Attic insulation and an Attic Catwalk

[Energy Conservation in Housing]

The Attic “Catwalk”

After working in a few attics, in houses where I have lived over the
years, I began to dread going back into the attic space, mainly due to
how difficult it can be to move around in the attic. One slip of the
foot off the joists in the attic, and you can put your foot through
the ceiling of the room below.

As I was thinking about my upcoming attic project (and dreading the
whole experience), the idea hit me one night . . . MAKE A CATWALK.
It won’t be tough or expensive, but it would make moving around in the
attic a lot easier and safer.
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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.
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The attic I was to work in, had trusses made from 2x4s. The bottom
chord of the truss was 3.5” off the floor of the attic (which is the
ceiling of the top floor). My plan was to make a catwalk about 7”
above the floor of the attic, and I figured that a 2 foot width was
sufficient, to run the length of the attic. I had initially planned to
start with 2x2s attached to the bottom chord of the truss. Finding
only pressure-treated 2x2s, I decided to use 2x3s, flat against the
bottom chord of the truss, and then to use 2x3s at right angles to
the lower 2x3s, with 3/8” plywood on top of the upper 2x3s.

I cut the first layer of 2x3s at 2 foot lengths each, one for each of
the trusses. I pre-drilled 4 holes in the 2x3s, so that I could
attached them flat, to the bottom chord of each truss, using 2.5” long
drywall screws.



The 2.5” width of the lower 2x3s actually gave a larger surface to
attach the 2x3s running at right angles to the trusses. (It was much
easier to attach, compared to the 1.5” width of the truss bottom
chord.) The lower 2x3 boards not only raised the catwalk by 1.5” –
but it also allowed me to notch around any wires or wood pieces I
encountered when making the catwalk.

The upper 2x3 boards were typically 8 feet long. I pre-drilled the
top 2x3s at the ends and at 2 foot intervals, for attachment to the
lower 2x3s; I attached them using 2.5” drywall screws. I used 3 rows
of the upper 2x3s, to support the 2 foot wide plywood ––– at the ends
and in the middle. That way the thin plywood never had to span much
more than 8 inches between each supporting 2x3.



I obtained pre-cut pieces of 2’ x 4’ x 3/8” plywood. Typically I pre-
drilled holes in the plywood, between 6 and 9 holes, positioned to
attach to the underlying 2x3 boards. I used 1¼” or 1 5/8” screws to
attach the plywood. All the catwalk pieces went together really fast
using an electric drill, with a #2 Phillips tip.

As I attached the boards, I didn’t keep the catwalk perfectly straight
(like one would a finished floor), since I was aiming around some of
the supporting wood structures in the attic.

Before I installed the plywood pieces of the catwalk, I put a 6”
insulation batt under the location of the catwalk, with the vapor
barrier facing down against the attic floor. Right before I attached
the plywood, I used some loose fill insulation from the attic to fill
in the spaces between the final set of 2x3s.



The final catwalk ran the length of the attic (which was 30 feet); it
was 2 feet wide, and about 7” above the floor of the attic. That left
about 4 feet to the peak of the attic. Certainly that was not enough
space to “walk” in. Yet it was easy to move around in the attic by
doing a low walk. More often, I got around by doing a “crab walk” –
sort of lifting with my hands and feet and sliding a bit on my
bottom. With knee pads, it is similarly easy to walk on hands and
knees on the catwalk.

My eventual plan was to increase the insulation depth from the
original 6” to around 15” –– as well as to add a radiant barrier to
the inside of the roof. You might ask, “What good is a 7” catwalk if
you want 15” of final insulation?” Simple . . . The last step was
cutting (unfaced) 8” thick insulation, the width of the catwalk, to
cover the catwalk once the attic project was completed. With 23” wide
insulation blankets, that was about 32 pieces (23” x 26”) to cover the
catwalk. If later entering the attic space, it is an easy matter to
move the 2-foot sections of insulation aside, do your work, then
replace the insulation.

