`  ::I agree that the idea is somewhat premature and not suitable for inclusion in a Wikipedia article. But it occurred to me that we might encounter some absurd expression like W/W while discussing the rate of heat flow at a given power expenditure needed to maintain an equilibrium in temperatures where ``Fo/W`` would be clearer. With respect to global warming passive systems may be preferrable and active systems counter-productive. High R-value is definitely low carbon but a building needs to allow for an exchange of gases too.   `