Required Ventilation In Attic

Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents.

Required ventilation in attic. Intake vents located at the lowest part of the roof under the eaves. The following is an example shown in the irc commentary for a simple gable roof using the 1 300 ratio. Of attic space 1 150 ventilation ratio measured at the attic floor level ceiling. Calculate or enter the square footage of the attic or area to be vented.

For large volume attics such as where roof slopes are greater than 8 12 designers also should consider increasing the amount of attic ventilation to account for the additional volume of attic 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. 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. A discussion on attic ventilation isn t complete without going over the calculations to determine the minimum required net free ventilating area nfva.

Most building codes require a ratio of 1 150 ventilation space to attic floor space. You can also contact your local municipality to check on building code in your area. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.