Ventilation component
What is a gable vent?
The louvered triangle, rectangle or half-round high in the end wall of a house, letting attic air out — and the questions to ask before combining it with a ridge vent.
Updated September 12, 2026 · Every figure links to its source · Sources
DefinitionComponentAlso called: gable louver, gable end vent
Gable vent — a louvered and screened opening set in the gable end wall of a house, near the peak, through which attic air can enter and leave; it is one of the ways of providing the attic ventilation the 2021 IRC, Section R806 requires, and the NRCA glossary lists it among vent types.
What it is
A gable vent is a frame of wood, vinyl or aluminium with angled louvers and an insect screen, set into the gable wall and open to the attic behind it. On a house with vents in both gable ends, wind blowing across the house pushes air in one and out the other — cross-ventilation — and warm air rising in the attic finds its own way out when the air is still. It is the oldest form of attic venting and is often the only one on older houses.
The code does not prescribe a vent type; it prescribes an area. The IRC, Section R806.2 requires a net free ventilating area of at least one 150th of the area of the space ventilated, which can be reduced to one 300th when 40 to 50 percent of it is located in the upper part of the attic — at least three feet above the eave vents — with the balance at the eaves. Gable vents, being high, count toward the upper share.
Why it matters
Attic ventilation carries off the moisture that rises from the house and the heat that builds under the roof in summer; without it, sheathing grows mould on its underside, shingles age faster from below, and in winter the warm attic melts snow into ice dams. A gable vent does that job on its own for a simple attic, and it does it for free — no fan, no power.
The complication is mixing systems. The modern arrangement is intake at the soffit and exhaust at a continuous ridge vent, which uses the whole attic as a chimney. Gable vents open in the middle of that path can let the ridge vent draw its air from the nearby gable opening rather than from the soffits, which leaves the lower attic unventilated — a "short circuit" that ventilation designers and vent manufacturers warn about. Whether to close, keep or add a gable vent depends on the attic's shape and what else is installed; the directory's roof ventilation calculator works out the required area and the directory's entry on installing a ridge vent describes the soffit-and-ridge system it would join.
What it costs and who does it
Installing or replacing a gable vent is a small carpentry job — cut the opening, frame it, set and flash the vent into the siding, screen it — priced per unit and done by a roofing, siding or general contractor; a decorative vent in an unvented attic is a trim item only. Where a gable vent is to be closed as part of a ventilation redesign, the roofer doing the ridge vent usually blocks it from inside. Assessing the whole attic — intake, exhaust, baffles and air-sealing — is the part worth paying for.
Frequently asked questions
Short answers; the sections above carry the detail and the sources.
Do gable vents work with a ridge vent?
How much attic ventilation does the code require?
Should a gable vent be screened?
Next step
Find a roofer who does this
Ventilation is a system, not a part; the right contractor looks at the whole attic before selling a vent. The directory lists roofing contractors by state and city.
Sources
- 2021 International Residential Code, Chapter 8: Roof-Ceiling Construction — International Code Council (ICC)
- Roofing glossary — National Roofing Contractors Association (NRCA)