1 150 Attic Ventilation

The recommended ventilation ratio to provide for vented attic assemblies when an air barrier is present is the 1 300 ratio as specified by most building codes.

1 150 attic ventilation. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. According to the 2018 irc code on attic ventilation the minimum net free ventilating area nfva shall be 1 150 of the area of the vented space. 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. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.

You can also contact your local municipality to check on building code in your area. 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. For every 150 square feet sq. Intake vents located at the lowest part of the roof under the eaves allow cool.

This is based principally on good historical experience and simple psychrometric analysis handegord giroux 1984. The house measures 30 feet by 50 feet. 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. Regarding attic ventilation nrca recommends designers provide at least 1 square foot of nfva for every 150 square feet of attic space 1 150 ventilation ratio measured at the attic floor level ceiling.

Owens corning recommends a balanced ventilation system based on the u s. Most building codes require a ratio of 1 150 ventilation space to attic floor space. Let s use the following simple ranch house for an example. Calculating ventilation area of attic kitchen ventilation text.

When you purchase vents check the square inches for those vents they range from 38 49 or as high as 100 inches per vent so do the math. 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.