MUBEC only draws one line through the state: Aroostook County versus everywhere else. In practice, elevation, wind exposure, and distance from the coast create real differences in how much insulation makes sense from Kittery to Fort Kent. Click a region on the map for a working recommendation.
Officially, Maine's energy code recognizes two IECC climate zones — Zone 7 in Aroostook County and Zone 6 everywhere else. That's the legal minimum described on the MUBEC codes page. But builders and energy auditors working across the state routinely treat a handful of sub-regions differently in practice, because two homes in the same code zone can face very different winters depending on elevation, wind exposure, and how much the coast moderates the cold.
The map groups Maine into six practical regions along those lines. Click or tap a region to see its official MUBEC zone, the code's prescriptive insulation targets, and the on-the-ground considerations worth factoring into a mobile home retrofit there.
| Region | Counties | MUBEC zone | Ceiling | Floor | Practical note |
|---|---|---|---|---|---|
| Aroostook | Aroostook | 7 | R-60 | R-38 | Maine's only Zone 7 county — the coldest design temperatures and the highest floor-insulation target in the state. |
| North Woods & Interior | N. Piscataquis, N. Somerset, N. Penobscot | 6 | R-60 | R-30 | Zone 6 on the map, but remote interior valleys see Zone 7‑like cold snaps; many auditors target the top of the Zone 6 range here. |
| Western Mountains | Oxford, Franklin | 6 | R-60 | R-30 | High-elevation valleys (Rangeley, Bethel) rank among the coldest recorded temperatures outside Aroostook; ridge wind adds to air-sealing priority. |
| Downeast & Washington | Hancock, Washington | 6 | R-60 | R-30 | Coastal moderation helps average temperatures, but near-constant wind off the water drives infiltration heat loss — air sealing matters as much as R-value. |
| Central & Midcoast | Kennebec, Androscoggin, Waldo, Knox, Lincoln, S. Penobscot | 6 | R-60 | R-30 | The most typical Zone 6 conditions in the state; river valleys can pool cold air overnight. |
| Southern & Coastal | York, Cumberland, Sagadahoc | 6 | R-60 | R-30 | Mildest part of Maine, but still solidly Zone 6 — meaningfully colder than coastal areas just a few hours south. |
Wall target for all regions: R-20 + R-5 continuous insulation, or R-13 + R-10 continuous insulation, per MUBEC's 2021 IECC adoption. See the MUBEC codes page for the full prescriptive table and how it applies to manufactured housing specifically.
See which of these targets Efficiency Maine's rebate program will help pay for.