Calculating Attic Ventilation Needs

Calculate the soffit vent area needed.

Calculating attic ventilation needs.

Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find. 1 cubic foot is 12 x 12 144 cubic inches. If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq.

Calculate the square footage of the attic space. 1 square foot of ventilation for every 300 square feet of space. Ventilation manufacturers assign an nfa value to the non motorized vents they make. Of vent for every 300 sq.

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

Calculating attic ventilation requirements. Determine the amount of ventilation needed for your home with this formula. Calculate or enter the square footage of the attic or area to be vented. Divide the total vent area by two to.

Measure the length and width of the attic floor space to be ventilated. Result of item 2 x 144. For pitched roofs with vapor barriers. In order to find the right calculator divide the attic floor space by 300 sq feet.

Result of item 1 300. No vapor barrier and for some municipalities in hot climates. The home ventilating institute hvi recommends that powered attic ventilators provide at least 10 air changes per hour to equalize attic temperature. 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.

Divide the square footage item 1 by 300. Calculate the area of your attic and the proper number of vents. Enter your square footage. Divide the square inches by 2.

Result of item 3 2. 1 square foot of ventilation for every 150 square feet of space. Next multiply the 4 square feet into cubic inches.