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Re: How to provide heat to a small extension

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Posted by N. Thornton on October 17, 2004, 7:27 pm
johnty1@hotmail.com (johnty) wrote in message

Electric costs around 3x gas to run.
Flat plate solar space heating is far cheaper than costly water
heating systems. This is the one form of solar that has very
reasonable install cost and pays back well. See alt.solar.thermal.


Posted by Gary on October 18, 2004, 2:42 am
N. Thornton wrote:

I am working on replacing my forced air heating with floor radiant
with solar assist -- I've found these sites to be helpful for
understanding whats involved in all the various radiant heating options:

These sites offer a lot of installation and design
documentation (you may have to dig around through the architect,
designer, professional pages to find the good stuff):

These guys do both electric and hydronic:

Some interesting products:


Posted by nicksanspam on October 18, 2004, 12:25 pm
 johnty1@hotmail.com (johnty) considered:

About 23'x8'.

You might check out unglazed solar roof panels from Energie Solaire, or
replace the roof with a layer of polycarbonate glazing over two layers
of polyethylene film over a polycarbonate ceiling. The space between the
film layers could be filled with air during the day and soap bubble foam
at night from a shop vac blowing air through a pipe full of holes in a
10% detergent solution. The vac might turn off when foam begins to push on
a screen over an air return near the top and the screen pushes the arm of
a microswitch.

In Phila, 620 Btu/ft^2 falls on the ground on an average 30 F January day,
so a square foot of room with an R2 cover and 80% solar transmission might
collect 0.8x620 = 496 Btu and lose 6h(70-30)1ft^2/R2 = 120, for a net gain
of 376 Btu, or 8x23x376 = 69.2K Btu/day, under an 8'x23' roof. You might
get some sun in south windows as well.

You might keep the room an average 65 F on a 30 F day if 24h(65-30)G < 69.2K,
ie G = 680/R < 82.4, which makes R = 8.26, ie US R-value 8.26 (metric U0.69)
walls and ceiling, like 2" of white foamboard. You might store 69.2K Btu in
69.2K/(70-60) = 6920 Btu/F of thermal mass cooling from 70 to 60 F, eg an
8'x23'x1.5' thick concrete slab, or a thinner layer of overhead warmer water.


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