Utah Climate Zones by County
Utah's 29 counties span climate zones 3B to 6B under the 2021 International Energy Conservation Code (IECC). Zone 5B is the most common, with 21 of the 29. For reference, St. George is in zone 3B, Salt Lake City is in 5B and Park City is in 6B.
Insulation minimums for each zone in Utah
| Zone | Counties | Attic | Wood-frame walls | Floors over unheated space | Basement walls |
|---|---|---|---|---|---|
| 3B | 1 | R-49 | R-20, or 13+5ci, or R-15ci | R-19 | R-5ci or R-13 |
| 5B | 21 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-30 | R-15ci, or R-19, or 13+5ci |
| 6B | 7 | 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 Utah uses
Utah enforces the 2021 IECC with amendments for homes (in effect since Jul 2024). 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
Three counties moved one zone warmer in the 2021 map: Box Elder County (6 → 5), Cache County (6 → 5), Carbon County (6 → 5). If your town still enforces the 2018 or 2015 code, the older zone applies to permits.
Every county in Utah
| Name | Zone (2021) | Zone (2018) | Details |
|---|---|---|---|
| Beaver County | 5B | 5B | Insulation → |
| Box Elder County | 5B | 6B changed | Insulation → |
| Cache County | 5B | 6B changed | Insulation → |
| Carbon County | 5B | 6B changed | Insulation → |
| Daggett County | 6B | 6B | Insulation → |
| Davis County | 5B | 5B | Insulation → |
| Duchesne County | 6B | 6B | Insulation → |
| Emery County | 5B | 5B | Insulation → |
| Garfield County | 5B | 5B | Insulation → |
| Grand County | 5B | 5B | Insulation → |
| Iron County | 5B | 5B | Insulation → |
| Juab County | 5B | 5B | Insulation → |
| Kane County | 5B | 5B | Insulation → |
| Millard County | 5B | 5B | Insulation → |
| Morgan County | 6B | 6B | Insulation → |
| Piute County | 5B | 5B | Insulation → |
| Rich County | 6B | 6B | Insulation → |
| Salt Lake County | 5B | 5B | Insulation → |
| San Juan County | 5B | 5B | Insulation → |
| Sanpete County | 5B | 5B | Insulation → |
| Sevier County | 5B | 5B | Insulation → |
| Summit County | 6B | 6B | Insulation → |
| Tooele County | 5B | 5B | Insulation → |
| Uintah County | 6B | 6B | Insulation → |
| Utah County | 5B | 5B | Insulation → |
| Wasatch County | 6B | 6B | Insulation → |
| Washington County | 3B | 3B | Insulation → |
| Wayne County | 5B | 5B | Insulation → |
| Weber County | 5B | 5B | 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 Utah?
Utah spans IECC climate zones 3B to 6B; zone 5B is the most common. Find your county in the table above, or search by ZIP code.
How much attic insulation do I need in Utah?
In Utah, 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 Utah use?
Utah enforces the 2021 IECC with amendments for homes (in effect since Jul 2024). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.
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