 1,960 83 530
San Diego +42 1,500 86 620
San Francisco +35 3,040 82 180
Colorado: Denver -5 6,283 93 750
Connecticut: Hartford +3 6,170 91 630
Florida: Jacksonville +29 1,230 96 2,040
Miami Beach +44 200 91 3,250
Georgia: Atlanta +17 2,990 94 1,320
Hawaii: Honolulu +62 0 87 3,950
Idaho: Boise +3 5,830 96 680
Illinois: Cairo +4 3,820 97 1,300
Chicago -5 6,160 94 790
Indiana: Evansville +4 4,500 95 1,160
Indianapolis -2 5,630 92 870
Iowa: Des Moines -7 6,610 94 810
Kansas: Topeka 0 5,210 99 1,030
Kentucky: Lexington +3 4,760 93 1,000
Louisiana: New Orleans +29 1,400 93 2,090



Winter Degree Summer Hours of
design -days design summer
State: City temp. (°F) (heating) temp. (°F) cooling

Maine: Portland -6 7,570 87 390
Maryland: Baltimore +10 4,680 94 970
Massachusetts: Boston +6 5,630 91 660
Michigan: Detroit +3 6,290 91 710
Minnesota: Minneapolis -16 8,250 92 640
Mississippi: Jackson +21 2,260 97 1,620
Missouri: Kansas City +2 4,750 99 1,180
St. Louis +2 4,900 97 1,140
Montana: Missoula -13 8,000 92 440
Nebraska: Omaha -8 6,290 94 860
Nevada: Reno +5 6,150 95 700
New Hampshire: Manchester -8 7,100 91 610
New Jersey: Newark +10 4,900 94 840
New Mexico: Albuquerque +12 4,350 96 1,120
New York: Buffalo +2 6,960 88 610
New York +12 4,880 90 850
North Carolina: Fayetteville +17 3,080 95 1,280
North Dakota: Grand Forks -26 9,930 91 500
Ohio: Cincinnati +1 4,830 92 970
Cleveland +1 6,200 91 740
Columbus 0 5,670 92 890
Oklahoma: Oklahoma City +9 3,700 100 1,240
Oregon: Portland +17 4,700 89 340
Pennsylvania: Philadelphia +9 5,180 93 910
Pittsburgh +1 5,950 89 720
Puerto Rico: San Juan +67 0 89 4,350
Rhode Island: Providence +5 5,950 89 600
South Carolina: Columbia +20 2,520 97 1,460
South Dakota: Rapid City -11 7,370 95 660
Tennessee: Memphis +13 3,210 98 1,430
Nashville +9 3,610 97 1,210
Texas: Dallas +18 2,320 102 1,820
El Paso +20 2,680 100 1,620
Houston +27 1,410 96 2,060
San Antonio +25 1,560 99 1,980
Utah: Salt Lake City +3 5,990 97 820
Vermont: Burlington -12 8,030 88 520
Virginia: Richmond +14 3,910 95 1,090
Washington: Seattle +21 5,190 84 200
Wisconsin: Milwaukee -8 7,470 90 570
Wyoming: Sheridan -14 7,740 94 600


Percentage of Sunshine for Selected Locations

The actual solar gain a window or solar collector receives per
month is determined by several factors: 1) solar insolation (solar
heat gain per day). 2) Number of days in the month. 3) Percent actual
sunshine. 4) Deviation from true south. 5) Area of the window, less
any shading factor of the window (framing, extra panes, inside
curtains), and 6) Sky clarity factor, 1.0 (if clear) to 0.85 (hazy).
Example: Solar gain for the month of January in Kansas City, Missouri
(40° N. latitude), for a window 30 square feet in net size, facing 30°
from true south can be calculated:
1415 BTU/square foot/day x 31 days x 0.55 clear days x 0.90 deviation
x 30 sq ft
This gives about 651,400 BTUs solar gain for the month of January.

Location Mean percent Sunshine Location Mean percent Sunshine
Winter Summer Winter Summer

Alabama: Birmingham 45 65 North Carolina: Asheville 50 60
Alaska: Fairbanks 37 44 Raleigh 53 63
Juneau 27 31 North Dakota: Bismarck 53 68
Arizona: Phoenix 79 87 Ohio: Cincinnati 42 70
Arkansas: Little Rock 48 72 Cleveland 30 69
California: Eureka 41 51 Oklahoma: Oklahoma City 58 77
Fresno 52 96 Oregon: Portland 28 63
Los Angeles 70 76 Roseburg 25 72
San Francisco 55 68 Pennsylvania: Harrisburg 46 65
Colorado: Denver 66 68 Philadelphia 50 62
Connecticut: Hartford 48 61 Pittsburgh 34 62
Florida: Jacksonville 57 63 South Carolina: Charleston 58 67
Miami Beach 68 65 Columbia 54 65
Georgia: Atlanta 49 64 South Dakota: Rapid City 58 71
Idaho: Boise 42 83 Tennessee: Knoxville 44 63
Illinois: Chicago 45 71 Memphis 47 74
Indiana: Indianapolis 42 71 Nashville 44 69
Iowa: Des Moines 53 70 Texas: Austin 48 76
Kentucky: Louisville 42 70 Brownsville 46 76
Louisiana: New Orleans 48 61 El Paso 75 81
Massachusetts: Boston 50 63 San Antonio 49 73
Michigan: Detroit 35 67 Utah: Salt Lake City 50 81
Minnesota: Duluth 47 64 Vermont: Burlington 34 60
Minneapolis 48 68 Virginia: Norfolk 53 66
Mississippi: Vicksburg 47 71 Richmond 51 64
Missouri: Kansas City 55 73 Washington: Seattle 28 55
St. Louis 47 71 Spokane 30 76
Montana: Helena 48 71 West Virginia: Elkins 34 55
Nevada: Las Vegas 76 87 Parkersburg 32 61
New Hampshire: Concord 48 57 Wisconsin: Green Bay 45 66
New Jersey: Atlantic City 53 66 Madison 44 67
New Mexico: Albuquerque 71 78 Milwaukee 44 68
New York: Albany 44 62 Wyoming: Cheyenne 65 69
New York City 52 65 Sheridan 56 72

This table is derived from: Designing & Building a Solar House, by
Donald Watson. The sunshine values
are averaged for three months of winter and summer: winter –
December, January, and February, and
summer – June, July, and August).

Groundwater Temperatures in Shallow Wells

Groundwater is available in most parts of the United States. The
temperature of groundwater remains moderate and relatively stable year-
round. Groundwater could be used as a source of heating and cooling
for heat pumps.
A number of states regulate the withdrawal, use, and discharge of
ground water. Local authorities should be consulted to determine the
current regional regulations. Also, the case can be made that to use
groundwater solely as a heat exchange medium is ecologically wasteful.
It is not necessary that water utilized in a heat pump be used once
and discharged. Water can be re-circulated between a sealed storage
well and the heat pump. When the water is in the well, its
temperature is allowed to equilibrate with the surrounding water and
earth. In this way, heat is extracted from or deposited in the ground
without using up valuable water.
The figure below demonstrates the mean temperatures (°F) of
groundwater in shallow wells (30 to 60 feet deep) in the United
States. 38

Groundwater temperatures in shallow wells


A text by McConnel shows similar temperature data, listing in table
format the expected "Ground Temperatures below the Frost Line." 30
The values listed by McConnel, show a similar temperature distribution
throughout the country. The temperature values in the above map
indicate potential thermal demands on sections of buildings below the
frost line. As well as providing an indication of the feasibility of
using a geo-thermal heat pump, these temperature values can also
indicate the thermal effectiveness of "earth-tubes."

Magnetic Variations from True North

A magnetic compass helps find the approximate direction, but true
north does not coincide with magnetic north throughout the country.
Solar orientation should be corrected to the true south direction to
obtain the best solar gain. Due to the molten nature of the earth's
metallic core, the magnetic poles continue to shift somewhat each
year.



Alternative methods: 1) North can be determined by the position of the
North Star, accurate within a few degrees. 2) Solar noon is midway
between sunrise and sunset. Local newspapers may list the time of
sunrise, sunset, or solar noon; the shadows cast at solar noon will
help determine true south. 3) Daytime shadows: a) Drive a 5-foot
stake vertically in the ground and mark the end of the stake's shadow
at one time during the morning. b) Using a string tied to the base of
the stake and to a pointed stick, draw an arc through the end of the
shadow to the other side of the stake. c) Mark where the end of the
afternoon shadow intersects the arc. d) Connect the ends of the
shadows with a line. e) Bisect the line; this midway point is
directly north of the stake casting the shadow.

Winter Solar Gain and Deviation from South



Solar Position
The table below lists the sun height (altitude in southern sky) at
noon on the 21st of the month for major latitudes. Also shown is the
sun's azimuth at sunrise and sunset; this is the number of degrees
away from south, where 90° is directly east or west.

(Above table derived from Designing & Building a Solar House, by
Donald Watson)
The solar position at noon can be interpolated for latitudes not
listed on the above chart. The approximate position of the sun
compared to the equator of the earth is shown on the chart below. The
listed values are for the 21st of each month.


In the Southern Hemisphere, the opposite window orientation is needed,
meaning face windows NORTH to maximize winter solar gain. Another way
of putting it: “Face windows toward the equator to maximize winter
solar gain.” (And at the equator there’s no winter to worry about.)

Clear-day Solar Heat Gain for Double - glazed Windows (BTU/sq ft/
day)









Values listed account for 26% reflection/absorption from double-
glazing. Solar gain tables are
derived from The Passive Solar Energy Book and Solar Energy:
Fundamentals in Building Design.

