How does a ridge vent work, and do ridge vents work?
The parts of a ridge vent
- The slot: a gap cut through the decking on each side of the peak, stopping short of the ends of the ridge.
- The vent body: rigid plastic or rolled material that spans the slot and supports the cap shingles above it.
- Openings and filter: louvers or mesh along the sides that let air out and keep insects and blowing rain out.
- External baffle: a raised edge that deflects wind up over the vent.
- Cap shingles: nailed on top so the vent blends into the roof line.
How air moves through it
Hot air collects at the top of the attic and rises through the slot. When wind blows across the roof, the baffle forces it up and over the vent, creating lower pressure right at the openings, which draws attic air out. As air leaves, fresh air enters through the soffits, so the whole underside of the deck gets washed by moving air.
Why it needs intake
A ridge vent does not create airflow by itself. If soffits are blocked, little air moves, or the attic pulls air from the house. If other exhaust vents are on the same attic, the ridge vent may draw air from them instead of the soffits. Balanced intake is what makes a ridge vent effective.
Signs it is working
Daylight visible through the slot from the attic, a dry deck with no mildew near the peak, and no rust on nail tips are all good signs. See ridge vent vs box vents and roof ventilation basics.