Idaho Climate Zones by County
Idaho's 44 counties span climate zones 5B to 6B under the 2021 International Energy Conservation Code (IECC). Zone 5B is the most common, with 22 of the 44. For reference, Coeur d'Alene is in zone 5B and Pocatello and Idaho Falls are in 6B.
Insulation minimums for each zone in Idaho
| Zone | Counties | Attic | Wood-frame walls | Floors over unheated space | Basement walls |
|---|---|---|---|---|---|
| 5B | 22 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-30 | R-15ci, or R-19, or 13+5ci |
| 6B | 22 | 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 Idaho uses
Idaho enforces the 2018 IECC with amendments for homes (in effect since Jan 2021). 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 Idaho's counties changed zone between the 2018 and 2021 maps.
Every county in Idaho
| Name | Zone (2021) | Zone (2018) | Details |
|---|---|---|---|
| Ada County | 5B | 5B | Insulation → |
| Adams County | 6B | 6B | Insulation → |
| Bannock County | 6B | 6B | Insulation → |
| Bear Lake County | 6B | 6B | Insulation → |
| Benewah County | 5B | 5B | Insulation → |
| Bingham County | 6B | 6B | Insulation → |
| Blaine County | 6B | 6B | Insulation → |
| Boise County | 6B | 6B | Insulation → |
| Bonner County | 6B | 6B | Insulation → |
| Bonneville County | 6B | 6B | Insulation → |
| Boundary County | 6B | 6B | Insulation → |
| Butte County | 6B | 6B | Insulation → |
| Camas County | 6B | 6B | Insulation → |
| Canyon County | 5B | 5B | Insulation → |
| Caribou County | 6B | 6B | Insulation → |
| Cassia County | 5B | 5B | Insulation → |
| Clark County | 6B | 6B | Insulation → |
| Clearwater County | 5B | 5B | Insulation → |
| Custer County | 6B | 6B | Insulation → |
| Elmore County | 5B | 5B | Insulation → |
| Franklin County | 6B | 6B | Insulation → |
| Fremont County | 6B | 6B | Insulation → |
| Gem County | 5B | 5B | Insulation → |
| Gooding County | 5B | 5B | Insulation → |
| Idaho County | 5B | 5B | Insulation → |
| Jefferson County | 6B | 6B | Insulation → |
| Jerome County | 5B | 5B | Insulation → |
| Kootenai County | 5B | 5B | Insulation → |
| Latah County | 5B | 5B | Insulation → |
| Lemhi County | 6B | 6B | Insulation → |
| Lewis County | 5B | 5B | Insulation → |
| Lincoln County | 5B | 5B | Insulation → |
| Madison County | 6B | 6B | Insulation → |
| Minidoka County | 5B | 5B | Insulation → |
| Nez Perce County | 5B | 5B | Insulation → |
| Oneida County | 6B | 6B | Insulation → |
| Owyhee County | 5B | 5B | Insulation → |
| Payette County | 5B | 5B | Insulation → |
| Power County | 5B | 5B | Insulation → |
| Shoshone County | 5B | 5B | Insulation → |
| Teton County | 6B | 6B | Insulation → |
| Twin Falls County | 5B | 5B | Insulation → |
| Valley County | 6B | 6B | Insulation → |
| Washington 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 Idaho?
Idaho spans IECC climate zones 5B 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 Idaho?
The 2021 IECC calls for R-60 in the attic everywhere in Idaho.
What energy code does Idaho use?
Idaho enforces the 2018 IECC with amendments for homes (in effect since Jan 2021). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.
More for Idaho: Last frost dates in Idaho · Idaho planting zones · Frost line depth by state