1 150 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.

1 150 attic ventilation.

Most building codes require a ratio of 1 150 ventilation space to 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. Calculating ventilation area of attic kitchen ventilation text. 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.

According to the national roofing contractors association nrca a power vent with an airflow rate of 1 0 cubic foot per minute per square foot of attic space measured at the attic floor is generally considered to be equivalent to a 1 150 ventilation ratio. Owens corning recommends a balanced ventilation system based on the u s. 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. Let s use the following simple ranch house for an example.

The house measures 30 feet by 50 feet. 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. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. 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. You can also contact your local municipality to check on building code in your area. Ft of attic space 1 square foot of ventilation is recommended. 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.

Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca. 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.