You guys are forgetting minimum oxygen levels and at the same time, maximum CO2 levels... this is what brings on the 'stuffiness' sensation. In fact, I have seen technical specifications on commercial ventilating systems that have CO2 sensors that control the duty cycle of the air-exchange systems.
I don't think that there would be that much heat that would be lost in .35 ACH, (in your case 67,000 cu ft), especially when you consider that 5 to 7 ACH was considered acceptable a few years ago, which would be 7 to 20 times as much heat lost.
My house is approaching the stuffiness level. I had to work pretty hard to get there, too. I'm looking for, or will build a small .35 ACH high efficiency HRV, myself. I'm figuring that if I have a crowd of people in the house who are active or dancing, I can open windows to make up the difference.
-AC
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I'm not an HVAC technician. In fact, I'm barely even a hacker...
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