Are ridge vents better than roof vents like box vents?
Short answer. For most gable roofs, a ridge vent is better than a row of box roof vents because it exhausts from the very top, vents every rafter bay evenly, and needs fewer holes in the roof. Box vents are the better fit on hip roofs with short ridges, where there is not enough ridge length to provide the exhaust the attic needs.
How they compare
- Airflow pattern: A ridge vent pulls from the whole length of the peak. Box vents pull from spots a few feet below it, so air above and between them can stagnate.
- Capacity: Many shingle-over ridge vents are rated somewhere around 12 to 18 square inches of net free area per linear foot, so 30 feet of ridge can supply several hundred square inches. A common box vent provides roughly 50 to 60 square inches, so it takes a row of them to match. Check the label on any product, since ratings vary.
- Leak points: Each box vent is a separate hole with its own flashing. A ridge vent is one continuous detail at the peak, covered by cap shingles.
- Hail: Plastic box vent hoods crack in Georgia hailstorms more readily than shingle covered ridge vents, and cracked hoods leak.
- Looks: A ridge vent nearly disappears; box vents are visible, especially on the street side.
When box vents make more sense
On hip roofs, the ridge can be only a few feet long. The code path that allows the reduced 1/300 ventilation ratio wants 40 to 50 percent of the required area high in the attic, within 3 feet of the ridge measured vertically, and a short ridge may not provide it. Box vents placed high on the slopes, sometimes combined with hip vents, can close that gap.
Do not mix them
Whichever you choose, use one type of exhaust per attic. A ridge vent plus box vents on the same attic tends to short circuit, with air entering one exhaust and leaving through the other instead of coming in at the soffits. See the full comparison in ridge vent vs box vents.