Calculating Minimum Attic Ventilation

Current regulations state that the minimum attic ventilation requirements are 150 1.

Calculating minimum attic ventilation.

Calculating attic ventilation requirements. For balanced ventilation an equal amount of intake vent area net free area should also be installed. The house measures 30 feet by 50 feet. 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.

The federal housing authority fha and the urban development hud have established minimum requirements for attic ventilation. 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. Result of item 3 2. 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. Let s use the following simple ranch house for an example. A 50 x 30 attic would have a total area of 1 500 sq. Change the square feet to square inches.

Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find the total square feet of vent space needed. Attic ventilation is an important part of keeping your building healthy. The following is an example shown in the irc commentary for a simple gable roof using the 1 300 ratio. Calculating ventilation area of attic kitchen ventilation text.

Divide the square inches by 2. 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 footage item 1 by 300. 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.

In order to have a balanced ventilation system you need to have the right roof vent calculation. Result of item 2 x 144. Enter square footage calculate or enter the square footage of the attic or area to be vented. Result of item 1 300.

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. This means that if you have a 1500 sq attic then you would need at least 10 sf of ventilation. Calculate the square footage of the attic space. Ft divided by 150 equals 10 sq.

According to their requirements you should have 1 square foot of attic ventilation per 300 sq ft of attic floor space. 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. Of total vent space needed.