Energy efficiency is very much a priority here, like there are rules about insulation, government support to insulate older houses and upgrade heating systems and so on, and of course fossil fuels are taxed increasingly to comply with the climate goals and such. They teach you in school how to air out your place efficiently, like don't leave the window open a little for a long time but open wide briefly etc. I honestly don't know anyone who doesn't let air in in winter. Not doing that is thought to be very unhealthy for the indoor climate and air quality. Like you are basically told that you'd get sick without enough fresh air indoors. I'm still kind of astonished that Americans might keep their windows closed for months. I never imagined that.