As I recall, warming gas is pretty linear, so I think the difference between ambient and internal is going to be more important than whether the temp is steady or fluctuating.

Houses aren't adiabatic so you're going to loose temp through radiative heating as well as convection. Therefore, ambient temp diff is going to be of greater importance.

I'm trying to imagine a house perfectly insulated. Why would it make a diff whether the temp were steady or fluctuating? Is this one of those PV=nRT thingies?

B