Calculating Attic Ventilation Needs

Calculate or enter the square footage of the attic or area to be vented.

Calculating attic ventilation needs.

Divide the square inches by 2. Result of item 3 2. Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed. 1 cubic foot is 12 x 12 144 cubic inches.

Divide the total vent area by two to. Calculate the area of your attic and the proper number of vents. Change the square feet to square inches. 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 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. No vapor barrier and for some municipalities in hot climates. Divide the square footage item 1 by 300. Result of item 1 300.

Building codes vary. Calculating attic ventilation requirements. Calculate the total vent area needed. In order to find the right calculator divide the attic floor space by 300 sq feet.

1 square foot of ventilation for every 150 square feet of space. The home ventilating institute hvi recommends that powered attic ventilators provide at least 10 air changes per hour to equalize attic temperature. If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation. Measure the length and width of the attic floor space to be ventilated.

Enter your square footage. Result of item 2 x 144. Calculate the square footage of the attic space. Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches.

How to calculate attic vent area needed when adding soffit vents. Next multiply the 4 square feet into cubic inches. Calculate the soffit vent area needed. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq.

For pitched roofs with vapor barriers. Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find. Of vent for every 300 sq.