How to ventilate an attic

[Bart K]

I replaced my roof last year and the roofers put in ridge vents (my request).

I have four gable vents and two roof fans. My home is about 60 years old and there are no soffit vents.

The previous owner(s) had no roof vents but depended on the gable vents.

Question: Should I close the gable vents and turn off the fans? Putting soffit vents in is out of the question. The attic is well insulated. Blown in, and seems cool in summer heat.

[home improvement guy]

From your description it appears you have separate rooflines because you added more than one ridge vent. Your attic is now improperly over-ventilated. The gable vents do not need the fans, which simply localize air movement and increase energy usage. Two fans are not better than one for a single attic space.

When a home has separate attic spaces, the fans simply move warm, moist air to a limited area near the fan. Areas of the attics that are further away from the fans will have little to no air movement. By adding ridge vents, the fans are now pulling air from the sections of the ridge vent that are closer to the fans. When the fans are operating, they can pull rain into the attic through the ridge vent and, if not thermostatically controlled, they could even pull snow through the ridge vent.

Without soffit vents, the lower attic areas where the rafters are close to the ceiling joists are not being properly vented. If you do not want to install soffit vents or if there is no overhang to the roof design, there are products available such as Cor-A-Vent's In-Vent that is installed on the surface of the roof providing adequate ventilation for the ridge vent. Having a properly balanced venting system is important to the life expectancy of the shingles and to the attic's environment. My advice would be to seal or remove the fans, seal the gable vents and install the In-Vent or a similar roof/attic venting system.