[pjerem]

That's what norms are for.

If minimal thermal requirements are written in the law, even the cheapest builder must build a highly insulated home. In my country, it's mandatory to have well insulated home, to prove (with tests) that you respect the norms, and it's also mandatory to have renewable heat source (mainly heat pumps). Sure, it costs a little more, but with the rise of real estate prices, it's still way cheaper to build well insulated houses.

The building cost since those new norms increased about maybe dozens of thousands euros. It's not even a lot given the exceptional thermal comfort you get from your money.