> I wonder how expensive it would be to get widespread usage of better stoves, heat pumps or co-generation + district heating with centralized gasified burning. Everything could be locally built.

Do you want cheap and efficient, or do you want locally built?

Very expensive. If you want to invest, first step would be making inefficient houses efficient, aka insulation. Problem is that, a lot of older housing ventilation is built on it being leaky...

The city of Szeged in Hungary did this recently. You can find some numbers from there.