"The heat that goes up the chimney of 99% of all homes is enough to heat another house."

Multilevel houses.

I am reminded of the satirical cartoon that explained how business worked, A 2 level toilet - bosses on top, workers below....

Wait on, if the heat that goes up the chimney of 99% of all homes is enough to heat another house, then what do we do with all the other houses except that one?