It is going to depend on the type of motor used in the fan.
Don't try a light "dimmer". They are not designed for motor control.
Is it direct drive, or belt driven? If belt driven, you could change pulley
sizes to change the speed.
Every AC motor that would be used in a gable fan that I have ever seen
is fixed speed and determined by the freq of the AC source driving
it. You can't slow it down by lowering the voltage with a rheostat,
which wouldn't be very good idea to begin with. You;d just be
dissipating energy as heat.
Either get a quiet new fan or maybe switch to a passive ridge vent
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.