What is the roof vent on the side of my house?
How to tell what you are looking at
- Gable vent: rectangular, triangular, round or octagonal, with fixed louvers, set in the triangle of siding under the roof peak. It opens straight into the attic.
- Dryer vent: a small hood near the floor line of the laundry room, often with lint around it.
- Bath or kitchen exhaust cap: a hood with a hinged damper flap, usually on an upper wall near that room.
- Foundation or crawl space vent: low on the foundation wall and unrelated to the roof.
What a gable vent does
On older Georgia homes built before ridge vents were common, a pair of gable vents was the whole ventilation system. Wind blows in one end and out the other, which works reasonably when the wind hits the wall squarely and poorly when it does not. When soffit vents are also present, warm air can rise and leave through the gables even on still days.
Should it stay open?
If the roof now has a ridge vent and soffit vents, most roofers and shingle manufacturers recommend blocking the gable vents from the inside. An open gable near a ridge vent becomes a shortcut: air enters the gable and exits the ridge, bypassing the eaves, so the lower roof deck and the insulation near the eaves get little airflow. If the house has gable vents and no soffit intake, the gables may be doing the only useful work, and closing them would be a mistake.
Check the screen behind the louvers while you are looking. A torn gable screen is a favorite entry point for squirrels, birds and bats. See roof ventilation basics for how intake and exhaust pair up.