mog said:
I'm sure there must be a formula somewhere to figure that out... x(BTUs) = temp drop x area x time or such?
I bielieve the formula to calculate btus required to offset heat loss in winter or heat gain in summer is:
BTU = ( Temperature difference * area in sq ft ) / R value of insulation
if the R value is different for ceiling, walls, floor calculate a btu figure for each surface and add together.
I suppose you could use different temperature differences for each surface if you thought there was a big enough temperature difference from outside the roof as opposed to outside the floor.
I guess that's why roofs and floors of houses have more insulation than walls.
This gives the BTUs to maintain the heat loss or offset the heat gain, You would need more BTUs to raise or lower the starting room temperature. The source for the formula suggested doubling the number of BTUs but I don't know the basis for that.
Too many BTUs and the AC / Heater will short cycle and use to much energy or produce big room temperature swings. The hvac experts seem to say a longer run time is more efficient and more comfortable.