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Posted by nicksanspam on August 24, 2007, 11:17 am

Like the Brittons? :-)

   Every day is sunny for George and Charlotte Britton of Lafayette Hill...
   The Britton's 2,900-square-foot house is blessed with energy bills
   20 percent lower than one of comparable size... The design of the house
   incorporates "passive" solar principles. There are large double pane
   windows and sliding glass doors on the south side. Inside, tile floors
   and a Trombe wall absorb the sun's heat during the day and radiate it
   at night... A stone fireplace on the south wall of the living area
   provides additional heat during colder months... Britton said...
   "We have a fire every day of the winter."


Posted by Sundug on August 23, 2007, 10:21 pm
On Aug 22, 12:10 pm, nicksans...@ece.villanova.edu wrote:

My large amount of thermal mass with exterior insulation will hold
heat for several sunless winter days. Doug

Posted by nicksanspam on August 24, 2007, 10:29 am

Sounds unbelievable. Got numbers?


Posted by nicksanspam on August 24, 2007, 11:41 am

Where I live near Phila, this could be done, but it wouldn't be easy...

If we keep a 48'x48'x8' house with US R30 walls and an R40 ceiling and
30 cfm of air leaks and A ft^2 of R2 south windows with 80% solar
transmission 75 F on a 30 F average January day and the windows collect
800 Btu/ft^2 of sun for 6 hours per day and they become R15 for 18 hours,
with a thermal conductance G = 6A/(24x2) + 18A/(24x15) + (1536-A)/30 +
48^2/40 + 30 = 138.8-0.097A Btu/h-F and 800A = (75-30)G, A = 132 ft^2
and G = 151.6 Btu/h-F.

If it cools from 75 to 65 over 5 days and 65 = 30+(75-30)e^-(5x24h/RC),
RC = -120/ln((65-30)/(75-30)) = 477 h, so thermal mass C = RCxG = 72,368
Btu/F (a lot.) If we start with a 48'x48'x6" slab with 28,800 Btu/F and
add 4 solid concrete block walls with 23,400 Btu/F, we still need another
20,168 Btu/F, eg 20168/450 = 45 55 gallon water drums? :-)


Posted by Solar Flare on August 24, 2007, 1:17 pm
 WTF is "h-F"?

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