Both attic fans and roof vents offer a means of exhausting stale air.
Roof ridge vents and attic fans.
In a properly designed passive system air enters through the soffit.
By installing more roof vents such as a ridge vent you increase the possibility that most attic air will come from outside says tim carter a residential contractor in cincinnati.
The ventilation that controls moisture from condensation and regulates the temperature in your attic relies on air circulation.
An attic fan is an active system that actually forces air out.
Choosing a ridge vent or an attic fan.
Both also require other vents that bring air into the attic from outside to replace the volume being expelled.
A fan may actually suck air conditioned air from your home into the attic.
When you are deciding between a ridge vent or an attic fan consider the needs of the attic.
Help protect your roof system from premature deterioration by installing a properly balanced attic ventilation system consisting of cobra exhaust vent at the ridge and adequate intake ventilation at or near the soffit areas of your roof.
While a power vent fan combined with a ridge vent can work against the natural flow of air through the attic it will still exhaust more hot air than not having a fan at all it s just not the most efficient way to go about it.
If you have few vents in your attic most of the air will be drawn from inside the house.