live in a small space heated with a heat pump

Their thin walls cause this to only be a tiny improvement I'd wager (still the best option though). They can even punch holes in their walls, if I tried this with a german drywall I'd break all the bones in my hand.

but I suspect your nation is simply too wealthy to hit the target

This implies environmental protection contradicts wealth (as in "lots of money in one n̶a̶t̶i̶o̶n̶ regional administrative zone"), a common conservative lie. It doesn't, unfettered capitalism does. E.g. the solar business makes fucking bank but is a net positive on the environment. So are lots of other businesses. The definition of wealth is fucked anyway.