Power Attic Fan
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An electric or solar-powered exhaust fan mounted on the roof or gable that pulls hot air out of the attic; effective only with matching intake, and a source of leaks when the roof-mounted kind is poorly flashed.
What Is Power Attic Fan?
A power attic ventilator is a motorized exhaust fan, usually with a thermostat, that moves far more air than a passive vent. Roof-mounted units sit in a flashed dome; gable-mounted units sit behind a louver. Two things decide whether one helps. First, intake: a fan without enough soffit intake depressurizes the attic and pulls air from the living space through every gap in the ceiling, raising cooling bills. Second, the flashing: a roof-mounted fan is a large penetration, and the dome's flange has to be shingled in like any other roof penetration, not surface-mounted and caulked. Solar-powered units remove the wiring and the operating cost and run when the sun, and the attic heat, are highest; their airflow is lower than a wired unit. A power fan is not a substitute for a balanced ridge-and-soffit system on a new roof; it is a retrofit for attics that cannot be vented passively.
Important Distinction
Note: This describes the component in general. Which product, gauge or detail a specific roof needs is a job-by-job determination made after an inspection, and the building code and the manufacturer's installation instructions govern over any general description.
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Also Known As
These are the search terms and phrases that commonly refer to this topic, so you can find it however you describe it.
Related roofing topics
A power fan without intake pulls conditioned air from the house.
A roof-mounted fan is a large penetration; surface-mounted and caulked flanges leak.
Solar units are the unwired form of the power attic fan.
Questions about Power Attic Fan?
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