Moisture Condensation
within Sealed Panes of Glass

Double-glazed windows usually are manufactured with two panes of
glass sealed in a frame separated by an insulating air space. There
is no ventilation between the panes of glass. However, the
manufacturer usually installs desiccant crystals in the spacer bars
holding the panes of glass apart. The desiccant will absorb moisture
that gets around the inside pane. Under high inside humidity
conditions, especially if the inside pane develops a poor seal,
condensation eventually may occur between the panes. Usually these
windows must then be replaced. However, with some windows this
problem can be resolved by venting the space between the panes to the
outdoors. A hole must be drilled into the approximately 3/8-inch
space between the panes and then intersect this hole by drilling
another hole from the outside. Careful measurements must be made in
advance to avoid striking the glass panes. Only a small drill hole is
needed. Small ventilation passageways allow the condensed moisture
eventually to escape to the outside. Typically the spacer bars
separating the panes have desiccant crystals. If such crystals are
released between the panes, it could cause a bigger mess. First drill
the hole into the frame, to reach the space between the panes. Then
it should be possible to insert a “tension pin” (the same size as the
drill bit – tension pins are sold by some hardware stores) into that
opening to block the crystals from getting between the panes. (Leave
the tension pin in position to keep crystals from falling between the
panes; see the diagram on the next page for how to position the vent
holes.) Continue with the second hole to vent the space between the
panes to the outside. If you are unsuccessful, you may still have to
replace the window.
Related comments. Some energy consultants in the southern United
States recommend that a vapor barrier be placed both on the interior
and exterior of walls in hot, humid climates. However, observing the
above-mentioned vented windows in cold winters and long hot, humid
summers (near Savannah, Georgia), the condensation did not return even
in summer. This suggests that such "double vapor barriers" for walls
may also be unnecessary in some hot, humid climates.









Other Energy-Saving Ideas

Water-saving showerheads

There are many water-saving showerheads on the market that claim to
use small amounts of water. The objective is to get a conservative
flow rate without lessening the quality of the shower. A good feature
is a small shutoff valve in the showerhead that stops the water flow
while you lather with soap. The shutoff valve should actually keep
the water flowing at a slow rate to reduce mixing of the hot and cold
water within the pipes. A well-designed water-saving showerhead will
reduce hot water utility costs, since there is a significantly
decreased water flow rate during the course of the shower. One model,
(SaverShower, model SS-2, by Whedon Products, Inc., 20 Hurlbut Street,
West Hartford, CT 06110) has water-saving features with a durable
brass construction. Up to $200 savings a year on fuel and water costs
is claimed for an average-sized family using this showerhead compared
to a conventional shower head. This product received high ratings as
an aerating low-flow shower head when evaluated by Consumer Reports in
June 1985. SaverShower is sold by True Value and Ace Hardware stores
(as of 1989). Numerous other brands of water-saving shower heads are
available at hardware stores and some department stores.

Reducing water heating costs

An energy-efficient house can have a higher water-heating bill than
the space heating bill. Use of conservation techniques can reduce the
water-heating bill.

1. Use brief showers instead of baths.
2. Fix leaky faucets. A dripping hot water faucet not only wastes
cold water but heated water as well. Water costs can really add up
over time; one drop every two seconds will waste over 170 gallons per
year.
3. Use cold water for laundry whenever possible.
4. Add insulation to the hot water tank and to the water lines leading
out of the tank and for about three feet before coming into the tank.
However, insulating a water heater can cause problems. With gas water
heaters, the insulation should not cover the combustion chamber of the
tank and should avoid the exhaust flue, (unless the insulation is
resistant to combustion). For electric water heaters, do not insulate
the part of the tank near the heating elements. The excess heat
trapped can melt the electrical insulation and burn out the heating
element. Some new models of water heaters are improved so as not to
require added insulation except for use on the pipes.
5. Insulate hot water lines en route to points of usage. In new
construction, try to keep a short distance from the hot water tank to
the points of usage.
6. Set the water heater temperature no higher than 120° F. 24


Two-tank system. Water entering a home can be significantly colder
than temperatures inside the house. In some climates, water enters
the house at 45° F. Water can be preheated before reaching the hot
water tank by use of an uninsulated water storage tank put in the
water line before the water heater. If the room temperature is 70°,
part of the water heating can be taken care of by house heat as the
water has time to reach room temperature. Although this method takes
heat from the house, an energy efficient house has excess heat for
eight or more months a year. The water is then preheated from 45° to
70° (about 25°), leaving an additional 50° to be heated by the water
heater.24
If a sunspace is used, excess heat from the sunspace can be vented to
the house to help with the space heating needs. Alternatively, excess
heat from the sunspace could be first vented into a chamber containing
small sealed water bottles for thermal storage. If the two-tank
method of water heating is used, the pre-heating tank could be
positioned to receive heat from the sunspace, to further pre-heat the
water before reaching the water heater. This might pre-heat the water
to perhaps 85° F.
Solar panel designs. Solar hot water heaters are available for
domestic use. Some do-it-yourself plans are available for solar water
heaters. There is higher cost and complexity to solar systems as well
as limitations, since solar heat is not always sufficient for the
demand. Furthermore, protection from freezing must be designed into
such systems for many geographic locations. One heat pipe type solar
water heater reportedly eliminates any freezing problems. 34
Another possibility for solar water preheating is the Sunflare 2000.
The solar water pre-heater has a built-in reflector that focuses
sunlight on the black surface of the water tank. This device is
intended for outdoor use in moderate and tropical climates. It could
be suitable year-round in colder climates if used in a sunspace
providing direct solar exposure of the unit (Practical Homeowner,
December 1987, p. 67).

Water-saving toilets

Most conventional toilets (as of the late 1980s) used 3.5 gallons of
water per flush and were termed water-saving toilets because they use
less than the older 5+ gallon toilets.
Newer water-saving toilets use typically 1.6 gallons per flush.
Toilets using 1.6 gallons work essentially the same as conventional
toilets. However, they are engineered to require less water to
complete a thorough flushing of the bowl. These toilets supply the
proper amount of water to initiate the siphon action that begins the
flush, water to rinse the bowl, and just enough water to refill the
bowl to its proper position. The 1.6-gallon water-saving toilets will
often clear the bowl more effectively than some 3.5-gallon toilets.
The new water-saving toilets are better designed to flush down the
drain, whereas some conventional toilets waste much water swirling
around the bowl. Even when an additional flush might be needed, the
new water-saving toilets refill quickly since there is much less water
to replace. It might appear that such a small volume of water cannot
move the waste material adequately through the sewer lines even if it
removes it from the bowl. However, the additional water running
through the same sewer lines for hand washing and bathing will serve
to move the waste material through the sewer pipes.
There are many versions of ultra low-flush toilets; a few brands are:
Superinse, Ultra-One/G, Cashsaver MX, Microflush, and Cascade.
Superinse and Ultra-One/G look and work similar to earlier made 3.5
gallon toilets, except for their low water usage.

The Ifö Cascade, a Scandinavian design, is slightly different from
conventional toilets in that the flush lever is on the top of the
tank. (Since the top of the tank has the flush lever and is dome-
shaped, it cannot be used as a shelf for assorted bathroom supplies.)
The Cashsaver MX, also marketed as Flushmate, has a flat top to the
tank, with the flush button in the center of the tank top. The
Cashsaver MX uses an air-tight chamber within the tank. The high-
pressure water from the supply line forces water into the chamber.
When flushed, the high-pressure water accomplishes the flush. The
compression tank apparently can be retrofitted into some existing
toilets. The company claims the most effective cleansing of the bowl
and the best drainline carry of any toilet on the market.
The low-volume Microflush has a flapper valve in the toilet that
opens during the flush. The waste material moves through the opening,
the flapper valve closes, and a compressed air system forces the waste
material through the sewer pipes.35

Water-saving toilets

Allegro (1.6 gal.): Mansfield Plumbing Products, 150 First St.,
Perrysville, OH 44864
Aqualine (1.5 gal.): U.S. Brass, Bobby Rogers, 901 10th St., P.O.
Box 37, Plano, TX 75074
Atlas (1.5 gal.): Universal Rundle, 303 North St., Newcastle, PA
16103
CraneMiser (1.6 gal.): Crane Plumbing, 1235 Hartrey St., Evanston,
IL 60202
Cashsaver MX (1.4 gal.): Water Control International, Inc.,
2820-224 West Maple Road, Troy, MI 48084
Flush-o-matic (0.25 gal. -- mechanical trap seal): Sanitation
Equipment, 35 Citron Court, Concord, Ontario, Canada L4K257
Hydro Miser (1.6 gal.): Peerless Pottery, P.O. Box 5581,
Evansville, IN 47716
Ifö Cascade (1.0 to 1.5 gal.): Ifö Water Management Products, 2882
Love Creek Road, Avery, CA 95224
Madera Aquameter (1.6 gal.): American Standard, P.O. Box 6820,
Piscataway, NJ 08855-6820
Microflush or Toto (Microflush: 0.5 gal -- an air compressor and air
storage tank are also needed; or Toto: a 1.6 gal. gravity-fed flush):
Microphor, Inc., 452 East Hill Road, P.O. Box 1460, Willits, CA
95490
Pearl (1 cup water -- mechanical chemical foam flush): Water
Conservation Systems, Damonmill Square, Concord, MA 01742
Santa Fe (1.6 gal, adjusts to 1.9 gal.): Artesian Plumbing Products,
201 E. 5th St., Mansfield, OH 44901
Superinse (1.1 gal.): Thetford Systems, Inc., Ann Arbor, MI 48106
Turboflush (1.6 gal.): Briggs, 4350 W. Cypress St., Suite 800, Tampa,
FL 33607
Ultra Flush (1.6 gal.): Gerber Plumbing Fixtures Corp., 4656 W. Touhy
Ave., Chicago, IL 60646
Ultra-One/G (1.4 gal.): Eljer, Three Gateway Center, Pittsburgh, PA
15222
Veneto (1.5 gal.): Parcher, Inc. 13-160 Merchandise Mart, Chicago,
IL 60654
Wellworth Lite (1.5 gal.): Kohler Company, Kohler, WI 53044

Many of the above addresses were extracted from: Kourik, Robert,
Toilets: The Low-Flush/No-Flush Story, Jan/Feb 1990, Garbage
magazine, P.O. Box 56519, Boulder, CO 80322-6519.

