To people who says “they aren’t airtight” are not correct. Living in a country where building houses like this is the norm I can say that they are build to be as airtight as possible to keep in humidity and thereby heat inside. What makes them livable and not a humid moldy plastic bag is a well tuned mechanical ventilation system with a heat regeneration system (air cross flow system, really simple actually) that recovers most of the heat. The ventilation system runs 24/7 and keep the air fresh, more fresh than most conventional houses in fact if it’s tuned correctly that is. But yes the house is as airtight as posible and they pressure test them to ensure they meet the standards. The biggest issue with it is actually cooling them. We have issues here in summer because no method of removing heat is properly implemented yet. But in winter it’s awesome. My heating bill is practically 0.

They aren’t “airtight”, that would awful. They are well-insulated and designed to take advantage of passive solar heating and air exchange cooling. The way roofs and windows and orientation on the land is usually done for western homes is just terribly inefficient for capturing and releasing heat in the right ways. Just some thick walls, a bank of windows facing the sunrise ,and some proper roof vents that can be opened when it’s hot is all most passive houses really are.