So it seems in practice the main way you achieve this certification is to dramatically cut heating losses by using a lot of insulation and make the house essent

So it seems in practice the main way you achieve this certification is to dramatically cut heating losses by using a lot of insulation and make the house essentially air-tight. Obviously you can’t have an air-tight house for very long, you need fresh air. So you have explicit vents for incoming and outgoing air, and you run the incoming air (which is fresh, but not the temperature you want) through a heat exchanger with the outgoing air (which is stale, but is at the temperature you want). This recovers most of the heat you put into your inside air, so you need very little heating to maintain the desired temperature. This is actually a really good thing, I think. The minimum airflow rating these houses have to meet is of course going to be suboptimal, but the hard part of airproofing is already done and it’s easy for the homeowner to simply beef up the heat exchanger and air pump to get ideal airflow. The homeowner can also install an air quality filter on the airpump and now their entire house has filtered air. Great way to get that PM2.5 level down to where it should be!