ROOF VENTILATION

Philadelphia Code Subcode R, § R806

in effect

SECTION R806 ROOF VENTILATION [Pursuant to the UCC, delete Section R806.1 and replace as follows:] R-R806.1 Ventilation required. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Ventilation openings shall have a least dimension of 1/16 inch (1.6 mm) minimum and 1/4-inch (6.4 mm) maximum. Ventilation openings having a least dimension larger than 1/4 inch (6.4 mm) shall be provided with corrosion-resistant wire cloth screening, hardware cloth, perforated vinyl or similar material with openings having a least dimension of 1/16 inch (1.6 mm) minimum and 1/4-inch (6.4 mm) maximum. Openings in roof framing members shall conform to the requirements of Section R802.7. Required ventilation openings shall open directly to the outside air. [Pursuant to the UCC, delete Section R806.2 and replace as follows:] R-R806.2 Minimum vent area. The minimum net free ventilating area shall be 1/150 of the area of the vented space. Exception: The minimum net free ventilation area shall be 1/300 of the vented space provided one or more of the following conditions are met: 1. In Climate Zones 6, 7 and 8, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling. 2. Not less than 40 percent and not more than 50 percent of the required ventilating area is provided by ventilators located in the upper portion of the attic or rafter space. Upper ventilators shall be located not more than 3 feet (914 mm) below the ridge or highest point of the space, measured vertically, with the balance of the required ventilation provided by eave or cornice vents. Where the location of wall or roof framing members conflicts with the installation of upper ventilators, installation more than 3 feet (914 mm) below the ridge or highest point of the space shall be permitted. [Pursuant to the UCC, delete Section R806.3 and replace as follows:] R-R806.3 Vent and insulation clearance. Where eave or cornice vents are installed, nothing shall not block the free flow of air. Not less than a 1-inch (25 mm) space shall be provided between the insulation and the roof sheathing and at the location of the vent. * * *

Source: City of Philadelphia, The Philadelphia Code and Home Rule Charter (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/philadelphia/latest/philadelphia_pa/0-0-0-312046Fetched: 10/27/2026