[Crowbob]

When the time comes to replace my ceiling exhaust fan in the main floor bathroom, I am going with as much CFM as is possible. At night, I can open certain windows and completely replace the air in various zones of the house.

An attic fan does the same for an attic. A low output fan, if the operation cost is minimal (such as solar-powered) will be beneficial because it can run full-time in day-light hours.