Attic Fans SUCK! Really... both literally and figuratively

As we enter the cooling season and temperatures start rising outside , we often get asked by our clients about installing attic fans or fixing their old one that has never really worked.

Using an attic fan to lower those extremely hot temperatures in your attic to make the house easier to cool is logical, especially if you listen to the gimmicky marketing at Home Depot/Lowes or countless contractors that are not applying principles of building science. The truth is, attic fans SUCK, both literally & figuratively! Lets explore what really happens with attic fans and why you should almost never install one in your home!

The theory is, on a hot summer day, the fan is supposed to remove hot air from the attic by exhausting it out, then replace it with cooler air from outside, saving you energy & money? What really occurs is your attic fan turns on creating a pressure differential between your attic and your conditioned home. It then pulls air from the path of least resistance, some coming from the gables & soffits, but most coming from inside your home through the top plate (ceiling/attic floor). Therefore, you are air conditioning your attic because the attic fan is truly SUCKING the air conditioning right out of your house. In most houses the top plate may have a good layer of blown or batt insulation. While the insulation provides a good thermal barrier, it does not create an adequete air or vapor barrier, especially with an attic fan creating pressure differentials between the spaces influencing air movement. Unless you have spray foam insulated your entire attic floor, an attic fan is going to do more harm than good. In addition to energy loss, there are a variety of other negative issues that attic fans can cause such as air quality and combustion safety issues.

So, attic fans (along w/replacement windows) fall into the category of well marketed energy saving products that simply don’t live up to the hype when applying sound building science and objectively derived data from comprehensive Home Energy Audits, all leading to the conclusion that attic fans truly SUCK!  That is why our Energy Auditors  never recommend them to our clients.

energyMusings is written by Sean Schmidt, President of Holistic Home Energy Services, an Energy Auditing & Home Performance Contractor in Maryland. In addition to being a certified Building Analyst and Envelope Specialist, Sean has been in the HVACR field for 20 years. He is currently the President of Heating & Air Conditioning Contractors of Maryland, sits on the Board of the Maryland Alliance for Fair Competition (MAFC) and is an active member of Efficiency First.

To learn more about Sean and Holistic Home, visit their website, as well as their pages on Facebook, Twitter, LinkedIn and this blog.