Attic Venting Formula

Building codes typically echo the administration s guidelines.

Attic venting formula.

Ventilation manufacturers assign an nfa value to the non motorized vents they make. Now let s figure out how much ventilation space we need. This yields a total area of 1 104 square feet. The ridge vent is installed on the peak with nails and shingled over for aesthetic purposes.

Remember the minimum area requirement when using a continuous system is a ratio of 1 300. 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. Ok so now we know the square footage of the attic area to be ventilated. Every formula for attic ventilation i ve seen says 1 sq ft of ventilation is required for every 300 sq ft of attic floor space.

Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches. The federal housing administration recommends 1 square foot of attic ventilation for every 150 square feet of attic space. 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. Jones has an attic space that measures 23 feet by 48 feet.

Ben erickson september 28 2010 at 8 03 am. Ridge vents are one of the easiest ways to meet roof venting requirements. Standard attic vents like af 50 s ventilation fans or solar powered attic fans. Calculate or enter the square footage of the attic or area to be vented.

Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed. So in our example we will divide the 1 500 square feet by 300. Let owens corning roofing help you calculate exactly how much ventilation you will need for a healthy and balanced attic with our 4 step ventilation calculator.