How can you tell if your attic is vented at all?
Short answer. Look for intake vents under the eaves and exhaust vents on the roof or gable walls; if you find both and the attic floor is insulated, the attic is vented. If foam insulation is sprayed on the underside of the roof deck and the vents are sealed, it is an intentionally unvented attic; if there is no foam and you find no vents at all, the attic is unvented by accident, which is a problem.
Signs of a vented attic
- Perforated soffit panels, strip vents or rectangular undereave vents.
- A ridge vent, box vents, turbines, a fan or gable louvers.
- Insulation on the attic floor, with the deck above bare.
- Daylight visible at the eaves or the ridge from inside.
Signs of an intentionally unvented attic
- Spray foam covering the underside of the roof deck and the gable walls.
- No vents on the roof over that area, and sealed soffits.
- An attic that feels close to house temperature, often with the air handler and ducts inside it.
These are built under the code's unvented attic rules and are fine when done right.
Signs of an accidentally unvented attic
- Fiberglass or cellulose on the attic floor, bare deck above, but no working intake or exhaust.
- Gable louvers painted or boarded shut.
- Vented soffit panels installed over solid plywood with no holes.
- Old box vents removed during a past reroof and never replaced.
Accidentally unvented attics trap heat and moisture against the deck. Look for dark staining, rusty nails and damp insulation.
Why it matters before a reroof
The roof design depends on which type you have: a vented attic needs balanced intake and exhaust, while an unvented attic needs the vents left closed. See roof ventilation basics and attic heat and shingles.