In my previous house (17 years earlier), I retrofit a continuous attic
vapor barrier, using 4 mil polyethylene sealed to the bottom chord of
the trusses and to the top of the exterior wall near the eaves (as I
describe on page 78 of Energy Conservation in Housing). I found the
process painfully slow. Not having vast amounts of time to do the
project, I decided to do a less exact vapor barrier installation. To
get a vapor barrier, I used 3.5” (R-13) insulation blankets, with the
vapor barrier facing down against the attic floor. I then covered the
top of that insulation, with more insulation to get the final depth I
wanted.

Whenever I moved off the catwalk, I placed boards against the bottom
chord of the truss. Typically they were 4’ long “shelf boards” which
were usually about 10” to 12” wide. I could then move to the eaves,
using around 5 to 7 of these boards to support my body weight. To
reach the eaves, I was lying on my stomach across the boards, and I
was barely able to reach the top of the exterior wall. (I used a
“bicycle helmet” to protect my head from the nails which went through
the roofing material.) In retrospect, having the boards a few inches
longer would have been helpful, since the 4-foot boards could barely
span 3 trusses. One side or the other kept slipping off the edge of
the ceiling joists / roof truss bottom chord.

The first step was “moving” the original insulation. I was once a
“fan” of loose fill insulation. After my last insulation experience,
I really dislike loose fill. One can pick up an insulation blanket, 2
feet wide by 8 feet long with little effort. Just try moving that
much loose fill. You have to move it by the handfuls. And the
dust ! ! ! Loose fill dust is much worse than dust from insulation
blankets. For the first couple of sections, I stuffed the loose fill
into large plastic (“lawn / leaf”) bags. On the adjacent sections, I
“threw” handfuls of the loose fill to the sections I had finished.
Despite a dust mask, the rest of me was soon covered with loose fill
insulation dust. I found I could use goggles for only short periods
of time, since they tended to fog up. Without goggles, it was easy to
get insulation dust in my eyes.

Back to the steps:
1. Move the existing insulation. I found a broom and a “leaf rake”
were helpful in scooping the insulation closer to me so I could either
bag it or move it to adjacent sections.
2. Next attach double-sided reflective foil to the top chord of the
truss (or to the attic rafters, as described in the Radiant Barrier /
reflective foil sections of Part One of Energy Conservation in
Housing, pages 17 and 18). I actually used the radiant barrier ALSO
as an insulation stop. It is probably best to use “perforated” double-
sided radiant barrier for the first 6 feet or so, from the eaves,
since it will be in contact with some of the insulation. Typically
for the first 3 to 4 feet from the eaves, I stapled the radiant
barrier to the inside of the top chord of the truss (see the middle
diagram, on page 18). Once away from the eaves, I stapled the radiant
barrier to the bottom of the top chord of the truss (see the right
diagram on page 18 of Energy Conservation in Housing). The ridge vent
space at the top of the attic needs to stay “open” to allow proper
attic ventilation, so don’t seal that off with radiant barrier.
3. Put the insulation batt / blanket, with the vapor barrier down
against the attic floor.
4. Put another blanket of 6” to 8” insulation at right angles to the
layer between the ceiling joists / truss chords, at the eaves, to
start the second layer of insulation. The second layer of insulation
needs to be “unfaced” –– that is, it should have NO vapor barrier on
the additional layers. (For my “loose fill” insulation, the 6” batt
served additionally as an insulation stop to retain the loose fill
AWAY from the eaves.
5. Move to the next section of attic, and repeat the process. (I
typically did a 4-foot section of attic at a time, on one side of the
attic. Once I got to the end of the attic, I then did the other side
of the attic.)

I decided to retain the original loose fill insulation away from the
eaves AND away from the catwalk, and away from the area near the attic
access panel. By lining the sides of the catwalk with insulation
blankets (about 15” total depth), the loose fill did not spill onto
the catwalk.



