Calculating Attic Ventilation Needs

Calculate the square footage of the attic space.

Calculating attic ventilation needs.

Divide the square inches by 2. Divide the square footage item 1 by 300. Calculate or enter the square footage of the attic or area to be vented. 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.

Change the square feet to square inches. Building codes vary. 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.

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 3 2. No vapor barrier and for some municipalities in hot climates. Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches.

Ventilation manufacturers assign an nfa value to the non motorized vents they make. Of vent for every 300 sq. 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 area of your attic and the proper number of vents. 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. Calculate the square footage of your attic and provide proper attic ventilation with the right number of roof vents ridge vents or soffit vents.

1 square foot of ventilation for every 300 square feet of space. Result of item 2 x 144. If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation. Calculate the soffit vent area needed.

Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed. Measure the length and width of the attic floor space to be ventilated. How to calculate attic vent area needed when adding soffit vents. Calculate the total vent area needed.

Calculating attic ventilation requirements. Divide the total vent area by two to. Determine the amount of ventilation needed for your home with this formula.