Calculating Minimum Attic Ventilation

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.

Calculating minimum attic ventilation.

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. Divide the square footage item 1 by 300. Calculating ventilation area of attic kitchen ventilation text. The result of item 4 is the minimum of square inch.

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. This means that if you have a 1500 sq attic then you would need at least 10 sf of ventilation. 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.

Length x width of attic in feet 150 total sq. In order to have a balanced ventilation system you need to have the right roof vent calculation. Calculate the total vent area needed. A discussion on attic ventilation isn t complete without going over the calculations to determine the minimum required net free ventilating area nfva.

The following is an example shown in the irc commentary for a simple gable roof using the 1 300 ratio. Divide the square inches by 2. Attic ventilation is an important part of keeping your building healthy. Calculate the square footage of the attic space.

A 50 x 30 attic would have a total area of 1 500 sq. Result of item 1 300. Result of item 3 2. Change the square feet to square inches.

For balanced ventilation an equal amount of intake vent area net free area should also be installed. Let s use the following simple ranch house for an example. The house measures 30 feet by 50 feet. The federal housing authority fha and the urban development hud have established minimum requirements for attic ventilation.

Current regulations state that the minimum attic ventilation requirements are 150 1. Result of item 2 x 144. Use avp s roof vent calculator to determine the number and size of exhaust vents you will need. 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.

Calculating attic ventilation requirements. 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. Enter square footage calculate or enter the square footage of the attic or area to be vented.