Calculating Attic Ventilation Needs

How to calculate attic vent area needed when adding soffit vents.

Calculating attic ventilation needs.

Next multiply the 4 square feet into cubic inches. Of vent for every 300 sq. Result of item 3 2. Measure the length and width of the attic floor space to be ventilated.

Enter your square footage. 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. Change the square feet to square inches.

Result of item 1 300. Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find. Calculate the area of your attic and the proper number of vents. Divide the total vent area by two to.

Calculate or enter the square footage of the attic or area to be vented. No vapor barrier and for some municipalities in hot climates. 1 square foot of ventilation for every 300 square feet of space. Building codes vary.

In order to find the right calculator divide the attic floor space by 300 sq feet. Result of item 2 x 144. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. 1 square foot of ventilation for every 150 square feet of space.

Calculate the square footage of your attic and provide proper attic ventilation with the right number of roof vents ridge vents or soffit vents. If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation. Divide the square inches by 2. Ventilation manufacturers assign an nfa value to the non motorized vents they make.

Calculate the soffit vent area needed. 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. Calculate the total vent area needed. 1 cubic foot is 12 x 12 144 cubic inches.

Calculate the square footage of the attic space. The home ventilating institute hvi recommends that powered attic ventilators provide at least 10 air changes per hour to equalize attic temperature. For pitched roofs with vapor barriers.