Calculating Minimum Attic Ventilation

Attic ventilation is an important part of keeping your building healthy.

Calculating minimum attic ventilation.

Current regulations state that the minimum attic ventilation requirements are 150 1. 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. A discussion on attic ventilation isn t complete without going over the calculations to determine the minimum required net free ventilating area nfva.

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

Calculate the total vent area needed. A 50 x 30 attic would have a total area of 1 500 sq. This means that if you have a 1500 sq attic then you would need at least 10 sf of ventilation. The federal housing authority fha and the urban development hud have established minimum requirements for attic ventilation.

Divide the square footage item 1 by 300. Result of item 2 x 144. Of total vent space needed. The following is an example shown in the irc commentary for a simple gable roof using the 1 300 ratio.

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. Result of item 1 300. Divide the square inches by 2. The house measures 30 feet by 50 feet.

Calculating attic ventilation requirements. Use avp s roof vent calculator to determine the number and size of exhaust vents you will need. Change the square feet to square inches. Result of item 3 2.

Ft divided by 150 equals 10 sq. Calculating ventilation area of attic kitchen ventilation text. For balanced ventilation an equal amount of intake vent area net free area should also be installed. 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. 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. Enter square footage calculate or enter the square footage of the attic or area to be vented.