Required Ventilation In Attic

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.

Required ventilation in attic.

Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca. 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. Furthermore nrca also rec ommends the amount of ventila. Calculate or enter the square footage of the attic or area to be vented.

Of attic space 1 150 ventilation ratio measured at the attic floor level ceiling. 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. Most building codes require a ratio of 1 150 ventilation space to attic floor space. 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.

The following is an example shown in the irc commentary for a simple gable roof using the 1 300 ratio. Intake vents located at the lowest part of the roof under the eaves. 30 lineal feet required.