Calculating Minimum Attic Ventilation

Calculate the total vent area needed.

Calculating minimum attic ventilation.

Calculating attic ventilation requirements. Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge. Attic ventilation is an important part of keeping your building healthy. Ok to determine how much ventilation area you need for your house all you need to know is the square foot area of the attic to be ventilated.

For balanced ventilation an equal amount of intake vent area net free area should also be installed. The federal housing authority fha and the urban development hud have established minimum requirements for attic ventilation. According to their requirements you should have 1 square foot of attic ventilation per 300 sq ft of attic floor space. Change the square feet to square inches.

Of total vent space needed. Let owens corning roofing help you calculate exactly how much ventilation you will need for a healthy and balanced attic with our 4 step ventilation calculator. Ft divided by 150 equals 10 sq. A discussion on attic ventilation isn t complete without going over the calculations to determine the minimum required net free ventilating area nfva.

Divide the square inches by 2. Calculate the square footage of the attic space. Result of item 3 2. Divide the square footage item 1 by 300.

Length x width of attic in feet 150 total sq. Result of item 1 300. This means that if you have a 1500 sq attic then you would need at least 10 sf of ventilation. The house measures 30 feet by 50 feet.

Current regulations state that the minimum attic ventilation requirements are 150 1. Calculating ventilation area of attic kitchen ventilation text. Enter square footage calculate or enter the square footage of the attic or area to be vented. Result of item 2 x 144.

Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space. Use avp s roof vent calculator to determine the number and size of exhaust vents you will need. The following is an example shown in the irc commentary for a simple gable roof using the 1 300 ratio. A 50 x 30 attic would have a total area of 1 500 sq.

In order to have a balanced ventilation system you need to have the right roof vent calculation. Let s use the following simple ranch house for an example. The result of item 4 is the minimum of square inch.