Keep in mind that these powerful fans have their drawbacks. In houses with gas- or oil-fired combustion appliances, there is a danger that a fan will pull flue gases out of a chimney and back into the house. Problems like this can occur in houses that are relatively air-tight. Before you recommend installing one of these fans, talk to your HVAC contractor about the dangers of flue gases getting into the house. Another danger is that the fan will pull humid air from a moldy basement or toxic air from a garage into the house, especially if not enough windows are opened when the fan is running. Make sure to weatherstrip basement and garage doors, including using threshold sweeps.