To insulate the attic access panel, I stapled a vapor barrier to the
attic side of the access panel board. Then I stapled a frame of
cardboard to the panel, which I made to hold 7 or more inches of
insulation. (The insulation fits on top of the attic access panel,
and the cardboard box “frame” holds the insulation in place.) I then
used weather-stripping around the trim of the access panel opening, so
that it makes a fairly airtight seal when the attic access panel is
put back in place.

Radiant Barriers and Attic Insulation

For nearly 2 decades, I have been a big “fan” of using reflective foil
(“radiant barriers”) in attics and walls. I could tell the
substantial difference that radiant barriers made in reducing attic
heat gain in summer. So I make it an important point to include
reflective foil when doing attic insulation projects. I always plan
on using double-sided reflective foil, with a ventilating air space on
both sides of the foil, whenever possible. (What does a radiant
barrier look like? Imagine a thin layer of aluminum foil bonded to
both sides of a thick paper, to give it more strength.)

Recently I ran across a web-site (of a reflective foil company), that
demonstrated clearly the advantages of reflective foil in blocking
summer heat gain in attics. At the time of this writing, the image
can be found on this web-site:

http://www.afs-foil.com/pages/hotbox.htm

Their above “hot box” experiment shows the temperature difference
between an attic with and without a radiant barrier, by simulating the
difference, using infra-red heat lamps.

On one section, they have a radiant barrier covering unfaced R-19
fiberglass insulation. At the bottom of the insulation is a
thermometer which reads 93.2 degrees F.

On the other section, they have the same amount of conventional
insulation (unfaced R-19 fiberglass insulation) with NO radiant
barrier. At the bottom of the insulation is a thermometer which reads
152.5 degrees F.

There is a difference of 59 degrees F between the two sections. This
difference is due to the radiant barrier’s ability to reflect radiant
heat away from the insulation.

Their experimental numbers were arrived at after a six hour period,
with a surrounding (“ambient”) air temperature average of 84 degrees.
However, it took only a half hour for both simulations to reach these
temperatures.

It would be very difficult to block the same amount of radiant heat
with conventional insulation. Conventional insulation does not
effectively block radiant heat.

Heat loss and gain happens in 3 ways: convection, conduction, and
radiation.

• Convective heat can be slowed by windows, walls, ceilings, vapor
barriers, and infiltration barriers.
• Conductive heat is slowed by conventional insulation.
• Radiant heat is blocked by radiant barriers.

Eighty percent (80%) of radiant heat passes through most building
materials and ordinary insulation. The function of radiant barriers
is clearly demonstrated by the above “hotbox” experiment.

To see the dramatic difference between convection and radiation heat
transfer inside the house, look no further than your kitchen. Compare
the conventional oven to the microwave oven. Pre-heat the oven to 400
degrees, put a mug of water inside, and take it out 2 minutes later.
Then compare a same size amount of water in a mug, and put it 2
minutes in the microwave oven (on high setting). The difference is
dramatic; the microwave oven can raise the water temperature quickly.
That shows the difference between radiant heat transfer and convective
heat transfer.

And that’s what happens in the typical attic; the radiant heat from
the sun heats the attic, and passes right through the insulation. A
radiant barrier effectively reflects the radiant heat away, so there
is less heat to pass into the living spaces of the house.

In winter, the process is reversed: the major source of heat is inside
the house itself. Reflective foil (in the roof and walls, for
example) bounces the radiant heat back into the house, instead of
losing it to the cold outside. (Just don’t expect a winter heat
benefit as dramatic as the summer heat blocking effect of the radiant
barrier.)

[Energy Conservation in Housing]

 I attached this "Hot Box flyer" (PDF image) because the link 

(http://www.afs-foil.com/pages/hotbox.htm), in the above narrative, 

no longer takes you to this hot box flyer image.

The link will probably re-direct you to a business that sells hardware supplies.

That business could eventually help you order reflective foil.