Typically with passive houses/"pretty good" houses that have low inherent ACH they then have HRV/ERVs installed for mechanical ventilation, to provide good air

Typically with passive houses/"pretty good" houses that have low inherent ACH they then have HRV/ERVs installed for mechanical ventilation, to provide good air quality. It's possible for such a building to have better air quality than normal construction. At the same time, the theory isn't always embodied correctly. The ventilation design may be poor or make wrong assumptions (like requiring bedroom doors to be open) or the homeowner may unwittingly turn it off or not change the filter periodically. I have a ~40 year old house that has some energy-efficient features, but ultimately isn't very tight and doesn't need ventilation. I still hope to install an ERV in the next few years, though, just because I think the benefits of good ventilation will be so strong.