Vexing ventilation issues

Understanding building code requirements for attic ventilation

NRCA's Technical Services Section receives numerous inquiries from roofing contractors regarding attic ventilation. A large number of these inquiries relate to building code requirements and how to meet them.

Attic ventilation is addressed in the International Building Code® (IBC) and International Residential Code® (IRC). The International Code Council (ICC) publishes both publications, yet, curiously, the attic ventilation requirements contained in these publications are not identical. Although the latest versions of these codes were published earlier this year, many jurisdictions still use the 2009 edition; I will discuss both codes and editions and address some issues I found confusing.

Figure 1: Side-by-side comparison of attic ventilation requirements
Click on the image above to view the table in its entirety.

To ease the discussion, I compiled a summary chart showing a side-by-side comparison of the attic ventilation requirements excerpted from the codes (see Figure 1). The chart also includes section references indicating where the requirements can be found within each code. I encourage you to refer to this chart as you read the article.

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