Attic Venting Formula

The ridge vent is installed on the peak with nails and shingled over for aesthetic purposes.

Attic venting formula.

Other options to meet your attic ventilation needs are. Building codes typically echo the administration s guidelines. Remember the minimum area requirement when using a continuous system is a ratio of 1 300. Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed.

Now let s figure out how much ventilation space we need. So in our example we will divide the 1 500 square feet by 300. Jones takes this measurement and divides it by 150 for a total of 7 36 square feet of ventilation space that is needed. 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.

That number is divided by 2 so that the ventilation is equally distributed between the soffit and the ridge. Calculate or enter the square footage of the attic or area to be vented. 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.

Standard attic vents like af 50 s ventilation fans or solar powered attic fans. This yields a total area of 1 104 square feet. Ridge vents are one of the easiest ways to meet roof venting requirements. Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches.

Ok so now we know the square footage of the attic area to be ventilated. Ben erickson september 28 2010 at 8 03 am. Ventilation manufacturers assign an nfa value to the non motorized vents they make.