IECC minimum attic and wall R-values across all eight climate zones
The colder your zone, the more insulation the code requires — attic minimums climb from R-30 to R-60 and walls from R-13 to R-30, then plateau in the coldest zones.
What this diagram shows
A bar chart of the 2021 IECC prescriptive minimum insulation R-values for the attic and the exterior wall across all eight climate zones. The attic minimum rises from R-30 in zone 1 to R-49 in zones 2 and 3 and R-60 in zones 4 through 8. The wall minimum rises from R-13 in zones 1 and 2 to R-20 in zone 3 and R-30 in zones 4 through 8. Requirements climb steeply through the warm and mixed zones, then plateau in the cold northern zones. This is why looking up your climate zone is the first step in any insulation or envelope job.
Climate Zone Calculator
Find your IECC climate zone by ZIP code or county, plus the code-required insulation R-values and window U-factors for your zone. Free, no signup.
Related diagrams
Insulation & ClimateWhat R-value means — the same R-30 takes very different thickness by material
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