Attic Venting Formula

So in our example we will divide the 1 500 square feet by 300.

Attic venting formula.

Calculate or enter the square footage of the attic or area to be vented. That number is divided by 2 so that the ventilation is equally distributed between the soffit and the ridge. Ridge vents are one of the easiest ways to meet roof venting requirements. This yields a total area of 1 104 square feet.

Standard attic vents like af 50 s ventilation fans or solar powered attic fans. Building codes typically echo the administration s guidelines. Ben erickson september 28 2010 at 8 03 am. 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.

Other options to meet your attic ventilation needs are. Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches. Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed. Jones has an attic space that measures 23 feet by 48 feet.

Ok so now we know the square footage of the attic area to be ventilated. The ridge vent is installed on the peak with nails and shingled over for aesthetic purposes. 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. Jones takes this measurement and divides it by 150 for a total of 7 36 square feet of ventilation space that is needed.

Now let s figure out how much ventilation space we need. Remember the minimum area requirement when using a continuous system is a ratio of 1 300. 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.