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Zone 2 wall insulation code

Bbrown3381 | Posted in GBA Pro Help on

Was reviewing the IRC for insulation requirements for zone 2. Wood frame walls at 13 and mass walls with exterior foam at 4. Why the difference? And this brings up the real question which is: I’m about to put rigid foam on the exterior of a single story block house……any idea what the r value I should shoot for before reaching the point of diminishing returns?

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  1. iLikeDirt | | #1

    The difference is because insulated thermal mass walls like yours will outperform light wood framed walls that have more insulation but less mass. More insulation is always better, of course, but in your climate R-10 is probably all you'll ever really need considering that it'll be outboard of block walls. But if you're adding anything at all, the marginal cost of going from R-4 or 5 to R-8 to 10 is so small that it'll probably be worth it.

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