I have heard of consumers unhappy with the requirement to have low-
flush toilets in new construction. Changes in Federal Law mandated
the use of low-flush toilets. However, the law did not mandate good
performance in low-flush toilets. Before installing such a toilet, it
can be a good idea to consult a reference source, such as Consumer
Reports magazine, to determine a suitable brand.

Additional Commentary on Toilets. In 1988 I moved into a newly built
house, which had 3.5-gallon toilets installed. Having just researched
various types of ultra low-flush toilets, I was disappointed in having
the 3.5 gallon versions. I eventually replaced all three of these
toilets with ultra low-flush (1.6-gallon) versions, for various
reasons. I selected a brand based on performance cited in Consumer
Reports magazine (Eljer Patriot). Over time, I found that indeed
there are conditions where the low-flush toilets do sometimes “back-
up” more easily during flushes. However, the consequences are not as
severe. With the older 5+ gallons per flush toilets, if they didn’t
flush down the drain on the first flush, they overflowed onto the
floor. With the 3.5-gallon toilets, sometimes it didn’t flush fully
on the first flush. If it was actually backed-up, and then you
flushed it again, it would typically overflow onto the floor. With
the ultra low-flush versions, with two flushes on a backed up toilet,
it does not usually overflow. Then you realize you need a plunger,
but that “cleanup” is relatively easy.
In 2005, I moved again, just several miles away to another house,
having 3 toilets of the 3.5-gallon versions. In 2007, I replaced all
three toilets with the Eljer Titan version. This brand and version
appears to be the most efficient performance that can ever be hoped
for, and was top rated at this time by Consumer Reports. The list
value for the toilet was about $400, but was carried in the basic
white color by the local Lowe’s store, for about $260 total for the
base + tank assemblies. This version has an elongate bowl, higher
toilet (seat) height (16.5” instead of the usual 14”), which makes it
a much more comfortable seat to use, especially for tall people. Not
only that, but the toilet seems unable to be clogged or to overflow.
It still uses 1.6 gallons per flush, yet it has a more powerful
flush. In over a year of use, none of the 3 toilets have once showed
any sign of back up or failure to flush.

References

1. Wolfe, Ralph, and Peter Clegg. Home Energy for the Eighties.
1979. 264 pages. Garden Way Publishing, Pownal, Vermont 05261. The
copyright for this text is held by Ralph Wolfe and Peter Clegg. This
text is out of print, as of 1990.
2. McGrath, Ed. The Superinsulated House. 1981. 103 pages. That
New Publishing Company, 1525 Eielson Street, Fairbanks, Alaska
99701. The price was $11.95 in April 1987. As of 1988 this book was
out of print. The Superinsulated House contains a wealth of data on
how to build energy-efficient homes in the coldest of climates.
3. Flower, Robert G. "1987's Greatest Hits," December 1987, Practical
Homeowner Magazine, pages 18-22 give data on energy-saving
products. Copies of Practical Homeowner cited in this and other
references may be requested from Practical Homeowner, 27 Unquowa Road,
Fairfield, CT 06430, (203) 259-9877.
4. Flower, Robert G. "The Super-Cool House," August 1987, Practical
Homeowner Magazine, pp. 66 - 69.
5. Flower, Robert G. "The Tighter Wall," October 1987, Practical
Homeowner Magazine, pp. 90 - 94.
6. New House Planning & Idea Book. 1983. 91 pages. Alberta
Agriculture, Home and Community Design Branch, Edmonton, Alberta
(Canada). United States edition published by: Brick House Publishing
Co, Inc., P.O. Box 134, Acton, MA 01720.
7. Langdon, William K. Movable Insulation. 1980. 379 pages.
Rodale Press, Inc., 33 E. Minor Street, Emmaus, PA 18049. This
book contains much data on insulating windows by various types of
shutters, shades, and quilts.
8. The Miracle of Rigid Vinyl. This informational brochure was
prepared by LEA Products Inc., Manufacturers of Vinyl Windows, 2642
Roselle Street, Jacksonville, FL 32204. Data in this brochure were
derived from Heating, Ventilation and Air Conditioning Guide,
American Society of Testing Materials, ASTMC-177.


References (continued)

9. Flower, Robert G. "Smarter Windows," June 1987, Practical
Homeowner Magazine, pages 68-69. Additional comments on Aerugel
are presented in the June 1989 issue of Practical Homeowner , page 8.
10. Reflective radiant barrier tests conducted by the Research and
Development Division of the Florida Energy Center at Cape Canaveral.
Data printed in a 4-page brochure from Roy & Sons, Inc. may be
requested from Roy & Sons, Inc., P.O. Box 2223, Irwindale, CA
91706, manufacturers of residential radiant barriers.
11. "R-FAX Insul-Foil, Insulation Applications," information card,
1986. 2 pages. Data may be requested from R-FAX Technology,
Manufacturer of Foil Insulation, 661 East Monterey Avenue, Pomona, CA
91767, (714) 662-0662 or (800) 662-0663.
12. "Radon Detectors," July 1987, Consumer Reports magazine, pages
440 to 446. Consumer Reports, P.O. Box 2480, Boulder, Colo 80322.
13. Heat Recovery Ventilation for Housing: Air-To-Air Heat
Exchangers. 1984. 31 pages. Prepared by the National Center for
Appropriate Technology, P.O. Box 3838, Butte, Montana 59702-3838.
For sale by the Superintendent of Documents, U.S. Government Printing
Office, Washington, D.C. 20402, phone (202) 783-3288. Cost: $2.25
as of August 1987. Ask for report number 061-000-00631-1. This text
thoroughly explains pertinent concepts about air-to-air heat
exchangers.
14. Brochure on Tyvek® Housewrap from Dupont. Similar data was
presented on a single-page form (E-45684-2) from Dupont; it was
distributed as sales information and printed on Tyvek ®.
15. "Energy-Saving Housewraps." September 1987, Practical Homeowner
magazine, page 84.
16. Home Improvements Manual. 1982. 384 pages. Pages 352 to 379
deal with energy saving renovations. Copies can be requested from The
Readers Digest Association, Inc., Pleasantville, New York.
17. Metz, Donald. Superhouse. 1981. 150 pages. Garden Way
Publishing, Pownal, Vermont 05261.
18. Shurcliff, William A. Super Insulated and Double Envelope
Houses. 1981. 182 pages. Brick House Publishing Company, P.O. Box
134, Acton, MA 01720.
19. Marshall, Brian, and Robert Argue. The Super Insulated Retrofit
Book; A Homeowner's Guide to Energy Efficient Renovation. © 1981,
208 pages. Renewable Energy in Canada, 107 Amelia Street, Toronto,
Canada M4X 1E5,
20. Coffee, Frank The Self Sufficient House. 1981. 213 pages.
Holt, Rinehart & Winston, 383 Madison Avenue, New York, NY 10017.
21. "An Energy Miser," from Home Plan Ideas, Spring 1985, Better
Homes and Gardens Building Ideas. Pages 24 to 29. Published by:
Special Interest Publications, Publishing Group of Meredith
Corporation, 1716 Locust Street, Des Moines, Iowa 50336.
22. McGuigan, Dermot, and Amanda McGuigan. Heat Pumps. 1981. 202
pages. Garden Way Publishing, Pownal, Vermont 05261.
23. Eklund, Ken, and David Baylon. Design Tools for Energy Efficient
Homes, 3rd edition. 1984. 126 pages. Ecotope, Inc. 2812 East
Madison, Seattle, WA 98112, (206) 322-3753. Ecotope also provides
advisory services to builders on how to meet current building energy
codes.

References (continued)

24. Energy Efficient Housing: A Prairie Approach. 1980 and 1981. 31
pages. Energy Research Development Group, Department of Mechanical
Engineering, University of Saskatchewan (Canada). Reprinted with
permission in May 1982 by Wisconsin Division of State Energy,
Department of Administration, 101 South Webster Street, P.O. Box 7868,
Madison, Wisconsin 53707.
25. "Heat-Recovery Ventilators," October 1985, Consumer Reports
magazine, pages 596 to 599. Consumer Reports, P.O. Box 2480,
Boulder, Colorado 80322.
26. Besant, R. W., R.W. Dumont, and D. Van Ee. An Air-to-Air Heat
Exchanger for Residences, Department of Mechanical Engineering,
University of Saskatchewan, Saskatoon, Saskatchewan S7N OWO
(Canada). These are the original plans for a homemade air-to-air heat
exchanger core, made from polyethylene vapor barrier, plywood spacer
strips, nails, acoustical sealant, and plywood exterior. (This
publication is no longer in print.)
27. Besant, Robert, Rob Dumont, Tom Hamlin, and Greg Schoenau.
Solplan 6: An Air Exchanger for Energy Efficient Well Sealed Houses.
1985. 25 pages. Published by the Drawing-Room Graphic Services, Ltd,
P.O. Box 86627, North Vancouver, British Columbia V7L 4L2
(Canada). A do-it-yourself manual on making a heat exchanger out of
coroplast (special plastic sheeting material), sealant, plywood, and
other commonly available materials. Copies can be obtained from: U
Learn, 126 Kirk Hall, University of Saskatchewan, Saskatoon,
Saskatchewan S7N OWO (Canada).
28. Watson, Donald. Designing & Building a Solar House. Your Place
in the Sun. 1977. 281 pages. Garden Way Publishing, Pownal,
Vermont 05261. The copyright for this text is held by Donald Watson.
29. Insulation Manual. 1971 and 1979. 149 pages. Published by NAHB
Research Foundation, Inc., 627 Southlawn Lane, P.O. Box 1627,
Rockville, MD 20850.
30. McConnel, Charles. Plumbers and Pipe Fitters Library. Welding-
Heating -Air Conditioning. 1977. 374 pages. Published by Howard W.
Sams & Co., Inc., 4300 West 62nd Street, Indianapolis, IN 46268.
The table listing "Ground Temperatures Below the Frost Line" is on
page 60.
31. Mazria, Edward. The Passive Solar Energy Book. 1979. 435 pages.
Rodale Press, Inc., 33 E. Minor Street, Emmaus, PA 18049.
32. Anderson, Bruce. Solar Energy: Fundamentals in Building Design.
1977. 374 pages. McGraw Hill Book Company, P.O. Box 402, Hightstown
NJ 08520.
33. Kreider, Dr. Jan and Dr. Frank Kreith. Solar Energy Handbook.
1981. 1,000+ pages. McGraw Hill Book Company, P.O. Box 402,
Hightstown NJ 08520. Page 16-8 demonstrates heat loss and gain
through double-glazed windows. This reference book is an excellent
source of detailed information about solar energy.
34. Best, Don. "Home Energy Update," October 1986, Practical Homeowner
magazine. Section on Solar energy, pages 74 and 111.
35. Lowe, Carl. "Water-Saving Toilets," August 1986, New Shelter,
pages 26 to 30. The article describes and tests a number of water-
saving toilets. New Shelter magazine was replaced by Practical
Homeowner magazine, which stopped publication in the early 1990s.

