I used an inline fan from an old air-hockey table, with 4" ducting pumping air up through the ceiling to a sealed 3x4x5 box in attic(left it on 24/7, was pretty cold in spring! then HOT.), kept temps btw 68-80 and didn't need an exhaust fan, the box stayed pressurized (when door was closed)and was forced out a right-angle exhaust port, had one adapted PC fan for movement in side box, worked pretty well.