Article by Laura Fisher Kaiser
Power up your attic ventilation
Power-assisted roof vents work even in still air and ensure vigorous ventilation. They relieve heat buildup in the attic, where temperatures can reach 150 degrees or more in summer. Reducing attic heat buildup prevents trapped, hot air from warming ceilings and radiating back into your living areas–a problem that also is avoided with proper attic insulation.
Mount power-assisted roof vents near the roof peak on the back slope of the roof, where they are less visible from the street, or high on a gable end wall.
Typically, a single power-assisted roof vent will service an average-sized home.
Costs for power-assisted roof vents
Power-assisted roof vents cost between $70 and $300, plus labor to install, and $2 or $3 a month to operate. For another $90 to $150, you can include an optional humidistat and thermostat, which turn on the fan when excessive humidity and/or temperatures are detected inside your attic space.
If your attic lacks electrical wiring, it may be necessary to have a licensed electrician run a circuit or line extension to power the fan. Depending on the complexity of the project, figure on paying $50 to $100 per hour for a job that may take 2 to 4 hours.
Solar-powered roof vents have zero operating costs and sell for $350 to $600. Some are eligible for state tax incentives and local utility rebates.
Some builders complain that solar-powered roof vents may not work properly when it’s cloudy, and that these types of vents don’t pull enough air.
Drawbacks of power-assisted roof vents
While roof vents definitely remove hot air from attics, their effect on air conditioning needs is disputed.
Some experts believe that because power-assisted roof vents evacuate hot air, they create negative pressures inside the home, drawing in hot outside air and increasing the load on existing air conditioning systems. However, this potential problem typically is avoided with the addition of adequate soffit vents, which allow fresh air into the attic.
Another concern is that a roof vent adds another penetration through roofing materials, and that the vibrations caused by the motorized fan made lead to the failure of caulks and sealants, increasing the risk of water leaks.
Laura Fisher Kaiser is a contributing editor at Interior Design magazine, a former editor of This Old House, and writes the blog Secret Science Geek. She lives in Washington, DC.