What is the air vent on top of my roof, and how can I tell which kind it is?
Short answer. Most air vents on top of a roof are attic exhaust vents: a ridge vent along the peak, box vents near the top of the slopes, a spinning turbine, or a powered fan dome. Narrow pipes with collars are plumbing vents and metal hoods with flaps are exhaust caps, and neither counts as attic ventilation.
Identify it from the yard
- A slightly raised line along the peak: a shingle-over ridge vent. The cap shingles sit a little higher than a solid ridge, and you may see a thin dark gap at each end.
- Square or rounded hoods near the top of a slope: static box vents, often called turtle or louver vents. Most homes with them have several in a row.
- A spinning metal globe: a wind turbine, sometimes called a whirlybird, which turns in the wind and draws air out of the attic.
- A larger, low dome, sometimes with a small solar panel: a powered attic fan run by a thermostat.
- A narrow pipe with a rubber or metal collar: a plumbing vent stack that lets the drain lines breathe.
- A metal hood with a flap: an exhaust cap for a bath fan or range hood.
Why the type matters
Attic exhaust vents work best when they are all one kind. A ridge vent sharing the roof with box vents or a turbine can pull air from the nearest high opening instead of from the soffits, leaving part of the attic stagnant. Plumbing stacks and exhaust caps are separate systems, so they should never be counted when you tally attic ventilation.
What to check on it
- Dents or cracks after hail. Damaged vents are often the first clue that a storm hit the shingles too.
- A turbine that wobbles, squeals or has stopped spinning.
- Missing or lifted cap shingles over a ridge vent after high wind.
- Rust streaks or cracked sealant around the base, which can leak.
For how these vents fit together, see roof ventilation basics and ridge vent vs box vents.