Calculating Attic Ventilation Needs

Enter your square footage.

Calculating attic ventilation needs.

Of vent for every 300 sq. 1 square foot of ventilation for every 300 square feet of space. Change the square feet to square inches. 1 cubic foot is 12 x 12 144 cubic inches.

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. Next multiply the 4 square feet into cubic inches. Result of item 2 x 144. For pitched roofs with vapor barriers.

In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. No vapor barrier and for some municipalities in hot climates. How to calculate attic vent area needed when adding soffit vents. Calculating attic ventilation requirements.

Calculate or enter the square footage of the attic or area to be vented. Calculate the square footage of the attic space. If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation. Divide the square inches by 2.

Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches. Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find. Building codes vary. Ventilation manufacturers assign an nfa value to the non motorized vents they make.

Calculate the total vent area needed. Result of item 1 300. Divide the total vent area by two to. The home ventilating institute hvi recommends that powered attic ventilators provide at least 10 air changes per hour to equalize attic temperature.

Determine the amount of ventilation needed for your home with this formula. 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 150 square feet of space. Calculate the soffit vent area needed.

Divide the square footage item 1 by 300. 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.