Ventilation component
What is a ridge vent?
A slot cut along the peak of the roof, covered by a low vent and capped with shingles, that turns the whole attic into a chimney — provided the soffits can feed it.
Updated September 12, 2026 · Every figure links to its source · Sources
DefinitionComponentAlso called: continuous ridge vent
Ridge vent — a continuous ventilator installed along the ridge of a sloped roof over a slot cut through the sheathing on each side of the peak, covered by ridge-cap shingles, through which attic air exhausts at the roof's highest point; it is the usual way of providing the upper-attic vent area the 2021 IRC, Section R806 describes, and the NRCA glossary lists it among ridge ventilators.
What it is
Warm air rises. In an attic it collects at the ridge, and a vent there lets it out; the air it displaces is drawn in at the lowest point, the soffit. A ridge vent is a low profile of moulded plastic or a corrugated mat, a few inches wide and the length of the ridge, set over a slot cut an inch or so wide on each side of the peak, then covered with cap shingles so that from the ground it reads as a slightly thicker ridge. Baffles on the vent keep rain and snow out and, on the better types, use passing wind to pull air out.
The code sets the area, not the device. The IRC, Section R806.2 requires net free vent area of at least one 150th of the attic floor area, reduced to one 300th where 40 to 50 percent of it is high in the attic, at least three feet above the eave vents, with the balance at the eaves — the arrangement a ridge-and-soffit system is built to satisfy. The directory's roof ventilation calculator does the arithmetic for a given attic and vent product.
Why it matters
Ventilation is what keeps a roof deck dry from below and a shingle roof from cooking from underneath; it is also half of the cure for ice dams, because it keeps the deck as cold as the eave. A ridge vent does this along the whole length of the roof rather than at a few box vents, with nothing to fail and no power. It only works, though, if the intake exists: a ridge vent over blocked or absent soffit vents draws air from wherever it can — around the vent itself, or from the house through ceiling gaps — and does little for the attic. Insulation baffles at the eaves, required by Section R806.3 where eave vents are used, are what keep the intake open.
A common mistake is adding a ridge vent to a roof that already has gable vents or power fans and leaving them in place, which short-circuits the flow. The directory's how-to on installing a ridge vent covers the slot, the vent and the cap, and the question of what to close.
What it costs and who does it
Priced by the linear foot of ridge, including the slot, the vent and the cap shingles, a ridge vent is a modest line on a re-roof and the natural time to add one; retrofitting on an existing roof adds the labour of removing and replacing the existing ridge cap. Roofing contractors do the work; adding soffit vents and baffles to feed it may be a separate line or a separate trade. The directory's roof repair cost guide explains how such items are priced.
Frequently asked questions
Short answers; the sections above carry the detail and the sources.
Do ridge vents work without soffit vents?
How much ridge vent do I need?
Can a ridge vent leak?
Next step
Find a roofer who does this
A ridge vent is only as good as the soffits below it, and a good roofer looks at both. 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)