Irc Attic Ventilation Requirements

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.

Irc attic ventilation requirements.

The majority of the requirements related to attic ventilation have not changed much from the previous editions. The amount of ventilation can be reduced to 1 300 in effect 50 less but 2 conditions must be met effective 1 1 18. Attic floor is defined as length x width floor of the attic. 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.

2015 international residential code for attic ventilation the code minimum ratio is 1 150. The following are the requirements taken directly from the irc. 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. The ventilation openings shall have a least dimension of 1 16 inch 1 6 mm minimum and 1 4 inch 6 4 mm maximum.

The ventilation amount and opening size requirements can be found in section 806 roof ventilation of chapter 8 roof ceiling construction. 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. Vented attics shall have a minimum net free ventilation area at least 1 300 of the area of the vented space. 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.

Between half and two thirds of the provided ventilation shall be installed at the eaves. Pdf 2015 international residential code for attic ventilation 145 kb.