Attic Ventilation Requirements Irc

The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures.

Attic ventilation requirements irc.

Ventilation openings shall have a least dimension of 1 16 inch 1 6 mm minimum and 1 4 inch 6 4 mm maximum. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Vented attics shall have a minimum net free ventilation area at least 1 300 of the area of the vented space. For large volume attics such as where roof slopes.

Nrca guidelines 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. The minimum amount of attic ventilation remains 1 150 1 square foot of net free area for every 150 square feet of 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. 2015 international residential code for attic ventilation air vent inc.

Between half and two thirds of the provided ventilation shall be installed at the eaves. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Attic floor is defined as length x width floor of the attic. Always have a balanced ventilation system.

The following are the requirements taken directly from the irc. Air vent provides a complete line of ventilation products that meet the highest standards for quality and performance. Also when using a vapor retarder in an attic space irc 2012 limits the net free ventilation reduction from 1 150 to 1 300 for buildings in climate zones 6 7 and 8. 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.

In no case should the amount of exhaust ventilation exceed the amount of intake ventilation. The international code council icc is a non profit organization dedicated to developing model codes and standards used in the design build and compliance process.