Vermont Climate Zones by County
All 14 of Vermont's counties are in climate zone 6A under the 2021 International Energy Conservation Code (IECC).
Insulation minimums in Vermont (zone 6A)
| Zone | Attic | Wood-frame walls | Floors over unheated space | Basement walls |
|---|---|---|---|---|
| 6A | 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 Vermont uses
Vermont enforces the 2018 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
None of Vermont's counties changed zone between the 2018 and 2021 maps.
Every county in Vermont
| Name | Zone (2021) | Zone (2018) | Details |
|---|---|---|---|
| Addison County | 6A | 6A | Insulation → |
| Bennington County | 6A | 6A | Insulation → |
| Caledonia County | 6A | 6A | Insulation → |
| Chittenden County | 6A | 6A | Insulation → |
| Essex County | 6A | 6A | Insulation → |
| Franklin County | 6A | 6A | Insulation → |
| Grand Isle County | 6A | 6A | Insulation → |
| Lamoille County | 6A | 6A | Insulation → |
| Orange County | 6A | 6A | Insulation → |
| Orleans County | 6A | 6A | Insulation → |
| Rutland County | 6A | 6A | Insulation → |
| Washington County | 6A | 6A | Insulation → |
| Windham County | 6A | 6A | Insulation → |
| Windsor 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 Vermont?
Vermont is IECC climate zone 6A under the 2021 code.
How much attic insulation do I need in Vermont?
The 2021 IECC calls for R-60 in the attic everywhere in Vermont.
What energy code does Vermont use?
Vermont enforces the 2018 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.
More for Vermont: Last frost dates in Vermont · Vermont planting zones · Frost line depth by state