Calculating Minimum Attic Ventilation

Calculate the square footage of the attic space.

Calculating minimum attic ventilation.

Divide the square footage item 1 by 300. Length x width of attic in feet 150 total sq. Result of item 2 x 144. 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.

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. For balanced ventilation an equal amount of intake vent area net free area should also be installed. The following is an example shown in the irc commentary for a simple gable roof using the 1 300 ratio. Of total vent space needed.

The result of item 4 is the minimum of square inch. 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. A discussion on attic ventilation isn t complete without going over the calculations to determine the minimum required net free ventilating area nfva. 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.

Current regulations state that the minimum attic ventilation requirements are 150 1. Calculate the total vent area needed. Result of item 3 2. Enter square footage calculate or enter the square footage of the attic or area to be vented.

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. 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. 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.

Let s use the following simple ranch house for an example. Calculating attic ventilation requirements. This means that if you have a 1500 sq attic then you would need at least 10 sf of ventilation. Result of item 1 300.

The house measures 30 feet by 50 feet. 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. Ft divided by 150 equals 10 sq.

Attic ventilation is an important part of keeping your building healthy. Calculating ventilation area of attic kitchen ventilation text. Use avp s roof vent calculator to determine the number and size of exhaust vents you will need.