What is a ridge vent system on a roof, and what does it include?
Short answer. A ridge vent system is more than the vent on the peak: it includes the slot cut in the deck, the vent with its filter and baffle, the cap shingles over it, the soffit or edge intake that feeds it, the baffles that keep insulation out of the airflow, and the removal of competing exhaust vents. If any part is missing, the system underperforms.
The parts
- Ridge slot: cut to the specified width along the peak.
- Ridge vent: rigid or rolled, filtered, ideally with an external baffle, rated for a specific net free area per foot.
- Hip and ridge cap shingles: nailed through the vent.
- Intake: continuous soffit vents, individual soffit vents or edge intake vents.
- Baffles: chutes stapled between rafters above the exterior walls so insulation does not block intake.
- Closed competing vents: box vents, turbines and power fans removed and decked over, and gable vents usually blocked from inside.
Converting from box vents during a reroof
Switching to a ridge vent system is common during a replacement. The crew removes the old box vents, installs new decking in those holes, cuts the ridge slot and verifies intake. On the estimate, expect line items for ridge vent by the linear foot, removal of the old vents, decking by the sheet and any soffit vent additions.
Sizing the system
The system is sized from the attic floor area. At the code's balanced ratio of 1/300, an 1,800 square foot attic needs about 864 square inches in total, so about 432 square inches each of intake and exhaust. At 18 square inches per foot, that is 24 feet of vented ridge, plus at least the same net free area of intake.
Read ridge vent vs box vents and what to expect on roof replacement day.