Cavity Only Insulation-A Correction to the 2021 IRC Energy Code

This post first appeared on the Green Building Advisor Website

I recently wrote a two-part article covering the benefits, challenges and code requirements for continuous insulation.  (You can read the articles here and here.)  In the first article, I referenced table R402.1.3 which is found in Chapter 11, Energy Efficiency.  The table shows the R-value and U-factor requirements for several building components and assemblies.  The table data was taken from the first edition printing of the 2021 IRC.  In the article, I stated, “Climate zones 1, 2, and 3 are unique in that they have the option of cavity-only insulation.  Climate zones 4 through 8 all are required to have some amount of continuous insulation.”  A reader on the Green Building Advisor Website, jimmybpsu, pointed out in the comments section of the article that he had a different version of table R402.1.3 which did allow for cavity only insulation in climate zones 4-8.  As it turned out, he was right.

My son Colter installing a R-30 Rockwool Batt.

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