It's actually pretty minimal- I live in a mild climate, and even doing this sometimes I probably spend under $50/year on home heating and leave the windows cracked most of the time.
My home was most likely 'retrofit' in the '90s to make it airtight for efficiency, and even with the windows cracked is too airtight to be healthy, and still more so than it was probably designed for in the ~1950s.
My home was most likely 'retrofit' in the '90s to make it airtight for efficiency, and even with the windows cracked is too airtight to be healthy, and still more so than it was probably designed for in the ~1950s.