Calculating Attic Ventilation Needs

Measure the length and width of the attic floor space to be ventilated.

Calculating attic ventilation needs. In order to find the right calculator divide the attic floor space by 300 sq feet. For pitched roofs with vapor barriers. Determine the amount of ventilation needed for your home with this formula. Calculate the area of your attic and the proper number of vents.

Calculate or enter the square footage of the attic or area to be vented. Result of item 2 x 144. Divide the square inches by 2. Calculating attic ventilation requirements.

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. 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. 1 cubic foot is 12 x 12 144 cubic inches.

Calculate the soffit vent area needed. Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find. Calculate the total vent area needed. Building codes vary.

Divide the square footage item 1 by 300. The home ventilating institute hvi recommends that powered attic ventilators provide at least 10 air changes per hour to equalize attic temperature. Next multiply the 4 square feet into cubic inches. 1 square foot of ventilation for every 300 square feet of space.

Of vent for every 300 sq. Calculate the square footage of your attic and provide proper attic ventilation with the right number of roof vents ridge vents or soffit vents. Result of item 1 300. Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches.

Enter your square footage. Calculate the square footage of the attic space. No vapor barrier and for some municipalities in hot climates. Change the square feet to square inches.

Result of item 3 2. How to calculate attic vent area needed when adding soffit vents. If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation.