Keep Attics Cool with a Power Roof Ventilator

Gene and Katie Hamilton

Gene and Katie Hamilton

Air circulation in the attic is important because on hot days it prevents the space from overheating. When the thermometer drops, proper air flow reduces attic humidity and improves insulation performance.

A contractor will charge $308 to install a 14-inch power ventilator which includes the labor and material; you can do it for more than half and pocket a 57 percent savings. That’s assuming you have carpentry experience and don’t have a steeply pitched roof. If the idea of working on the roof and cutting a hole in it is too intimidating, don’t hesitate to hire out the job.

For about $130 you can buy what you need: a power ventilator, an electrical box and cover, a short piece of three-wire BX or Romex cable, a package of wire nuts and a quart of roofing cement. An electrical circuit is needed to power the fan. If there isn’t one already in the attic, call an electrician.

You’ll need basic carpentry tools, and for cutting the roof opening rent a reciprocating saw. While you’re working on the roof, you’ll need someone inside the attic to help you.

Tip: Check the manufacturer’s recommendations for the amount of intake vents required for the fan to run efficiently. You might have to install additional vents in the eaves or gable ends.

Gable or soffit louvered vents are required as fresh air intakes for powered attic ventilators. The Home Ventilating Institute recommends that a powered attic ventilator should provide at least ten air changes per hour. To determine the proper CFM (cubic feet per minute) rating for a fan which will provide that number of air changes, multiply the total square footage of your attic by .7. To find the total square footage multiply the length of the attic times its width. Let’s say it comes out as 1500 square feet. 1500x.7 = 1050 CFM That means a fan with a 1050 CFM rating is needed.

To compare the cost of doing it yourself and hiring a contractor for hundreds of improvements visit


Gene and Katie Hamilton are authors of 20 home improvement books and creators of, a website that compares the DIY and contractor costs of hundreds of repair, decorating and remodeling projects. Their weekly column Do It Yourself or Not is syndicated by Tribune Content Agency.
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