ridge vent
A vent located at the ridge of the roof that allows the escape of warm and/or moist air from the attic area or rafter cavity; it is usually a simple shielded gap but may be a ventilator (device).
ridge vent: continuous attic exhaust at the roof peak
A ridge vent is an opening that runs along the peak where two roof slopes meet, sized to let warm and humid air escape from the attic cavity. It works as part of a passive ventilation system, paired with soffit intake vents lower on the eaves; air enters at the soffit, rises through the rafter bays heated by the roof deck, and exits at the ridge without requiring fans or moving parts.
The simplest ridge vent is a shielded slot cut into the roof sheathing and sealed with metal cap flashing that covers the opening while letting air pass out underneath. More sophisticated versions use a raised profile cap with internal baffles or screens to prevent rain intrusion while maintaining airflow. Most ridge vents are rated to allow 1 to 1.5 square inches of net free area per linear foot of roof length, though actual performance depends on cap design and installation quality.
How it fits the ventilation strategy
Building codes generally require continuous soffit-to-ridge ventilation in pitched roof attics to control moisture and temperature. A ridge vent sized correctly (typically one inch of opening per eight to ten inches of roof length) promotes natural convection: the combination of wind pressure differences and the stack effect of rising warm air draws moisture out year-round. Without it, condensation accumulates on roof framing and sheathing in cold seasons, rotting wood and enabling mold.
Installation errors are common and costly. Poor flashing allows water penetration around the vent opening. Incomplete blocking removal in attic partitions prevents air circulation across the width of the roof. Blown-in insulation pushed up into soffit vents blocks intake air, defeating the entire system. A ridge vent cannot function if the corresponding soffit vents are obstructed or absent.
The term "ridge vent" is sometimes used loosely to include ridge cap ventilators, which are boxed units with moving louvers or turbines. Those are distinct from the fixed shielded slot vents more commonly installed today, which are quieter and simpler but depend entirely on natural airflow. Building inspectors frequently check ridge vent alignment and condition as part of roof system verification.