Quote:
Originally Posted by Daox
I think we could use it to compare houses.
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That's exactly what I was thinking.
I first thought about hooking up a Kill-a-watt to the furnace. That would tell me how much ON time it has per day, week, etc., but this (and recording my gas meter every morning) would more likely help with finding the efficiency of the furnace and/or heating system as a whole.
The analogy with coastdown testing keeps floating around in the pool of scum that I call my head. What would be frontal area on a car is the total surface area of the house, through which heat can escape. This means walls, roof and floor. The best weather conditions would be thick clouds (minimal solar gain), no wind, almost constant temperature for as long as possible. Also, not being in the house for as long as possible helps (I've noticed that watching the 170 watt LCD for 30 minutes can raise the temperature in the room by 0.25*C). And, of course, the more cooldown tests go into an average, the better.
Among the differences are that aero drag depends on the square of speed (or, more generally, the dependance is polynomial), while the relation between heat loss and temperature difference is (inverse) exponential. Also, the heat loss through the floor will be different than through the walls and roof, since the ground's temperature doesn't change much. Could this be analogous to the rolling resistance component of drag? And how do cooldown tests with different outdoor temperatures compare?
Anyway, I think that there may be a way to compare the thermal efficiency of houses with two numbers, surface area and a number (thermal coefficient). More thinking, more thinking, more thinking... Darn, that hurts!!