Should you close gable vents when you have a ridge vent, and how?
Short answer. In most attics, yes: open gable vents sit high, so a ridge vent pulls air from them instead of the soffits and the lower attic stays stagnant. The usual fix is to block the gable louvers from inside the attic with rigid foam or plywood, leaving the louver on the outside for appearance, as long as the attic has adequate soffit intake.
Why they conflict
Air takes the shortest, easiest path. With a ridge vent at the peak and gable louvers near the peak at each end, air flows in one gable and out the ridge, or in one gable and out the other, bypassing the eaves. The lower deck, where moisture collects, gets little airflow.
How to close them
- From inside the attic, measure the opening behind each louver.
- Cut rigid foam board or exterior plywood to fit snugly in the framed opening.
- Seal the edges with foam or caulk.
- Leave the exterior louver in place so the house looks the same.
- Check the louver's screen from outside so wasps and birds do not nest between the louver and the panel.
The work is reversible, which helps if a future owner changes the ventilation design.
Exceptions
- No usable soffit intake: if there is no intake and none can be added, closing the gables may leave the ridge vent starved. Better to add edge intake.
- A gable louver serving a separate attic space the ridge vent does not reach.
- Gable fans: these conflict with a ridge vent even more and should be disconnected.
Do the math
With gables closed, confirm soffit intake equals or exceeds the ridge vent's net free area. See ridge vent vs box vents and roof ventilation basics.