References (continued)

36. Butler, Lee Porter. Ekose'a Homes Natural Energy Conserving
Design, 2d edition. 1978, 1980. 112 pages. Ekose'a Inc., 573
Mission Street, San Francisco, CA 94105. When in business, this firm
marketed plans and consultation for the gravity geo-thermal envelope
home and other energy conserving designs.
37. Fleming, W. S., and Associates, Inc. Manual of Acceptable
Practices for Installation of Residential Earth-Coupled Heat Pump
Systems. 1986. 32 pages. Prepared by W. S. Fleming and Associates,
Inc., 5802 Court Street Road, Syracuse, New York 13206. Copyright by
Niagara Mohawk Power Corporation, 300 Erie Boulevard West, Syracuse,
NY 13202. Text was distributed with other data from ClimateMaster
Geo-thermal pumps, 2007 Beechgrove Place, Utica, NY 13501.
38. Heat Pump Manual. EPRI EM-4110-SR. 1985. Electric Power
Research Institute, 3412 Hillview Avenue, Post Office Box 10412, Palo
Alto, CA 94303.
39. Richter, H. P., and W. C. Schwan. Wiring Simplified, 33rd
edition. 1981. 160 pages. Park Publishing, Inc., 1999 Shepard Road,
St. Paul, Minnesota 55116.
40. Hottel and Howard. New Energy Technology: Some Facts and
Figures. 1971. Massachusetts Institute of Technology Press, 55
Hayward Street, Cambridge, MA 02142. This text was the source of the
table on properties of heat storage materials.
41. Nisson, J. D. N., and Gautam Dutt. The Superinsulated Home Book.
1985. 316 pages. $36. John D. Wiley & Sons, 605 Third Avenue, New
York, NY 10158-0012. This book provides a comprehensive coverage of
theoretical and practical considerations in design and construction of
superinsulated houses. This text should be studied carefully before
starting any major energy renovation or construction project.
42. "Cool tubes cooled off." October 1989, Practical Homeowner
magazine, pages 9-10.
43. “Your Roof’s Insulation may have you seeing red.” By Kent
Langholz. This data found by search of the Internet (Sept 2003), in
reference to Phenolic Foam Boards, absorbing water, resulting in
severe roof corrosion. Also shrinkage of the board size over time,
causes loss of effective insulative performance.

Related References

The below listed references contain useful data on energy efficiency
in housing. Although they are not specifically used for information
in this book, they can provide additional clarification of some
concepts of energy conservation.

1. Shurcliff, William A. Super Insulated Houses and Air-To-Air Heat
Exchangers. 1988, 153 pages, $19.95. Brick House Publishing
Company, P.O. Box 134, Acton, MA 01720. This book explains both the
history of energy-efficient housing development as well as the details
of current designs of energy efficient housing types. The book
analyzes causes of indoor air pollution, presents details on air-to-
air heat exchangers, explains in understandable terms the physics of
airflow technology, and describes commercially available air-to-air
heat exchangers.

2. Watson, Donald, and Kenneth Labs. Climatic Design. 1983. 280
pages. $44. McGraw-Hill Book Company, P.O. Box 402, Hightstown NJ
08520. This text provides considerable theoretical detail on the
principles of heat loss and gain in residential houses. Also included
are methods for designing energy-efficient houses based upon local
climate -- sun, wind, temperature, and humidity -- to maintain
comfortable indoor temperatures year-round. Parts of this book seem
inaccessible, except to engineers.
3. A Homeowner's Guide to Insulation and Energy Savings. 1989.
Owens-Corning Fiberglas Corporation, Fiberglas Tower, Toledo OH
43659. This 32-page booklet published by Owens-Corning provides
useful data on installing fiberglass insulation in new construction
and in retrofitting. It provides practical tips for the amount of
insulation to be used and methods of installing the insulation in
attics, walls, floors, and crawl spaces. As of September 1989, this
booklet was available free of charge. Write Owens-Corning at the
above address or phone 1-800-GET-PINK.
4. Your Guide to Windows & Doors, by the editors of Rodale's
Practical Homeowner Magazine. 1986. 30 pages. Practical Homeowner,
27 Unquowa Road, Fairfield, CT 06430, (203) 259-9877. This
publication provides data on window types, framing, glazings, and
special features. It also lists manufacturers who market these
products. Additional data is provided on interior storm windows,
storm window repair, sun control film, new and replacement doors and
door manufacturers.
5. Air-to-Air Heat Exchangers, (brochure FS-191), October 1985, 4
pages. This information can be requested from the U.S. Department of
Energy, P.O. Box 8900, Silver Spring, MD 20907, (800) 523-2929. The
U.S. Department of Energy has information about a number of topics
available to the public.

House Construction Information

1. Holloway, Dennis, and Maureen McIntyre. The Owner-Builder
Experience, How to Design and Build Your Own Home. 1986. 185 pages.
Rodale Press, Inc., 33 E. Minor Street, Emmaus, PA 18049. This text
presents a wide variety of information on house design, planning, and
construction. Additionally, it explains various concepts in energy-
efficient housing.
2. Jackson, Frank. Practical Housebuilding for practically everyone.
1985. 258 pages. McGraw-Hill Book Company, P.O. Box 402, Hightstown
NJ 08520. This text explains housebuilding from the standpoint of a
person who had rarely used tools previously yet successfully built his
own house. It is a "can-do" approach to building one's own house
although the project may seem insurmountable at times.
3. Durbahn, Walter E., and Elmer W. Sundberg. Fundamentals of
Carpentry. Practical construction, 5th edition. 1982. 519 pages.
Van Nostrand Reinhold Company, Inc., 135 West 50th Street, New York,
NY 10020. This book explains the technical aspects of standard house
construction, providing excellent details about wood frame
construction.


Manufacturers and Product Suppliers
(Most of this data is from 1988 through 1992)
1. Furnace and boiler manufacturers (as of 1992)
Below are listed the BTU/hour output of the smallest size furnaces
available for the high-efficiency models. The rated efficiency from
the company literature is included. If lower output furnaces are also
available, the smallest available output with its efficiency is
listed.

Addison Products Company, 215 North Talbot, Addison, MI 49220
Amana Refrigeration Inc., Amana, Iowa 52204
41,000 BTU/hr (gas) @ 90%; 36,000 BTU/hr @ 82%
Bard Manufacturing Company, 520 Evansport Road, Bryan, OH 43506
48,000 BTU/hr (gas) @ 95.8%; 43,000 BTU/hr @ 65%
Carrier Corporation, P.O. Box 70, Indianapolis, IN 46206
61,000 BTU/hr (gas) @ 92.2%; 20,000 BTU/hr @ 70.5%
Clare Brothers Ltd, 223 King Street, Cambridge, Ontario, N3H-4T5,
Canada
Coleman Company, Inc., P.O. Box 19014, Wichita, KS 67204-9014
41,000 BTU/hr (gas) @ 92.1%; 34,700 BTU/hr @ 72%
GlowCore Corporation, P.O. Box 8971, Cleveland, OH 44136
60,000 BTU/hr @ 89% or 91% (gas)
Heat Controller, Inc., P.O. Box 1089, Jackson, MI 49204
45,000 BTU/hr (gas) @ 93.3%
Heil-Quaker Corporation, P.O. Box 3005, LaVergne, TN 37086-1985
38,000 BTU/hr @ 94.7% (gas); 41,000 BTU/hr @80.5%
Hydrotherm, Rockland Avenue, Northvale, NJ 07647
Lennox Industries, Inc., P.O. Box 80900, Dallas, TX 75380-9000
38,000 BTU/hr (gas) @ 97%; 22,000 BTU/hr (gas) @ 68.1%
Magic Chef Air Conditioning Company, 421 Monroe Street, Belvue, OH
44811
39,000 BTU/hr (gas) @ 97.1%; 32,000 BTU/hr @ 74.6%
Rheem Manufacturing, 5600 Old Greenwood Road, Ft. Smith, AR 72906
45,000 BTU/hr (gas) @ over 90%; 34,000 BTU/hr @ 72.2%
Trane Company, 6200 Troup Highway, Tyler, TX 75711
40,000 BTU/hr (gas) @ 95%
Weil-McLain, Blane Street, Michigan City, IN 46360
45,000 BTU/hr (cast iron boilers) @ 85.3%
Williamson Company, 3500 Madison Road, Cincinnati, OH 45209
48,000 BTU/hr (gas) @ 95%; 84,000 BTU/hr (oil) @ 83%
Yukon Energy Corporation, 378 West County Road D, St. Paul, MN 55112
66,000 BTU/hr (oil) @ 90.8%; 40,000 BTU/hr (gas) @90+%



