Calculating Attic Ventilation Needs

Result of item 2 x 144.

Calculating attic ventilation needs.

Calculate the square footage of your attic and provide proper attic ventilation with the right number of roof vents ridge vents or soffit vents. How to calculate attic vent area needed when adding soffit vents. For pitched roofs with vapor barriers. Calculate the soffit vent area needed.

1 square foot of ventilation for every 150 square feet of space. If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation. 1 square foot of ventilation for every 300 square feet of space. In order to find the right calculator divide the attic floor space by 300 sq feet.

Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. Next multiply the 4 square feet into cubic inches. Calculate the square footage of the attic space.

Result of item 3 2. Of vent for every 300 sq. Calculate the area of your attic and the proper number of vents. 1 cubic foot is 12 x 12 144 cubic inches.

Determine the amount of ventilation needed for your home with this formula. Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches. The home ventilating institute hvi recommends that powered attic ventilators provide at least 10 air changes per hour to equalize attic temperature. Result of item 1 300.

Change the square feet to square inches. Building codes vary. Divide the total vent area by two to. Calculate the total vent area needed.

Enter your square footage. Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find. Ventilation manufacturers assign an nfa value to the non motorized vents they make. Calculating attic ventilation requirements.

Divide the square inches by 2. No vapor barrier and for some municipalities in hot climates. 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.