Do I need a bathroom fan to increase house ventilation?
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.