What is an attic fan?
Short answer. An attic fan usually means a powered attic ventilator: a thermostat controlled fan mounted on the roof or behind a gable vent that pushes hot air out of the attic. It is different from a whole house fan, which sits in a hallway ceiling and pulls cooler outdoor air through open windows into the house and out through the attic.
Types
- Roof mounted powered attic ventilator: a dome over a fan, wired to a thermostat that switches it on at a set attic temperature.
- Gable mounted fan: installed behind a gable vent to do the same job.
- Solar attic fan: runs from its own small solar panel with no wiring.
- Whole house fan: a large fan in the ceiling of the living space, used on cool evenings to flush the house with outdoor air. It needs generous attic vent area to exhaust into.
How to use one well
- Set the thermostat high, often somewhere around 100 to 110 degrees, so the fan does not run constantly.
- Make sure the intake vents can supply the air the fan moves.
- Air seal the ceiling so the fan does not pull conditioned air from the house.
- Do not run it alongside a ridge vent.
- Look for a model with a high temperature safety cutoff.
Is one right for you?
For most homes with good soffit intake, passive ventilation is enough, and it has nothing to wear out. A fan can help where passive exhaust is not possible, but insulation and air sealing usually do more for comfort. Read attic heat and shingles and ridge vent vs box vents.