• posted on September 20, 2004, 9:23 pm
A 10x10 room in a moderate winter zone needs 22btu/sqft or 2200btu which is about 650w. With a 900w heater, what is the maximum temp I could maintain with an outside temp of -5C/23F? Moderate winter zone is defined as a minimum 0C/32F.
Here are the room's construction details:
There is a 5' vinyl double glazed patio door (unknown R value). The room is facing west with another exposed wall facing south above an enclosed garage (not sure if the garage ceiling is insulated). 8' ceiling with R20 insulation under a pitched roof. Wind is not an issue here, about 150kms north of Seattle. Exterior walls are 2x4 so probably R12 insulation.
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• posted on September 21, 2004, 12:44 pm

If it needs 2200 Btu PER HOUR at 70 F inside and 0 F outside, its thermal conductance is 2200Btu/h/(70F-0F) = 31.4 Btu/h-F. A 900 W (3071 Btu/h) heater would make 3071 = (T-23)31.4, so T = 23+97.8 = 120.8 F :-)

You might enjoy painting the south wall dark and covering it with a single layer of polycarbonate glazing with an air space to make a thermosyphoning air heater.
Nick
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• posted on September 21, 2004, 1:30 pm
Sam wrote:

Run a detailed heat loss calculation, then figure out how many BTUs a 900W heater produces.