Roof Venting Ratio

Near ridge of the roof.

Roof venting ratio.

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. 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. There should also be a 50 50 balance of attic venting and roof venting. In order to find the right calculator divide the attic floor space by 300 sq feet.

Based on your 1100 sq. 1 square foot of net free vent area nfva per 150 feet of attic floor. 1 square foot of nfva per 300 square feet of attic floor if a vapor barrier is installed on the ceiling below. The ratio of soffit intake to roof outlet should be at least 2 1 to avoid unnecessary these heat losses from the building.

And this guideline you ll need a minimum of. 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.