Troy NY Passive Solar Renewable Energy Home- 2nd Edition
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nick pine
May 21, 2011, 7:35:08 AM5/21/11
to sunspace, mbi...@nesea.org, kham...@soudertonsd.org
http://video.google.com/videoplay?docid=-5312373664958749521&ei=MN5WSbiUNKO6qAOS\p6GgCw&q=passive+houses#
We've seen this before. A direct gain house with windows that lose
lots of heat at night and on cloudy days with low-temp mass in the
living space and a low solar heating fraction and 4 kW of PVs is
heated with wood and
natural gas and electricity to the tune of some 500 gallons of oil per
year.
Where are the inexpensive passive solar air heaters that lose no heat
on cloudy days and the higher temp water tank or ceiling mass that
stores more heat than room temp mass?
>... passive solar homes use a fraction of the energy their normal counterparts use
Mr. Barton says this one is 2/3 solar-heated and the windows provide
500 gallons of oil per year. So without the sun, it would need 1500
gallons of oil per year, about 150 million Btu per winter in a 6894 F
DD heating climate, which makes its thermal conductance 150million/
6894/24h = 907 Btu/h-F.
That is surprisingly high, for a house that looks like it's about
24'x32'x16'-tall with an R25 south wall and R45 other walls and an R52
roof. Perhaps it has major air leaks, or too much thermal bridging, or
too many south windows.
> The Borton's charming Troy, New York... 250 square feet of windows on the south side of his house generate approximately 60 million btus of heat, which is the equivalent of 500 gallons of heating oil.
NREL says 700 Btu/ft^2 of sun falls on a south wall on an average 26.5
F December day with a 34.9 F high in Albany, so 250 ft^2 of R4 south
windows with 50% solar transmission would collect 0.5x250x700 = 87.5K
Btu/day and lose about 24h(65-26.5)250/4 = 57.8K Btu, for a net gain
of 29.8K Btu. If the house needs 24h(65-26.5)907 = 838.1K Btu, it is
100x29.8K/838.1K = 3.5% solar heated on an average day in December,
and less on cloudy days, with its room-temp mass.
A 24'x32'x16'-tall house next door with 8" R32 SIP walls and an R40
attic floor and 128 ft^2 of R4 windows and 30 cfm of air leakage would
have a 128/4 = 32 Btu/h-F window conductance + 1664/32 = 52 for the
walls + 768/40 = 19 for the attic + 30 for air leaks, totaling 133 Btu/
h-F. It would need about 24h(65-26.5)133 = 122.9K Btu/day of heat, or
122.9K-68.2K = 54.7K Btu, with 300 kWh/mo of indoor electrical use.
If 1 ft^2 of R2 twinwall polycarbonate passive air heater glazing with
80% solar transmission gains 0.8x700-6h(80-30)1ft^2/R2 = 410 Btu/day,
it needs 54.7K/410 = 133 ft^2 of air heater glazing. With more, we
could make hot water for showers and store 5x54.7K = 274K Btu of heat
for 5 cloudy days with a solar heating fraction close to 100% in 274K/
(140-80)/62.33 = 73 ft^3 of 140 F water that cools to 80 F over 5
days, in a 4'x6'x3'-tall plywood box with a 10'x12' folded EPDM rubber
liner.
> The Borton house is so efficient that the morning sunlight that comes through a window turns dishes on a rack into a radiator for the kitchen.
Is this more efficient than morning sunlight that falls on the
floor? :-)
Nick
We've seen this before. A direct gain house with windows that lose
lots of heat at night and on cloudy days with low-temp mass in the
living space and a low solar heating fraction and 4 kW of PVs is
heated with wood and
natural gas and electricity to the tune of some 500 gallons of oil per
year.
Where are the inexpensive passive solar air heaters that lose no heat
on cloudy days and the higher temp water tank or ceiling mass that
stores more heat than room temp mass?
>... passive solar homes use a fraction of the energy their normal counterparts use
Mr. Barton says this one is 2/3 solar-heated and the windows provide
500 gallons of oil per year. So without the sun, it would need 1500
gallons of oil per year, about 150 million Btu per winter in a 6894 F
DD heating climate, which makes its thermal conductance 150million/
6894/24h = 907 Btu/h-F.
That is surprisingly high, for a house that looks like it's about
24'x32'x16'-tall with an R25 south wall and R45 other walls and an R52
roof. Perhaps it has major air leaks, or too much thermal bridging, or
too many south windows.
> The Borton's charming Troy, New York... 250 square feet of windows on the south side of his house generate approximately 60 million btus of heat, which is the equivalent of 500 gallons of heating oil.
NREL says 700 Btu/ft^2 of sun falls on a south wall on an average 26.5
F December day with a 34.9 F high in Albany, so 250 ft^2 of R4 south
windows with 50% solar transmission would collect 0.5x250x700 = 87.5K
Btu/day and lose about 24h(65-26.5)250/4 = 57.8K Btu, for a net gain
of 29.8K Btu. If the house needs 24h(65-26.5)907 = 838.1K Btu, it is
100x29.8K/838.1K = 3.5% solar heated on an average day in December,
and less on cloudy days, with its room-temp mass.
A 24'x32'x16'-tall house next door with 8" R32 SIP walls and an R40
attic floor and 128 ft^2 of R4 windows and 30 cfm of air leakage would
have a 128/4 = 32 Btu/h-F window conductance + 1664/32 = 52 for the
walls + 768/40 = 19 for the attic + 30 for air leaks, totaling 133 Btu/
h-F. It would need about 24h(65-26.5)133 = 122.9K Btu/day of heat, or
122.9K-68.2K = 54.7K Btu, with 300 kWh/mo of indoor electrical use.
If 1 ft^2 of R2 twinwall polycarbonate passive air heater glazing with
80% solar transmission gains 0.8x700-6h(80-30)1ft^2/R2 = 410 Btu/day,
it needs 54.7K/410 = 133 ft^2 of air heater glazing. With more, we
could make hot water for showers and store 5x54.7K = 274K Btu of heat
for 5 cloudy days with a solar heating fraction close to 100% in 274K/
(140-80)/62.33 = 73 ft^3 of 140 F water that cools to 80 F over 5
days, in a 4'x6'x3'-tall plywood box with a 10'x12' folded EPDM rubber
liner.
> The Borton house is so efficient that the morning sunlight that comes through a window turns dishes on a rack into a radiator for the kitchen.
Is this more efficient than morning sunlight that falls on the
floor? :-)
Nick
Don Hull
May 21, 2011, 7:54:39 AM5/21/11
to suns...@googlegroups.com
I just saw a demonstration of Thermacoat paint. Sprayed on the inside attic roof. It keeps the attic from going more than 15 degrees above ambient. They intended to do the vinyl siding the next day. Can also be put on inside walls, like primer to insulate.
Don Hull
Donald Hull
Geothermal Specialist
Ground Source HVAC
610-306-6245
groundso...@gmail.com
www.groundsourcehvac.com
Call When You're Serious About Saving Energy
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