https://en.m.wikipedia.org/wiki/Heat_recovery_ventilation https://en.m.wikipedia.org/wiki/Heat_recovery_ventilation This already exists and is starting to gain

https://en.m.wikipedia.org/wiki/Heat_recovery_ventilation https://en.m.wikipedia.org/wiki/Heat_recovery_ventilation This already exists and is starting to gain popularity for new builds. It’s also not that expensive to retrofit, but is most effective when a home is sealed well.