Maine Climate Zones by County
Maine's 16 counties span climate zones 6A to 7 under the 2021 International Energy Conservation Code (IECC). Zone 6A is the most common, with 15 of the 16. For reference, Portland and Bangor are in zone 6A and Presque Isle is in 7.
Insulation minimums for each zone in Maine
| Zone | Counties | Attic | Wood-frame walls | Floors over unheated space | Basement walls |
|---|---|---|---|---|---|
| 6A | 15 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-30 | R-15ci, or R-19, or 13+5ci |
| 7 | 1 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-38 | 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 Maine uses
Maine enforces the 2021 IECC with amendments for homes (in effect since Apr 2025). 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 Maine's counties changed zone between the 2018 and 2021 maps.
Every county in Maine
| Name | Zone (2021) | Zone (2018) | Details |
|---|---|---|---|
| Androscoggin County | 6A | 6A | Insulation → |
| Aroostook County | 7 | 7 | Insulation → |
| Cumberland County | 6A | 6A | Insulation → |
| Franklin County | 6A | 6A | Insulation → |
| Hancock County | 6A | 6A | Insulation → |
| Kennebec County | 6A | 6A | Insulation → |
| Knox County | 6A | 6A | Insulation → |
| Lincoln County | 6A | 6A | Insulation → |
| Oxford County | 6A | 6A | Insulation → |
| Penobscot County | 6A | 6A | Insulation → |
| Piscataquis County | 6A | 6A | Insulation → |
| Sagadahoc County | 6A | 6A | Insulation → |
| Somerset County | 6A | 6A | Insulation → |
| Waldo County | 6A | 6A | Insulation → |
| Washington County | 6A | 6A | Insulation → |
| York County | 6A | 6A | 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 Maine?
Maine spans IECC climate zones 6A to 7; zone 6A is the most common. Find your county in the table above, or search by ZIP code.
How much attic insulation do I need in Maine?
The 2021 IECC calls for R-60 in the attic everywhere in Maine.
What energy code does Maine use?
Maine enforces the 2021 IECC with amendments for homes (in effect since Apr 2025). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.
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