Calculating Attic Ventilation Needs

Result of item 1 300.

Calculating attic ventilation needs.

Divide the square inches by 2. Calculate the soffit vent area needed. Divide the total vent area by two to. Calculating attic ventilation requirements.

Of vent for every 300 sq. Calculate or enter the square footage of the attic or area to be vented. In order to find the right calculator divide the attic floor space by 300 sq feet. 1 square foot of ventilation for every 300 square feet of space.

In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. 1 cubic foot is 12 x 12 144 cubic inches. Next multiply the 4 square feet into cubic inches. For pitched roofs with vapor barriers.

Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches. Result of item 2 x 144. Calculate the square footage of your attic and provide proper attic ventilation with the right number of roof vents ridge vents or soffit vents. Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed.

Result of item 3 2. The home ventilating institute hvi recommends that powered attic ventilators provide at least 10 air changes per hour to equalize attic temperature. No vapor barrier and for some municipalities in hot climates. How to calculate attic vent area needed when adding soffit vents.

Measure the length and width of the attic floor space to be ventilated. 1 square foot of ventilation for every 150 square feet of space. Ventilation manufacturers assign an nfa value to the non motorized vents they make. Attic ventilation calculator effective attic ventilation requires air to exit at or near the peak of the roof and replacement air to be drawn in under the eaves of the house via soffit venting.

Enter your square footage. Calculate the square footage of the attic space. Calculate the area of your attic and the proper number of vents. Change the square feet to square inches.

If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation. Calculate the total vent area needed. Divide the square footage item 1 by 300.