yeah, but if you have a forced hot air heat system, and you hook up to the return ducts, which is pulling air from inside your house INTO the furnace, you'll have negative pressure from the furnace blower when the heat is on, but, when the heat isn't on, you won't have negative pressure. So, your fan will have to deal with that. The right way to do it would be to have your fan ON when the heater/ac is OFF, and the fan OFF when the heater/ac is ON. knowwhatimsayin? youd have to hook up a relay for that. might work without it though but might burn up your fan