Arizona Climate Zones by County
Arizona's 15 counties span climate zones 2B to 5B under the 2021 International Energy Conservation Code (IECC). Zone 3B is the most common, with 5 of the 15. For reference, Phoenix and Tucson are in zone 2B and Flagstaff is in 5B.
Insulation minimums for each zone in Arizona
| Zone | Counties | Attic | Wood-frame walls | Floors over unheated space | Basement walls |
|---|---|---|---|---|---|
| 2B | 5 | R-49 | R-13, or R-10ci | R-13 | None required |
| 3B | 5 | R-49 | R-20, or 13+5ci, or R-15ci | R-19 | R-5ci or R-13 |
| 4B | 2 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-19 | R-10ci or R-13 |
| 5B | 3 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-30 | R-15ci, or R-19, or 13+5ci |
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 Arizona uses
Arizona has no statewide residential energy code; cities and counties adopt their own, so check with your local building department. 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 Arizona's counties changed zone between the 2018 and 2021 maps.
Every county in Arizona
| Name | Zone (2021) | Zone (2018) | Details |
|---|---|---|---|
| Apache County | 5B | 5B | Insulation → |
| Cochise County | 3B | 3B | Insulation → |
| Coconino County | 5B | 5B | Insulation → |
| Gila County | 4B | 4B | Insulation → |
| Graham County | 3B | 3B | Insulation → |
| Greenlee County | 3B | 3B | Insulation → |
| La Paz County | 2B | 2B | Insulation → |
| Maricopa County | 2B | 2B | Insulation → |
| Mohave County | 3B | 3B | Insulation → |
| Navajo County | 5B | 5B | Insulation → |
| Pima County | 2B | 2B | Insulation → |
| Pinal County | 2B | 2B | Insulation → |
| Santa Cruz County | 3B | 3B | Insulation → |
| Yavapai County | 4B | 4B | Insulation → |
| Yuma County | 2B | 2B | 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 Arizona?
Arizona spans IECC climate zones 2B to 5B; zone 3B is the most common. Find your county in the table above, or search by ZIP code.
How much attic insulation do I need in Arizona?
In Arizona, the 2021 IECC calls for R-49 and R-60 in the attic, depending on the zone. The table near the top of this page lists each zone's minimums.
What energy code does Arizona use?
Arizona has no statewide residential energy code; cities and counties adopt their own, so check with your local building department. Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.
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