Roof Venting Formula

Now you know how many square inches of attic roof venting you need for the roof and soffit.

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. A ridge vent is installed at the peak of the roof where the hot air rises to. Our roof is 50 feet long so using a standard product we will get 900 square inches of ventilating space. Next divide that number by 2.

And this guideline you ll need a minimum of. Here s a rule of thumb to follow. The federal housing administration recommends 1 square foot of attic ventilation for every 150 square feet of attic space. Up to 6 12 roof pitch use the standard formula as explained in this article.

The idea of roof vents existed for hundreds of years with natural vents employed in chinese buildings during the tang dynasty natural ventilation ducts in the buddhist monks caves and wind catchers incorporated in arabian architecture. 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. 7 12 to 10 12 roof pitches increase the amount of ventilation by 20 percent. Generally as the roof pitch increases the volume inside the attic also increases along with the amount of needed attic ventilation.

How to specify the proper roof intake and outlet vent area ratios to stop building heat loss and provide proper attic venting to avoid condensation ice dam leaks mold roof structure damage table of types of ridge vents and net free venting area per linear foot list of roof outlet ventilation products comparing equivalent ventilation area provided by each questions answers about attic moisture condensation ventilation. One of the easiest and most effective ways of ventilation on a roof is to use a ridge vent. Near ridge of the roof. So the ridge ventilation has exceeded the minimum requirement.

Vent roofs with steeples towers or cupolas can be found in different buildings from barns to cathedrals. What is the proper ratio of soffit intake to ridge outlet. Vents are rated by their net free area or the amount of space for air to flow in or out. 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.

Nine hundred square inches equals 6 25 square feet. 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. Based on your 1100 sq. Standard ridge vent produces 18 square inches of ventilating area per lineal foot.