All you got to do with that fan is to circulate the air. Do you have a T-stat on your exhaust fan? I point my fan at the tops of the plants,it's mounted on the wall. I have a tempstat that turns my exhaust fan on and off,when reaching the temp I have it set to come on.Get a smaller fan with a high/low switch on it at wal-mart for around 10 bucks.

Ga Grown!