Comment Re: Indoor air (Score 4, Informative) 117
No they're not, otherwise people would be dying from lack of oxygen.
Virtually yes. That's why they have a ventilation system that takes air from the outside, runs it through a heat exchanger with the expelled inside air.
The houses are air-pressure-tested according to DS/EN 13829 and DS/EN ISO 9972:2015
The air/pressure loss must not exceed 1,5 l/s pr. m heated area at 50 Pa.