Best Practices Attic Ventilation

Mark attic roof air vent locations.

Best practices attic ventilation. Cut the hole for roof vents. The international residential code irc provision for attic ventilation requires a ratio of one square foot of net free open ventilation area for every 150 to 300 square feet of attic square footage. The recommended ventilation ratio to provide for vented attic assemblies when an air barrier is present is the 1 300 ratio as specified by most building codes. The average family of four generates 2 to 4 gallons of water vapor a day through activities such as cooking cleaning showering laundry and breathing.

Cut the shingles for roof vents. Hot air exhaust vents located at the peak of the roof allow hot air to escape. Intake vents located at the lowest part of the roof under the eaves allow cool air to enter the attic. 1 300 ventilation ratio recommended.

Drive nails up through the sheathing and. Roof insulation thermal resistance at roof perimeter should be equal or greater to thermal resistance of exterior wall. Experts recommend using attic ventilation in hot climates as part of an overall strategy to reduce cooling loads. Adapted paraphrased with permission from best practices guide to residential construction chapter on best roofing practices.

From the roof s peak. Center nails between rafters 18 in. This configuration also tends to evenly wash the entire underside of the roof surface with ventilation air. For both attics and cathedral ceilings roof ventilation works best when it is balanced between high and low to take advantage of natural convection figure 2 55 at left.

These vents allow outside air to enter the attic at the lowest point of the roof along the underside of the eave. How to install roof vents. Attic ventilation can help remove the water vapor safely.