2. Special vapor barrier material and vapor barrier sealants (as
of 1992)

TenoArm film (8 mil, long lasting vapor barrier 9' x 100')
TenoArm seal (to seal the vapor barrier joints)
Resource Conservation Technology, Inc., 2633 North Calvert Street,
Baltimore, MD
21218, (301) 366-1146
Acoustical Sealant (for polyethylene). Tremco, 10701 Shaker Blvd.,
Cleveland, OH 44104
Contractor Sheathing Tape, # 8086 (also suitable for polyethylene and
Tyvek® Housewrap).
3M Contractor Products, 3M Center, St. Paul, MN 55144-1000

3. Housewraps (vapor permeable) (as of 1992)

1) Tyvek ® Housewrap. Dupont, Fibers Marketing Center, Center Road,
Wilmington, DE 19898
2) Barricade Building Wrap. Simplex Products Division, P.O. Box10,
Adrian MI 49221.
3) Airtight-Wrap. Parsec, P.O. Box 38527, Dallas, TX 75238.
4) Rufco-Wrap. Raven Industries, P.O. Box 1007, Sioux Falls, SD
57117.
5) Tu Tuf Air Seal. Sto-Cote Products, Drawer 310, Richmond, IL
60071.
6) Versa-Wrap. DiversiFoam Products, 1901-13th Street N.E., New
Brighton, MN 55112.

4. Blow-in / Foam-in insulations (as of 1992)

1) Air Krete, Inc. (“Air Krete” insulation); E. Brutus Street, P.O.
Box 380, Weedsport, NY 13166, (315) 834-6609.
2) Ark-Seal International Corporation; (“Blow-in Blanket,”
insulation), 2185 S. Jason Street, Denver, CO 80223, (800)
525-8992.
3) CP Chemical Company; (Tripolymer ® phenolic foam), 39
Westmoreland Avenue, White Plains, NY 10606, (914) 428-2517.

5. Reflective insulations (as of 1992)

For a listing of the manufacturers of reflective insulation, write:
Reflective Insulation Manufacturers Association, P.O. Box 2454,
Irwindale, CA 91706 (or search on the internet)

6. Geo-thermal heat pumps (Manufacturers of geo-thermal heat
pumps, as of 1992)

Addison Products, 7050 Overland Rd., Orlando, FL 32810
Bard Manufacturing Co., P.O. Box 607, Bryan, OH 43506
Climate Control Inc., 881 Marcon Blvd., Allentown, PA 18103
ClimateMaster ®, P.O. Box 25788, Oklahoma City, OK 73179
Command-Aire Corp., P.O. Box 7916, Waco, TX 76714
Florida Heat Pump Corp., 601 N.W. 65th Ct., Ft. Lauderdale, FL
33309
Heat Controller, P.O. Box 1089, Jackson, MI 49204
Mammoth Refrigeration, 13120-B County Rd. 6, Minneapolis, MN 55441
Marvair, 3570 American Dr., Atlanta, GA 30341
Thermal Energy Transfer Corp., 1290 US 42 N., Delaware, OH 43015
Water Furnace Int'l., 9000 Conservation Way, Ft. Wayne, IN 46809

7. Foam board covering and adhesives (as of 1992)

1) Styrofoam brand Foundation Coating is designed to cover foam
insulation boards to give it a finish similar to stucco. Styrofoam
brand Construction Adhesive was developed for use with Styrofoam
insulation boards (Dow Chemical Company, Styrofoam brand Products
Dept. P.O. Box 1206, Midland, MI 48674).
2) PL 200 Panel and Foam Adhesive and PL 300 Foam Board Adhesive
(Contech, 7711 Computer Avenue, Minneapolis, MN 55435) is designed
for use with foam insulation boards and will not degrade or "eat" the
foam as some other construction adhesives do.

8. Phenolic foam insulation boards (as of 1992)

1) Koppers Company, Inc., 1901 Koppers Building, Pittsburgh, PA
15219, (412) 227-2000. (They made this product from 1981-1989)
2) Genstar Roofing Products Company, Inc., 5525 MacArthur Boulevard,
Suite 900, Irving, TX 75038, (214)580-5600.
3) U.S. Insulfoam Co. (PhenoliCore brand), P.O. Box 710, 1993 Belford
North Drive, Belvidere, IL 61008, (815) 547-7722.

9. Solar water heaters (as of 1992)

1) Sunflare 2000: Write: U.S. Solar Corporation, P.O. Drawer K,
Hampton, FL 32044.
2) Heat Pipe passive solar water heater: Energy Engineering,
Albuquerque, New Mexico.
3) Solartechnics, 360 Center City, Bangor, Maine 04401

10. Ventilation system accessories (as of 1992)

Filters and wall caps. For wall caps with dampers, it will be
necessary to remove the backdraft damper on the intake cap. X-Change
Air Corporation recommends the wall caps be mounted at least six feet
apart to prevent cross-contamination of airflows.

Broan Mfg. Company, P.O. Box 140, Hartford, WI 53027. This company
also makes Heat Recovery Ventilators.
Model # Description
641 6" duct, Aluminum wall cap with backdraft damper and birdscreen,
$33.95
643 8" duct, Aluminum wall cap with backdraft damper, $45.95

Air Changer (see address under "Heat exchange companies")
Catalog No. Description
OVH6 Two 6" outside vent hoods for intake and exhaust,
includes washable intake filter, $53.00


American Aldes (see address under "Heat exchange companies")
Part No. Description
23014 6" intake or exhaust grille with bird guard, $16.70
22042 6" roof cowl, brown, low profile, $49.40
22036 6" roof cowl, gray, low profile, $49.40
23956 Filter housing for 6" diameter duct, $34.60
23804 Replacement filter for part #23956, $6.80

Star Heat Exchangers (see address under "Heat exchange companies")
7" and 8" duct, Ejection exhaust nozzle. Allows side by side
installation of exhaust and intake without danger of cross-leakage
$25.00
7" and 8" duct, Intake nozzle with bird screen $20.00

Xetex (see address under "Heat exchange companies")
Model # Intake and exhaust hood Model # Intake Filter Housing
HD-4 4" duct size $14 IF-4 4" duct size $15
HD-5 5" duct size $15 IF-5 5" duct size $16
HD-6 6" duct size $16 IF-6 6" duct size $17

11. Blowers and fans that one could use in a homemade air-to-air
heat exchanger. Such items can be purchased from a hardware store, or
from local heating, ventilation, or "electric motor" suppliers. It
may be possible to locate motors of some wholesale fan/blower
manufacturing companies through their distributors or repair people.
Local distributors might be found in the Yellow Pages under "Electric
Motors," "Heating," or "Ventilation." Below are some manufactures of
blowers and fans.

1) Tjernlund Products, 1601 Ninth Street, White Bear Lake, MN
55110-6794; (615)426-2993; 800-255-4208
This company markets duct pipe fans typically available in hardware
stores (as of September 2003). See comments on page 153 about fan
blade shape and airflow problems (and how to resolve them). They are
easily adapted for use in the homemade air-to-air heat exchanger,
described on pages 97-109.

2) Some other sources for duct booster fans, found by search of the
Internet, as of September 2003.
A. Smarthome.com has duct boosters for 4” to 12” diameter ducts.
B. ESP ENERGY; 1615 Newberry; Racine, WI 53402; (262) 681-9288;
1-888-551-9288. Has in-line duct fans for 4” to 12” ducts, plus
several other similar fan versions.
C. Empire Ventilation Equipment Co. 35-39 Vernon Blvd; Long Island
City; NY 11106 (718)728-2143. Has in-line duct fans for 6” to 12”
ducts.
D. Aero-Flo Industries; P.O. Box 358; Kingsbury, IN 45645-0358; (219)
393-3555. Has 6” in-line duct fans.

3) Ancor Industries, 1220 Rock Street, Rockford, IL 61101, (815)
963-7100. (This company apparently out of business, as of 1994.)
This company sold fans easily installed in duct pipes. Their
Superbooster duct boosters were intended for use in heating and
cooling duct pipes to improve airflow to selected rooms. Motors were
low-wattage and were made in 120 Volts (AC), 24 Volts (AC), and 240
volts (AC); sound insulated with foam rubber. I found the 6-inch size
fans very well suited for the homemade heat exchanger (using 14-inch
wide aluminum plates) that I describe on pages 97-109. Below were the
sizes and specifications during the time they were made.

Duct size Model Volts Amps Watts total CFM Price Shipping
5 inch 15-0070 115 V 0.37 15 80 $39.95 $3.00
6 inch 15-0071 115 V 0.40 20 110 $39.95 $3.00
7 inch 15-0072 115 V 0.44 23 150 $39.95 $3.00
8 inch 15-0073 115 V 0.46 25 200 $39.95 $3.00

4) Broan Manufacturing Company, P.O. Box 140, Hartford, WI 53027.
This company makes various ventilation products. (As of September
2003) Broan makes Heat Recovery Ventilators, and has fans and blowers
available as replacement parts for a large variety of ventilation
units they market. Below are listed a few of these fan and blowers
with some related statistical data (from 1990). To vary motor speeds
for these models, model no. 57 solid state infinite speed control, 3
amp capacity ($22.95) is suitable.

