Roof Venting Formula

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 venting formula.

So we would need at least six metal vents in addition to the lower soffit ventilation to meet minimum ventilation requirements. How to determine the number of attic vents. Ft divided by 150 equals 10 sq. Ventsure 4 foot strip heat moisture ridge vent.

The calculations before indicated that we needed 2 square feet of ridge or upper roof ventilation. A ridge vent is installed at the peak of the roof where the hot air rises to. Soffit vents allow outside air to. Now you know how many square inches of attic roof venting you need for the roof and soffit.

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. 27 lineal feet required. A normal metal pot vent produces only 50 squares inches of free net area. Up to 6 12 roof pitch use the standard formula as explained in this article.

Ventsure 4 foot strip heat moisture ridge vent with weather protector moisture barrier. Calculate the total vent area needed. Choose one of the following products to meet the recommended exhaust nfva of 528 square inches. Proper air circulation through the attic space helps lower cooling bills and prolongs the life of roofing materials.

One of the easiest and most effective ways of ventilation on a roof is to use a ridge vent. For projects involving vents with motors the calculation formula is different. 7 12 to 10 12 roof pitches increase the amount of ventilation by 20 percent. 11 12 roof pitch and higher increase the amount of ventilation by 30 percent.

Of total vent space needed. A 50 x 30 attic would have a total area of 1 500 sq. Length x width of attic in feet 150 total sq. Two square feet equals 288 square inches.

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.