> Add insulation. If your house was built in 1960, was it retrofitted with wall insulation? Put more into the ceiling.

Walls were stripped to the studs approx. 8-10 years ago and new fiberglass insulation installed at that point. Attic has (rough) batt insulation, but I suspect it could be better there. Air handler for the air conditioning system is also in the attic due to, I suspect, no other viable option for the design. Probably some loss there.

> Investigate heat pumps (ground loop for up there) for both hot air and hot water. Solar hot water might be viable. In the US, the tax breaks make solar power a gimme if you have the money.

I'll take a look, thanks. I'll note that I have ductwork for the air conditioning system but the (separate) heating system uses baseboard. Unfortunately, the finished basement doesn't have ductwork installed.