I can second this. For a brief period of time, I rented a house with a filtered HVAC system (rare in EU). The system was continuously pumping in fresh air from

I can second this. For a brief period of time, I rented a house with a filtered HVAC system (rare in EU). The system was continuously pumping in fresh air from the surroundings, a nice little forest. I felt really fresh, especially in the morning, after years of sluggishness. I began measuring CO2, and it was way lower than my current property unless I open the windows really often. This is not practical without a heat recovery system.