I haven't used a fan. Last year I had a styro cooler setup; this year, a wine cooler fridge. I have the FWatt going completely from the floor to top of the inside of the incubator (about 2.5 feet high) and I took different readings of the temps and things are evened-out. I use closed pop bottles of water to store heat in areas where there are no tubs. I like to keep with what works and would be leary of changing things now. This is definately something that has to be thought out before eggs arrive!