Attic Venting Formula

Calculate or enter the square footage of the attic or area to be vented.

Attic venting formula.

The ridge vent is installed on the peak with nails and shingled over for aesthetic purposes. This yields a total area of 1 104 square feet. That number is divided by 2 so that the ventilation is equally distributed between the soffit and the ridge. Jones has an attic space that measures 23 feet by 48 feet.

Other options to meet your attic ventilation needs are. Building codes typically echo the administration s guidelines. 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. The federal housing administration recommends 1 square foot of attic ventilation for every 150 square feet of attic space.

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. Ventilation manufacturers assign an nfa value to the non motorized vents they make. Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed. Ben erickson september 28 2010 at 8 03 am.

So in our example we will divide the 1 500 square feet by 300. Ok so now we know the square footage of the attic area to be ventilated. Jones takes this measurement and divides it by 150 for a total of 7 36 square feet of ventilation space that is needed. Standard attic vents like af 50 s ventilation fans or solar powered attic fans.

Remember the minimum area requirement when using a continuous system is a ratio of 1 300. Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches. 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.