The net free vent area nfva shall not be less than 1 150 of the area of the space being vented.
Roof venting requirements.
Ft or more of unobstructed roof venting also known at 2 7 sq.
Of vent for every 300 sq.
Building codes vary.
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.
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.
When exhausted directly outside.
Roof vents choose one of the following products to meet the recommended exhaust nfva of 528 square inches.
Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.
Before we explore how to ventilate an attic space it is prudent to understand how much ventilation is needed.
Theinternational building code 2012 edition ibc 2012 requires enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof framing to have cross ventilation for each separate space.
Most building codes require a ratio of 1 150 ventilation space to attic floor space.
If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation.
Ft of net free venting.
Measure the length and width of the attic floor space to be ventilated.
The key to proper ventilation of your roof and attic is balance.
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.
According to their requirements you should have 1 square foot of attic ventilation per 300 sq ft of attic floor space.
Ventilation can be accomplished using various products and techniques.
Section r806 roof ventilation 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.
There should also be a 50 50 balance of attic venting and roof venting.
