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Lacustral wrote:

Does painting the outside walls of a house white help much to keep it cool?


On a 90 F day, 1 ft^2 of R20 light-colored wall outside 80 F air would gain
(90-80)1ft^2/R20 = 0.5 Btu/h. A dark wall in full sun might have 250 Btu/h
= 0.1741x10^-8((T+460)^4-(90+460)^4), so T = 236 F, and (236-80)/1ft^2/R20
= 7.8 Btu/h, eg (7.8-0.5)8x40 = 2340 Btu/h more for an 8'x40' wall.

Do people living in the desert tend to have light houses?


They should, but some "planned communities" in Arizona specify _maximum_
reflectivities for walls and roofs, based on aesthetics... :-)

Nick