Attic Fans are Not the Answer for Hot Upper Floors.

 As Northern VA heats up this summer people start to look for solutions to make there upper floor cooler in the summer. They go to Costco and hear about attic fans and how this magic device will be the miracle cure. First, I want to start by saying that yes, an attic fan will make you feel cooler on the upper floor. There are a lot of people who swear by attic fans. But at what expense is this a solution? 

Let's start with the natural phenomenon of the stack effect. This happens in every structure that is built. The higher it is the more intensified it will be. For every cubic foot of air you leak out the top of this structure another cubic foot comes in at the very bottom.  To simplify, imagine a cubic foot of air to be the size of a basketball. So for every basketball that leaks out the top another one leaks in at the bottom. This is happening naturally all the time.  Now you install an attic fan in the roof of your house. This is now powered stack effect that is making it happen a lot faster. So all that conditioned air your paid to keep your house cool is sucked out into the attic which is outside. You feel cooler because its pulling all the way from your cooler crawlspace or basement. Now your introducing hot humid air into your basement or crawlspace. What does hot humid air do to these areas. It grows mold, it causes ductwork to condensate like a glass of ice tea sitting outside on a hot humid day. It makes your portable dehumidifier run longer running up your electric bill. Also, it fills up its internal bucket and shuts down until somebody will dump it making it not very effective. 

We run several calls for duct sweating in the summer here. Most of them sometimes have to do with having attic fans running or just installed by there roofer. For more information go to a third party website from Energy Vanguard. The articles written by a building scientist call why Attic power ventilators don't help or Why Attic fans suck.