Broan Centrifugal blowers
Part # total CFM Used For Model # Price Amps
97006021 100 ventilator 360 $58.60 0.7
97006022 160 ventilator 361 $61.30 1.0

Broan Axial room-to-room fans: Units complete with housing
Part # total CFM Used For Model # Price Amps
6 inch fan 90 Ventilating 512 $33.95 1.0
8 inch fan 180 Ventilating 511 $78.95 1.5

Broan Axial range fans: Fan and bracket only
Part # total CFM Used For Model # Price Amps
97005163 190 range hood 42000 $21.90 0.8 (two speeds)
97005161 160 range hood 40000 $21.20

Broan Twin centrifugal blowers ("dual blowers")
Part # total CFM CFM/stream Used For Model # Price Watts
97006152 200 100 range hood 76000 $46.40 225
97005985 360 180 range hood 88000 $66.80 155
97007542 440 220 range hood 89000 $87.40 270
97006023 200 100 Ventilator 362 $75.70 115
97006024 300/310 150 Ventilator 363, 383 $81.60 165
97007074 960 480 Ventilator 366 $167.90 390

5) Northern Tool & Equipment Co., P.O. Box 1499, Burnsville,
Minnesota 55337-0499. 1-800-533-5545. This mail-order company
occasionally has surplus fans and blowers at a low cost that could
potentially be used in a heat exchanger.

Below are listed other types of fans and blowers made by wholesale
manufacturers. (as of 1992)

1. Howard Industries, P.O. Box 287, Milford, IL 60953. This
manufacturer makes a number of sizes of low-wattage axial fans. The
manufacturer sells only to distributors. Write to the manufacturer
for a listing of distributors. Below are listed a few of the 115 volt
models.

Model # CFM Diameter Watts Price (plus power cord)
2672 70 cfm 4.7" 17 W. $25.74 $1.11
4315 100 cfm 4.7" 19 W. $25.74 $1.11
6052 120 cfm 6.72" 10 W. $52.76 $1.11
5812 180 cfm 6.72" 18 W. $55.54 $1.11
5804 240 cfm 6.72" 30 W. $42.85 $1.11
0101 560 cfm 10.0" 37 W. $55.46 $1.11
Power cord, 24" long, Model No. 6-170-672, $1.11 each

2) Fasco Industries, Inc., Motor Division Headquarters, 500
Chesterfield Center, Suite 200, St. Louis, MO 63017. The
manufacturer sells only to wholesale distributors. It may be
possible to locate some of their distributors or repair people through
the yellow pages. The manufacturer makes a number of different types
of blowers and fans for specific commercial applications. Below are
specifications of a few of the many blowers made by Fasco.

75 cfm, Model B75, 115 V, 0.59 amps.
105 cfm, Model 50757-D500, 115 V, 0.55 amps.
120 cfm, Model 50746-D500, 115 V, 0.72 amps.
160 cfm, Model 50755-D500, 115 V, 1.0 amp.
180 cfm, Model B47120, 115 V, 1.95 amp.
212 cfm, Model A212, 115 V, 1.25 amps.
320 cfm, Model 50756-D500, 115 V, 1.3 amps.



Index


Air exchange rates, 19-21, 86, 87, 104-108
Air-Krete®, 3, 5, 113, 141
Air-to-air heat exchanger, 20, 82-110
schematic diagrams, 21, 82-85
see also : Heat exchangers
Attic access ladder, 131
Attic ventilation, 17, 28, 60, 117

Backward double wall, 32-34, 62, 68-73
condensation, 34, 116
retrofitting, 76-81
schematic, 32, 33
Beadboard, 2, 5
Blowers, 104-109, 142-44
Blow-in Blanket®, 4, 5, 75, 113, 141
British thermal unit (BTU), 1, 35-41, 43-47, 49-50
Building shape
in heat loss/gain, 42, 43

Cellulose insulation, 2, 5
Clerestory windows, 12
Condensation
walls, 6-8, 116-18
windows, 14, 15, 129, 130
Cooling demands, summer, 40-42
Cooling hours, summer, 122, 123
Cooling tube, 27, 48-50, 64
Crosshatch wall, 30, 31, 34, 75
Curtain wall, 33, 68-70, 74-77

Degree-days, 51-57, 122, 123
Design temperatures, 122, 123
Double walls, 30-34

Earth homes, 22-24
Earth tubes, 27, 48-50, 64
Envelope homes, 22, 23, 25-27, 48

Fans, 103-109, 142-44
Fiberglass, 2, 5, 34, 111-14
French seam, 8, 76


Geo-thermal heat pump, 45-47, 142
Ground temperatures, 125
Groundwater temperatures, 125

Heat exchangers, 20, 82-110
company listings, 88-95
coroplast, 96, 97
counterflow, 82-84, 96, 97
crossflow, 82-84, 96, 97
duct system, 65, 108
heat pipe, 85
homemade models, 96-110
rotary, 85, 86
vent plan, 65, 108
Heat loss, sources of, 38
Heat recovery ventilators,
see : Heat exchangers
Heating costs, 54-58
Heating degree-days, 51-57, 122, 123
Heating system, 140-42
sizing the system, 44-47
Heat pump, geo-thermal, 45-47, 140
Humidity, relative, 14, 15, 34, 116-18

Infiltration, 19-21
barriers, 21, 22
Insulation, 2-7, 34, 111-13, 141, 142
cutting batts and rolls, 4
installing layers of, 62
suggested levels, 51-53
types, forms, 2-6
ventilation, 17, 28, 60, 116
Insulative sheathing, 9, 30, 58, 113
Internal gains, 35-40
Isocyanurate foam, 2, 3, 5, 111-13

North, true, 126

Overhang designs, 118-20
proper dimensions, 119-21

Party wall, 30, 31
Perlite, 2, 5
Permeability, vapor, 116, 118
Polyethylene, 8, 9, 67-73, 77-80
Polyurethane (urethane), 2, 3, 5
Pull-down ladders (insulation), 131

Radiant barriers, 3, 5, 16-18, 42, 111-14
in superinsulation, 65-67
installation, 17, 18, 60, 66
Radon, 19, 65
Reflective foil, 3, 5, 16-18, 42, 111-14
Relative humidity, 14, 15, 34, 116-18
Retrofitting, defined, 74
Retrofitting insulation, 74-81, 113, 114
superinsulation, 75-81, 113, 114
Rock wool, 2, 5, 111-13
Roof
framing, 60, 120
windows, 11, 12
R-values, 2-5, 34-40, 111-14

Shower heads, water-saving, 132
Solar gain
examples, 37, 40, 124
gain and loss through windows, 11
tables, 11, 128, 129
Solar home, 22, 24, 25
Solar position, 127
South
deviation from, 126
window gain, 11, 37, 40, 124, 126, 128, 129
Space heating requirements, 39
Styrofoam, 2, 5, 142
Summer heat gain, 39-42
Sun's path in summer in winter, 10
Sun, also see : Solar
Superinsulated house, 23, 27, 28
basement, 70
single-story, 36-42, 68, 69
two-story, 71-73
Superinsulated wall, 62-81, 115
curtain wall assembly, 77, 78
framing, 78
plywood gussets, 77, 80, 81
retrofitting data, 74-81


Temperature gradients of walls, 34
TenoArm film (vapor barrier), 9, 76, 141
Thermal mass, 43, 44
Thermal storage, 47
Thermax foam, 2, 3, 5, 111-13
Toilets, water-saving, 133, 134
Tripolymer ® foam insulation, 3, 5, 141

Urethane foam, 2, 3, 5

Water heating, 132, 133
Windows
clerestory windows, 12
condensation, 14, 15, 129, 130
framing, 14, 63, 64
heat gain chart, 11, 37, 40, 124, 126, 128, 129
insulation, 13, 14
low "E" windows, 15, 16
multiple-pane, 14, 15
orientation, 9-12, 41, 126
shading, 119-21
Winter heat loss, 36-39

Vapor barriers, 6-9, 27-32, 59, 68-73, 77-80
French seam, 8, 76
installation, 59
TenoArm film, 9, 76, 141
Vapor permeability, 116-18
Ventilation, 20, 21, 61, 64, 65, 87, 106-10
insulation, 17, 28, 60, 117
Ventilation system dampers, 108
see also : Heat exchangers, vent plan
Vermiculite, 2, 5







