Roof Venting Formula

One of the easiest and most effective ways of ventilation on a roof is to use a ridge vent.

Roof venting formula.

Now you know how many square inches of attic roof venting you need for the roof and soffit. Choose one of the following products to meet the recommended exhaust nfva of 528 square inches. Next divide that number by 2. Soffit vents allow outside air to.

A ridge vent is installed at the peak of the roof where the hot air rises to. Ventsure 4 foot strip heat moisture ridge vent. A 50 x 30 attic would have a total area of 1 500 sq. Calculate the total vent area needed.

7 12 to 10 12 roof pitches increase the amount of ventilation by 20 percent. How to determine the number of attic vents. 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. Ft divided by 150 equals 10 sq.

Length x width of attic in feet 150 total sq. Two square feet equals 288 square inches. Ventsure 4 foot strip heat moisture ridge vent with weather protector moisture barrier. For projects involving vents with motors the calculation formula is different.

So we would need at least six metal vents in addition to the lower soffit ventilation to meet minimum 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. 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. 27 lineal feet required.

The calculations before indicated that we needed 2 square feet of ridge or upper roof ventilation. Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find the total square feet of vent space needed. 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. 11 12 roof pitch and higher increase the amount of ventilation by 30 percent.

Up to 6 12 roof pitch use the standard formula as explained in this article.