Attic Venting Formula

Ben erickson september 28 2010 at 8 03 am.

Attic 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. Ridge vents are one of the easiest ways to meet roof venting requirements. The federal housing administration recommends 1 square foot of attic ventilation for every 150 square feet of attic space. That number is divided by 2 so that the ventilation is equally distributed between the soffit and the ridge.

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. 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. Standard attic vents like af 50 s ventilation fans or solar powered attic fans. Building codes typically echo the administration s guidelines.

Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches. Ventilation manufacturers assign an nfa value to the non motorized vents they make. Now let s figure out how much ventilation space we need. Other options to meet your attic ventilation needs are.

Calculate or enter the square footage of the attic or area to be vented. Jones takes this measurement and divides it by 150 for a total of 7 36 square feet of ventilation space that is needed. 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.

Remember the minimum area requirement when using a continuous system is a ratio of 1 300. Jones has an attic space that measures 23 feet by 48 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.