Retrofitting Basement Insulation

Basement walls are subject to excessive winter heat loss when not
insulated. It is possible to reduce basement heat loss significantly
by retrofitting insulation on basement walls and floors.
The technique described here provides a "superinsulated" basement
wall arrangement (about R-27) with basement floor insulation (about
R-6). The basement floor insulation will reduce the final ceiling
height by about 2.5". Before proceeding with basement renovations,
check with your local building inspectors to find out the code
requirements.
1. To serve as the top plate of the basement wall, attach a 2x4 to
the bottom of the first floor joists, so that the inside wall position
will be about 8" from the existing concrete wall. This will provide a
3.5" space between the wall studs and an additional 4.5" space from
the concrete wall to the beginning of the wall studs. The top plate
of the future basement wall should have a piece of polyethylene vapor
barrier (about 16" wide) placed between the bottom of the first floor
joists and the top plate. The top plate can be attached by nailing,
or by pre-drilling holes and holding the top plate in place with 3"
wallboard screws, installed by a 3/8" variable speed reversible drill.
2. It is necessary to seal the space between the floor joists, the
top plate of the (future) basement wall, and the bottom of the first
floor subfloor. This space can be bridged by use of a foam board.
Two-inch-thick beadboard is sufficient for the job. If this is not
available, one can get the necessary thickness of foam board by
obtaining ¾" beadboard and bonding three boards together (a single
thickness of ¾" beadboard is not sufficiently strong). Beadboard
sheets can be obtained in sections ¾" thick by 13 5/8" by 48".
Stagger the ends of the beadboard by ½" when gluing together, as shown
in the diagram on the next page (page 148). This will approximately
match the angle that the beadboard must have when angling upward to
meet the first floor beneath the exterior wall position. The boards
can be glued together using Liquid Nails ® (latex) panel and
construction adhesive. Apply the glue over the surface of one foam
board. Place the second board on top of it in the proper position.
Apply the glue to this surface and place the third board on top of
this. You can prepare a number of these three-section foam boards at
one time. Once all the glue has been applied, place weight evenly on
top of the boards while the glue is drying. (For example, I assembled
about ten of these three-section foam boards at one time; I stacked
them on top of each other and placed some boxes of books and magazines
on top of the stack and allowed a couple of weeks for the glue to set
before removing the boxes.)
3. Once the foam is set, cut it to widths to fit the space between
the floor joists. Wedge the foam board in the space between the floor
joists. Glue it in place around the four sides with Liquid Nails.®
Cover the board with a vapor barrier, ensuring that the vapor barrier
in this space is sealed to the sides of the floor joist, to the bottom
of the first floor subfloor, and to the vapor barrier section on top
of the top plate of the (future) basement wall. I elected to use a
section of radiant barrier* as a vapor barrier, since it has a perm of
about 0.5 and it readily holds in place with caulk and glue; it has
some rigidity and has useful insulation value.
4. The space behind the foam board should be filled with fiberglass
or rock wool insulation. However, allow a day or two for the glue to
set so that you do not force the foam board out of position while
stuffing in the fiberglass. Sealing the space between the floor
joists is a very meticulous and time-consuming project.



*One type of radiant barrier is made as double-sided foil mounted on
building paper -- available from radiant barrier manufacturers such as
R-Fax, 661 East Monterey Ave., Pomona, CA 91767.




See page 151 for further details on retrofitting basement floor
insulation.


5. Sealing around ducts and pipes can be problematic. When
insulating near pipes, make sure you put as much insulation as you can
between the pipe and the exterior wall. If most of the insulation is
not between the pipe and the exterior wall, there is increased risk of
freezing of pipes and drains. It is unsafe to "bury" a pipe within
wall insulation when that pipe is closer to the outside wall--freezing
and rupture could result. Frame around basement windows and add an
additional inside window (sealed to the vapor barrier) when
retrofitting interiorly.
6. Decide whether you intend to install floor insulation. All wood
that directly contacts the basement floor must be pressure-treated; in
the event that moisture seeps through the basement floor, it will not
rot pressure-treated wood. If floor insulation is planned, one
approach is to attach pressure-treated 2x4s (lying flat) around the
perimeter of the basement, with pressure-treated 2x2s spaced every
16”, with two thicknesses of ¾” beadboard (as the floor insulation)
between the wood framing members. (I used masonry nails to attach the
pressure-treated 2x4s and 2x2s – see details on page 151.) Cover the
wood and insulation with a vapor barrier (and a radiant barrier, if
desired) before attaching the ¾” plywood subfloor. The 2x4 wall rests
on the ¾" plywood subfloor. For details on basement floor insulation,
see my narrative on page 151.
7. The concrete basement wall should be covered with a "moisture
barrier" until above grade; this will ensure that water seepage
through the concrete wall will not soak into the fiberglass
insulation. This moisture barrier can be 6 mil or 4 mil polyethylene;
however, the moisture barrier must stop above grade to allow venting
space for any water that gets into the insulation (as by vapor getting
through the vapor barrier) -- such "trapped" water must be allowed to
escape as a vapor. I first nailed ½” thick pressure-treated boards
near the top of the basement wall (above grade) and stapled the
moisture barrier to these boards to hold it in place. The moisture
barrier should eventually be joined to the floor and wall vapor
barrier sections. (Leave enough spare polyethylene to later make that
attachment.)
8. Using a plumb bob for alignment, position the 2x4 bottom plates
(for the stud wall) beneath the previously attached top plate. Then
cut the wall studs to the proper height. Toenail the studs in
position or use metal brackets to secure in place.
9. Fit the 6" batts in the 4.5" space between the moisture barrier
and the row of wall studs. It is best to install the 6" batts at
right angles to the wall studs, starting from the bottom upwards until
the 4.5" cavity is filled. Fit the 3.5" fiberglass batts between the
wall studs.
10. I did a very labor-intensive arrangement on the wall, to place
the wiring and electrical boxes interior to the vapor barrier. On the
2x4 studs I attached the vapor barrier, and sealed it to the moisture
barrier at the floor. Then I attached 2x2s directly to the studs, on
top of the vapor barrier. I found a slightly shallow version of
electrical boxes, which I attached to the sides of the 2x2s. I put
wiring through the 2x2 spaces. Then I attached a radiant barrier to
the 2x2s and put 1x2 furring strips on top of the radiant barrier. (I
pre-drilled holes, and screwed in long screws that went through the
1x2s, the 2x2s, and then into the 2x4 studs.) I spaced the electrical
box position to allow for the additional 1x2 furring strip thickness.
Then I covered the wall with gypsum wallboard.
11. You can then cover the subfloor with tile or carpeting, as
desired. With the basement floor and walls carefully sealed by a
vapor barrier, the final result is nearly an airtight seal, which also
blocks all openings for radon infiltration into the basement.


Getting Started on Retrofitting an Existing Home

Now that you have read all the data in this book, where do you
start?
The first step is to determine the nature and severity of the heat
loss from the house. It is possible to have a professional analysis
of the locations of heat loss, or one can determine the problems by
observation and inspection.
If the house seems drafty, the first step might be to caulk and
weather-strip around doors and windows. If the house is already
fairly well sealed, the first step might be to enhance fresh air
supply prior to "tightening up" the house further.
I moved into a new home, which met the regional energy requirements
for insulation standards. The air quality already seemed poor when
the house was closed up. Since I had earlier completed my homemade
air-to-air heat exchanger, I began to determine the best location to
install this. I was able to route the second floor bathroom exhaust
vents to the basement by converting our "clothes chute" to an exhaust
air plenum. Without such a pre-installed "air plenum," one can route
a 6-inch exhaust pipe (or a rectangular exhaust plenum) to the
basement through a closet space or in the corner of a room and then
cover the duct with wallboard to conceal it. The exhaust air from the
bathrooms is routed to the basement, through a filter, through the
exchanger exhaust fan, through the exchanger, and then through exhaust
pipes to the outdoors. The fresh air is then brought from outside,
routed through a filter; it enters the exchanger and goes through the
fresh-air supply fan and into the basement. At this point it is
possible to provide fresh air supply via ducts to individual rooms.
(This is a very difficult enterprise in a completed home.) I elected
to provide vents between the basement and the first floor rooms. With
an open stairs to the second floor, the fresh air reaches the
bathrooms and hallway exhaust vent for return to the exchanger.
Individual rooms get fresh air when the room doors are open to the
hallway.
While in the attic, I found gaping holes in the attic insulation that
the builders had not covered. My next step was to tighten up the
attic insulation by the following methods. I retrofit a continuous
vapor barrier (see details on page 78). I attached a radiant barrier
to the underside of the roof rafters, from the eaves to the ridge
vent, while allowing venting space above the radiant barrier. I
installed a final insulation thickness of three R-19 batts (R-57
total), except near the eaves where sufficient space was not
available. I did all the attic work in winter to avoid otherwise
unbearable summer attic temperatures. In spring I added continuous
soffit vents and then added ridge vents.
The combination of continuous soffit vents and the ridge vent results
in excellent removal of attic heat in summer. Additionally, the vent
plan reduces the chance of "ice dam" formation in winter. An ice dam
results when the heat of the house warms the roof and melts the snow.
The water from the snow runs down the roof until reaching the
overhang, which is at colder outdoor temperatures. The water is
stopped at the overhang and freezes in an "ice dam." Further melting
of snow causes trapped water at the edge of the roof, which can back
up under the shingles and leak into the attic and house -- causing
significant water damage. Proper attic venting and insulation
prevents this problem.
After the attic insulation/venting project, the next step was
retrofitting basement insulation, as described in these appendix
pages. The basement work is also very time-consuming, yet less
unpleasant than working in the tight spaces of the attic.
If you have an attached garage, sealing and insulating these walls
more effectively can reduce the heat loss between the house and the
garage. The final step in insulation retrofitting may be the exterior
walls. Retrofitting exterior walls will require re-siding the home
once completed. Exterior wall retrofitting can be fairly uncomplicated
for one-story homes with sufficiently wide roof overhangs already
present. With two-story homes or those without sufficiently wide
overhangs, exterior wall retrofitting can be a major undertaking. If
you already have standard wall insulation, exterior retrofitting may
not be economical except in very cold climates or if you have very
expensive fuel costs.


