Yes you need active ventilation systems, because the thermal efficiency is highly dependant on the house being airtight - to the point where efficiency scores a

Yes you need active ventilation systems, because the thermal efficiency is highly dependant on the house being airtight - to the point where efficiency scores are calculated by overpressuring the house (basically taping a huge fan into the front door with all other doors and windows shut) and measuring the pressure loss. When applying insulation, contractors have to meticulously use foam to seal everything up. It's a major part of the work when building a new house and just a few mistakes can seriously affect thermal performance.