Irc Attic Ventilation Requirements

More ventilation at the soffitsthan at the ridge will allow the attic to be slightly pressurized irc 2012 requirements reflect this approach for best results provide 50 to 75 of ventilation space at the soffits 60 40 is the optimal split.

Irc attic ventilation requirements.

Vented attics shall have a minimum net free ventilation area at least 1 300 of the area of the vented space. 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. For large volume attics such as where roof slopes. The following are the requirements taken directly from the irc.

Pdf 2015 international residential code for attic ventilation 145 kb. 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. 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. The ventilation openings shall have a least dimension of 1 16 inch 1 6 mm minimum and 1 4 inch 6 4 mm maximum.

Between half and two thirds of the provided ventilation shall be installed at the eaves. The ventilation amount and opening size requirements can be found in section 806 roof ventilation of chapter 8 roof ceiling construction. Attic floor is defined as length x width floor of the attic. The amount of ventilation can be reduced to 1 300 in effect 50 less but 2 conditions must be met effective 1 1 18.

The majority of the requirements related to attic ventilation have not changed much from the previous editions. The minimum net area of ventilation openings shall be not less than 1 square foot for each 150 square feet of under floor space area unless the ground surface is covered by class 1 vapor retarder material.