Always remember that any air out of the house has to be made up with exterior air, depending where you live this can mean that you are pulling in hotter air or a higher humidity, let alone any allergens in the air. I have two fans in my closet but also have a much higher heat load with some servers. Fan one, ac infinity, pulls air and recycles it into the return side of the air handler. This allows the heat to be spread across the entire house when the ac is off and pulled through and cooled when the ac is on, in these Texas summers the ac isn't off much. For fan two it is on a temperature relay that only comes on if the temp reaches 100 in the closet which I have had happen a few times with all servers on, this just dumps the hot air outside but again is only in the extreme and non-normal condition. The AC Infinity fans are good but make sure you test it upon delivery, I had the first one that I ordered come with the blower out of balance causing quite a bit of excess noise at higher speeds.