Attic Ventilation Fans

By Robert Robillard on Energy Saving

Attic Ventilation FansPhoto source:

Are Attic Fans worth installing?

I’m not a big fan of attic ventilation fans.   Attic ventilation fans are usually mounted in the upper slope of the roof and are designed to cool the attic, save energy on cooling costs and extend the life of the roof shingles. These thermostatically controlled bfans push out the “upper” attic hot air and drawing in cooler outside air, usually through the lower soffit vents.

The unmentioned evil of  attic ventilation fans is that they often pull interior, air-conditioned air up from the home into the attic through small cracks in the ceiling.  [wires, pipes and other air leak penetrations]  Once this happens negative pressure that is created in the house pulls hot outside air into the house, causing the air conditioner to work longer.

I’ve also heard that attic ventilation fans can cause back draft issues with gas appliances [e.g. water heater] which can cause health and safety problems. The fan basically causes make-up air to come down the flues rather than from the passive attic vents.  This often results in a water heater or boiler not venting flue gasses properly, and the fumes actually being vented to the inside of the house. I’d consult your plumber or appliance HVAC technician on this one.

Because of the “negative pressure” inside the house that attic ventilation fans create, I don’t feel that they save you money on electricity or cooling costs.

Let’s assume that you have a super tight house and no leakage, there are solar powered fans on the market that draw no electricity.  Solar attic ventilation fans cost you nothing to operate, but you still have the negative pressure issue.   Additionally, the cost to purchase and install one will take you a decade or more to recover the energy savings.   I would only consider a solar powered fan if you were going to be re-roofing and already had a reason to be on the roof.

If you’re not re-roofing and have gas appliances, susceptible to a back draft, my advice is to allow passive ventilation to do its job through natural convection [upward flow of heat through soffit, eve and ridge venting.

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About the author

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzz As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising the bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob

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