Moderately well sealed houses still exchange quite a lot of air, but if it wouldn't be satisfactory, they often have a fresh air vent usually with a heat exchan

Moderately well sealed houses still exchange quite a lot of air, but if it wouldn't be satisfactory, they often have a fresh air vent usually with a heat exchanger to maintain heating and cooling efficiency. The HRVs and ERVs mentioned in the article are these kinds of devices.