When you are deciding between a ridge vent or an attic fan consider the needs of the attic.
Roof ridge vents and attic fans.
A fan may actually suck air conditioned air from your home into 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.
Choosing a ridge vent or an attic fan.
Both attic fans and roof vents offer a means of exhausting stale air.
Unlike ridge vents attic fans use electricity and need regular maintenance to keep working properly.
The ventilation that controls moisture from condensation and regulates the temperature in your attic relies on air circulation.
If you have few vents in your attic most of the air will be drawn from inside the house.
In a properly designed passive system air enters through the soffit.
An attic fan is an active system that actually forces air out.
Ridge vents are a passive system simply allowing hot air to rise up through them rather than pushing it out as a fan does.
Both also require other vents that bring air into the attic from outside to replace the volume being expelled.