> then I read about the NYC's oversized steam powered heater that allowed you to open windows during winter to achieve proper air change per hour during Spanish

> then I read about the NYC's oversized steam powered heater that allowed you to open windows during winter to achieve proper air change per hour during Spanish flu. > I guess what I am saying is don't fight the nature if you can, and architecture it properly. Oversized steam heaters are exactly fighting nature, are they not? Really, every building system is a fight against nature. The idea is to exploit properties of materials and the forces of nature when you can to get closer to whatever your chosen optimum is without having to fight nature so hard. It's not even that hard build to near PassivHaus standards for airtightness these days with regular materials (I did it). It does take an intention to focus on airtightness, which most production builders don't have. > failing that, airtight + mechanical ventilation is going to be expensive and probably impossible to hit good air quality (6ACH+)... 3ACH is plenty for good indoor air quality. I got close to that once with a whole house ventilating fan that cost $300. HRV/ERV are more expensive, but they also do heat recovery and air filtration, and provide consistent air quality everywhere.