Hawaii Climate Zones by County
All five of Hawaii's counties are in climate zone 1A under the 2021 International Energy Conservation Code (IECC).
Insulation minimums in Hawaii (zone 1A)
| Zone | Attic | Wood-frame walls | Floors over unheated space | Basement walls |
|---|---|---|---|---|
| 1A | R-30 | R-13, or R-10ci | R-13 | None required |
Minimums from the 2021 IECC (Table R402.1.3). Many areas still enforce an older edition, so check with your local building department. See sources.
Which energy code Hawaii uses
Hawaii enforces the 2018 IECC with amendments for homes (in effect since Dec 2020), though local governments have a say in how it is adopted and enforced. Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments. See every state's energy code.
What changed from the 2018 map
None of Hawaii's counties changed zone between the 2018 and 2021 maps.
Every county in Hawaii
| Name | Zone (2021) | Zone (2018) | Details |
|---|---|---|---|
| Hawaii County | 1A | 1A | Insulation → |
| Honolulu County | 1A | 1A | Insulation → |
| Kalawao County | 1A | 1A | Insulation → |
| Kauai County | 1A | 1A | Insulation → |
| Maui County | 1A | 1A | Insulation → |
Source: Pacific Northwest National Laboratory, Guide to Determining Climate Zone by County: Building America and IECC 2021 Updates (2022).
Frequently asked questions
What climate zone is Hawaii?
Hawaii is IECC climate zone 1A under the 2021 code.
How much attic insulation do I need in Hawaii?
The 2021 IECC calls for R-30 in the attic everywhere in Hawaii.
What energy code does Hawaii use?
Hawaii enforces the 2018 IECC with amendments for homes (in effect since Dec 2020), though local governments have a say in how it is adopted and enforced. Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.
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