Calculating Attic Ventilation Needs

No vapor barrier and for some municipalities in hot climates.

Calculating attic ventilation needs.

1 square foot of ventilation for every 300 square feet of space. Change the square feet to square inches. Ventilation manufacturers assign an nfa value to the non motorized vents they make. Calculate the area of your attic and the proper number of vents.

Calculate the square footage of your attic and provide proper attic ventilation with the right number of roof vents ridge vents or soffit vents. Calculate the soffit vent area needed. Building codes vary. Calculate the total vent area needed.

For pitched roofs with vapor barriers. Result of item 2 x 144. Determine the amount of ventilation needed for your home with this formula. Of vent for every 300 sq.

Divide the square footage item 1 by 300. Calculating attic ventilation requirements. The home ventilating institute hvi recommends that powered attic ventilators provide at least 10 air changes per hour to equalize attic temperature. Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find.

Next multiply the 4 square feet into cubic inches. Calculate the square footage of the attic space. Measure the length and width of the attic floor space to be ventilated. Calculate or enter the square footage of the attic or area to be vented.

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. In order to find the right calculator divide the attic floor space by 300 sq feet. Divide the square inches by 2.

Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches. Result of item 1 300. Divide the total vent area by two to. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq.

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. 1 square foot of ventilation for every 150 square feet of space.