Practical data on retrofitting basement floor insulation

Retrofitting basement floor insulation requires attachment of
pressure-treated framing members to the concrete basement slab. I
used pressure-treated 2x4s around the basement perimeter with pressure-
treated 2x2s spaced every 16" on center as the primary support boards
for the basement floor. I was able to special order beadboard in a
14.5" width to fit between the 2x2s. Alternatively, one could use the
more commonly available 13.5" width of beadboard, and alternate
between 2x2s and 2x4s, on center. I used two thicknesses of ¾"
beadboard between the floor framing, resulting in about an R-6
insulative value. I then installed 4-mil polyethylene on top of the
framing and insulation. I then covered the polyethylene with double-
sided foil radiant barrier. (I used a radiant barrier even though a
reflective air space was not available.) On top of the foil I
attached 4' x 8' sheets of ¾" tongue and groove plywood subfloor. I
then built the walls on top of the plywood, and insulated the
perimeter walls to an 8" thickness, as shown on page 148.
Attachment of the wood framing to the concrete slab can be a lot of
work. The options are (1) using powder-activated nails, (2) masonry
nails, (3) pre-drill the concrete and install plastic anchors,
attaching the wood framing with screws, (4) use a different form of
pre-drilled attachment anchor. The powder-activated nails are quick
and effective; I decided against using them since the device is too
much like a weapon, and occasionally serious injuries have occurred
with use of such "stud guns." I initially tried masonry nails, but
found they would not penetrate our 6-year old concrete without
chipping holes in the concrete and bending the nails. I found plastic
anchors and screws to be fairly effective. However, it is typically
necessary to remove the board to add any additional anchors if the
attachment is not secure enough.
After using some plastic anchors and investigating other anchor
types, I figured that masonry nails might work if pre-drilled in
advance with a masonry bit smaller than the nail thickness. I found
after pre-drilling with a good quality 1/8" carbide-tipped percussion
bit (such as the DeWalt® brand), that the 2.5" Georgia Pacific®
"fluted masonry nails" (which I used for the job) resulted in a strong
attachment to the concrete slab. Typically it took masonry nails
spaced every 16" to firmly attach the 2x2 and 2x4 boards to the slab.
I used a ½" Black and Decker® drill which was equipped with hammer/
drill settings. The "hammer" setting helped the drilling process into
the concrete. After drilling through the wood and concrete for the
full depth of the nail, one should thoroughly suction out the drilling
debris with a "shop vac." It can then take a dozen or more firm blows
with a 4 lb. hammer to drive the nail into the concrete. (The nail
goes through 1.5" of wood and 1" of concrete.) A significant expense
with any pre-drilled method is the cost of the carbide-tipped bits
(about $3 each) which can dull significantly after 10 to 40 holes are
drilled into the concrete. Drilling and hammering into concrete can
be a physically exhausting process, not to mention a very noisy
activity. Both hearing and eye protection are necessary for this job;
knee pads are also advisable. Using Liquid Nails® latex caulk (or
equivalent) under the 2x2 and 2x4 pressure-treated boards enhances the
attachment strength.
To attach the moisture barrier to the inside (concrete) basement
wall, I found it useful to first attach ½" pressure-treated boards to
the basement wall at grade. Use 4 or 6 mil polyethylene sheeting as a
moisture barrier and staple it to the ½" boards to secure it in place,
prior to sealing the moisture barrier to the floor and wall vapor
barriers. (See page 148 for details.) You can attach the pressure-
treated boards to the basement wall by pre-drilling with a masonry
bit, then pounding in 1" masonry nails, spaced every 2 to 3 feet.


Observations on vapor barrier effectiveness

In the winter of 1988 I began retrofitting a vapor barrier in the
unfinished attic of our recently constructed home. I had already
installed the air-to-air heat exchanger in the house a couple of
months earlier, and we had been enjoying the plentiful fresh air it
supplied. As winter arrived, we noticed a dramatic increase in static
electricity in the home; with everything we touched, we tended to get
a shock. It reminded me of my former homes in northern Illinois and
southern Wisconsin, where static electricity was ever-present in
winter -- those homes had little insulation and no vapor barrier. In
our new home, I was installing an attic vapor barrier in the manner I
describe on page 78. I took 3-foot-wide pieces of 4 mil polyethylene
and fit it into the space between the ceiling joists of the upper
floor of the house. I was sealing each 2-foot-wide space between the
joists to the adjacent vapor barrier sections, to retrofit essentially
a continuous air/vapor barrier in the attic. I was closing off
successive sections of vapor barrier, and then moving to the next
section of vapor barrier. On some of the sections, as I closed off
the final seal of the vapor barrier, the vapor barrier began to
inflate with air. I realized I had just closed off a large passageway
for heated house air that typically leaked out of the house. It
seemed to happen most obviously when there were a lot of openings for
electrical wires entering the attic space. Through all of these
drilled holes, large amounts of house air were continuously escaping.
By the time I had gotten half of the attic vapor barrier retrofit, the
static electricity problem in the house was significantly diminished,
and as I continued the project, all static electricity problems ended,
even though the low outdoor humidity of winter remained. All
successive winters have shown no return of static electricity
problems.
The house construction was probably tight enough that we might have
had only mild static electricity problems. With the addition of the
air-to-air heat exchanger, we exhausted a higher proportion of the
stale, moist house air through the exchanger and replaced it with
fresh air (dry, outdoor winter air), which was pre-heated by the air-
to-air heat exchanger. Even with newer, tightly-constructed homes,
much of the house air is lost continuously through unintentional
openings into the attic. Along with this air loss is moisture loss,
making the indoor air uncomfortably dry (resulting in static). By
retrofitting a continuous attic air/vapor barrier, the movement into
the attic of heated house air (and the moisture it contains) is
blocked.

Attic radiant barrier

When I retrofit the attic with a vapor barrier, I also increased the
attic insulation level to 18" (three thicknesses of 6" batts). While
installing the vapor barrier and additional insulation, I also
installed a (double-sided) foil radiant barrier against the roof
rafters in the attic. As I proceeded with the attic project, one
morning I noted an unusual frost pattern on the external roof
shingles. The cold night air left frost on half of the roof -- the
area that I had already insulated; no frost was visible on the roof
over the attic that I had not yet retrofit. Yet the pattern of the
frost ended abruptly -- not explainable by the attic floor insulation
that was several feel below the roof. I then realized that the frost
pattern exactly matched the last section of radiant barrier I had
installed. The radiant barrier was therefore reflecting radiant heat
from the house, back into the house. The areas that lacked a radiant
barrier allowed the radiant heat to escape from the house, to warm the
roof surface and to keep the frost from forming on the roof in that
area. I was able to track the progress of my insulation job from the
outside of the house, as I saw more and more morning frost visible
further along the roof, as more of it had reflective insulation.
Similarly, when the roof gets covered with snow, our roof is about the
last in the neighborhood to melt the snow; this occurs because little
of the house heat escapes to warm the roof. The attic eave vents and
roof ridge vents are also an important part of an effective radiant
barrier. I installed the eave and ridge vents months later, in
spring, after completing the internal insulation work of the attic.
Radiant barriers are known to block the entrance of summer heat into
the attic and house. My observations show there is value in a radiant
barrier, also in cold weather, to reflect escaping radiant heat back
into the house.

Air-to-Air Heat Exchanger -- Update information (as of 1995)

In 1988 I designed and constructed a homemade air-to-air heat
exchanger. (This is described on pages 96 to 109). I installed the
heat exchanger that same year in our new home, using the Superbooster
duct fans as described on pages 109 and 143. After more than 6 years
of faithful service, the intake fan motor wore out. Being unable to
obtain a replacement Superbooster (the company apparently went out of
business), I then replaced the fan with a Tjernlund* fan designed for
6" ducts. I soon found the new fan had a difficult time maintaining
adequate airflow. The motor often labored and ran down to very low
RPMs. This was particularly the case if the inlet airflow was even
slightly restricted. By comparing the Superbooster to the Tjernlund
fan, the main apparent difference was with the fan wheel itself. The
Superbooster fan wheel was made from a circular aluminum disc, cut and
shaped to have 10 pie-shaped blades to move the air. The Tjernlund
fan wheel was a plastic disc, molded to have 4 fan blades. The
Tjernlund fan wheel caused a larger volume of air to move since the
blades struck a much larger area of air per revolution. If the inlet
air was restricted (by filters and bends in the ventilation system),
the Tjernlund fan ran down. Yet under restricted airflow the
Superbooster fan seemed to actually speed up. I found that by
reducing the size of the Tjernlund fan blades, I could prevent the
motor from being overloaded by reducing its airflow capacity to be
better suited for the 6" ducts and filters of the heat exchanger. The
below diagram shows how to trim the fan blades. It is necessary to
make exact measurements and careful cuts (such as by using a coping
saw, and then filing the edges smooth) to keep the fan wheel in
balance for when it is reinstalled on the motor.



When I first installed the heat exchanger, I used a screened inlet to
keep insects out, and then I used an in-line dust filter. Over time,
I found conventional ("furnace") filters are NOT effective in keeping
dust out of the heat exchanger; dust also eventually clogs the fan
blades and motor. I found that ½" thick foam rubber (such as used for
carpet padding or for thin cushioning) makes a very effective filter
for dust. I covered the outside air inlet with ½" foam rubber and
made an additional 10" x 10" in-line filter (using foam rubber) to
keep dust out of the exchanger. I also used the same filtering system
on the exhaust side, prior to air reaching the exchanger. It is
typically necessary to remove the intake filters and clean them (using
soap and water) usually every few months since they get progressively
clogged with dust over time.
I later obtained “filter foam” from a store specializing in foam (and
foam mattresses). The filter foam I obtained in 1-inch thickness. I
now use the filter foam as the in-line air filter. I also use the new
filter foam to replace the previous ½” foam rubber, to cover the
outside air inlet for the air-to-air heat exchanger duct. I use the
filter foam to replace the ½” foam rubber for the inside of the
exhaust air plenum, to block dust from ever reaching the heat
exchanger on the exhaust side.
I also used this type of filter foam to cover the two intake vents
for our whole house ventilation ducts, for the forced air heat
system. (Actually I removed the intake grills, and found I could fit
filter foam inside that location.) I first covered the internal duct
with “hardware cloth” (which is a wire mesh). I put the filter foam
against that wire mesh. The intake air must then flow through the
filter foam, before it enters the ductwork. Now when I clean the
“furnace filter” I clean 3 filters: both of the intake filters AND the
regular filter inside the air handling unit of the forced air heater /
air conditioner. The extra intake filters block additional dust from
entering the forced air ductwork of the house.

* Tjernlund Products, 1601 Ninth St., White Bear Lake, MN 55110-6794