I had an energy audit done recently and one of the recommendations was to air seal and reinsulate the attic which was expected. What I did not expect was the recommendation to install a bathroom fan which would provide the equivalent of constant 20 CFM air exchange. In effect the fan would counteract some of the air sealing efforts which feels very counterintuitive, as in the winter it will suck more cold air in.
The house is 1600 sq ft and the blower door test was 2810 CFM50. The estimate after air sealing is 2248 CFM50. I understand that houses need to get fresh air but 2248 still seems high.
edit: Thanks for the feedback. To provide a little more detail, no I don't currently have a bathroom fan. The fan to be installed would be 110CFM but it would be controlled by a SmartExhaust switch which would be set to run a 20 minutes per hour, as well as come on when the light is on. It claims to be ASHRAE 62.2 compliant which I believe is the standard they are trying to meet.
Best Answer
I agree with Ed, bathroom fans are turned on intermittently to exhaust MOISTURE not to INTRODUCE fresh air into your house, especially on a continual non-controlled (no thermostat or no humidistat) manner. Even outside air intakes on furnaces only work when the thermostat is calling for heat or air conditioning and it usually has a manual damper that you can adjust for the amount of air desired.