Why is my attic fan so loud?
Short answer. A loud attic fan usually has worn motor bearings, which grind or squeal, a blade that is bent, loose or unbalanced, which causes wobble and rattling, or loose mounting screws and a dome that vibrates. Debris or a nest touching the blade, and air roaring through gaps because intake is too small, can also make noise.
Match the sound to the cause
- Grinding or squealing: worn bearings. Many sealed motors cannot be oiled, so the motor or the whole fan needs replacing.
- Rhythmic thumping or wobble: a bent blade, a blade that slipped on its shaft, or a missing balance clip. Tighten the set screw or replace the blade.
- Rattling: loose screws on the motor mount, shroud or dome, or a loose screen.
- Ticking or scraping: debris or a nest touching the blade, or the blade rubbing the shroud.
- Loud hum with little airflow: the motor is straining, often from a failing capacitor or seized bearings.
- Whistling or roaring: the fan is starving for air because intake is too small and is pulling hard through gaps.
What you can check yourself
With the power off at the breaker, in the cool of the morning, look at the fan from the attic side. Spin the blade by hand: it should turn smoothly and quietly with no wobble. Tighten the mounting screws and the blade's set screw. Remove nests, which also invite wasps into the attic. Make sure the housing is not touching rafters or ducts that carry vibration into the house.
When noise means it is time
Fans in hot attics can run many hours a day through a Georgia summer, so motors wear out. If the motor is going, compare the cost of a new motor with removing the fan and improving passive ventilation. Without enough intake, even a new fan will be loud. See roof ventilation basics and attic heat and shingles.