Originally Posted By: tanstaafl.
The only reason you put heat in a house at all is to replace the heat that has been lost through radiation, either into the ground or into the air surrounding the house.

The amount of heat lost through radiation is proportional to the fourth power of the difference in temperature (in degrees Kelvin) between the radiating body and the outside source that is absorbing the heat. Lessening this difference greatly reduces the amount of heat loss.

Most heat loss into the air, and all heat loss into the ground (unless the ground near you is transparent to far IR, which it isn't) is through convection or conduction respectively -- not radiation. Energy flow through both convection and conduction goes linearly with the temperature difference, not to the fourth power. But even so, I think your actual point still stands...

Peter