re: best heat for my shop ? help
4 may 2004
>i live in south central iowa... i just put up a 40x56x12 ft sidewall shop.
>now it is time for the heat...
piece of cake... see
nrel says 930 btu/ft^2 of solar heat falls on a square foot of south wall
on an average 24.4 f december day in des moines. rotate the shop so one
56'x12' = 672 ft^2 side faces south, if needed, then apply a single layer
of dynaglas corrugated polycarbonate "solar siding" (which comes in 4'x12'
sheets) over a 6" air gap with vent holes through the south wall to collect
0.9x672x930 = 562k btu of sun on an average day.
with r20 wall and ceiling insulation and a 2240 ft^2 ceiling and 1632 ft^2
of non-south walls and heat storage under the ceiling, the air coming out
of the upper vents on an average december day might have temp t (f), where
562k = 8h(70-24.4)672/r1+8h(70-24.4)1632/r20+24h(t-24.4)2240/r20, so t=131 f.
if the ceiling store has an average (130+80)/2 = 105 f temp over 5 cloudy
days, the shop needs 5(8h(70-24.4)2304/20+24h(105-24.4)2240/20)) = 571k btu
for 5 cloudy days in a row. this might come from 571k/(130-80) = 11,424
pounds or 178 ft^3 or a 1120ft^2x2" or 2240ft^2x1" of water in overhead
flat plastic film ducts cooling from 130 to 80 f, with a slow ceiling fan
and a thermostat to bring down warm air as required.