Roof Ventilation Requirements

Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge.

Roof ventilation requirements.

You can calculate attic ventilation requirements by determining the square footage of your attic floor its width times its length and compare that to the total required net free area nfa. 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. Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space. Measure the length and width of the attic floor space to be ventilated.

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. Feet of attic space divided 50 50 between the inlets and outlets. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca. The net free vent area nfva shall not be less than 1 150 of the area of the space being vented.

Ventsure 4 foot strip heat moisture ridge vent 27 lineal feet required. Industry standard for proper attic ventilation recommends for no vapor retarder type of attic insulation no paper plastic or aluminum layer between the attic floor and insulation layer 1 sq. Blocking and bridging must be arranged so they do not interfere with air movement. Foot of ventilation for every 150 sq.

The key to proper ventilation of your roof and attic is balance. The amount of space you devote to intake must be equal to the amount you allow for exhaust and these must be calculated according to the size of your attic and slope of your roof. Most building codes require a ratio of 1 150 ventilation space to attic floor space. You can also contact your local municipality to check on building code in your area.