Climate zones by state

Michigan Climate Zones by County

Michigan's 83 counties span climate zones 5A to 7 under the 2021 International Energy Conservation Code (IECC). Zone 6A is the most common, with 44 of the 83. For reference, Detroit and Grand Rapids are in zone 5A and Marquette is in 7.

Insulation minimums for each zone in Michigan

ZoneCountiesAtticWood-frame wallsFloors over unheated spaceBasement walls
5A37R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-30R-15ci, or R-19, or 13+5ci
6A44R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-30R-15ci, or R-19, or 13+5ci
72R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-38R-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 Michigan uses

Michigan enforces the 2015 IECC with amendments for homes (in effect since Feb 2016). Next: 2021 IECC (delayed). 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

In the 2021 map, 11 moved warmer and one moved colder: Baraga County (7 → 6), Chippewa County (7 → 6), Gogebic County (7 → 6), Houghton County (7 → 6), Huron County (6 → 5), Iron County (7 → 6), Luce County (7 → 6), Mackinac County (7 → 6), Marquette County (6 → 7), Ontonagon County (7 → 6), Sanilac County (6 → 5), Schoolcraft County (7 → 6). If your town still enforces the 2018 or 2015 code, the older zone applies to permits.

Every county in Michigan

NameZone (2021)Zone (2018)Details
Alcona County6A6AInsulation →
Alger County6A6AInsulation →
Allegan County5A5AInsulation →
Alpena County6A6AInsulation →
Antrim County6A6AInsulation →
Arenac County6A6AInsulation →
Baraga County6A7 changedInsulation →
Barry County5A5AInsulation →
Bay County5A5AInsulation →
Benzie County6A6AInsulation →
Berrien County5A5AInsulation →
Branch County5A5AInsulation →
Calhoun County5A5AInsulation →
Cass County5A5AInsulation →
Charlevoix County6A6AInsulation →
Cheboygan County6A6AInsulation →
Chippewa County6A7 changedInsulation →
Clare County6A6AInsulation →
Clinton County5A5AInsulation →
Crawford County6A6AInsulation →
Delta County6A6AInsulation →
Dickinson County6A6AInsulation →
Eaton County5A5AInsulation →
Emmet County6A6AInsulation →
Genesee County5A5AInsulation →
Gladwin County6A6AInsulation →
Gogebic County6A7 changedInsulation →
Grand Traverse County6A6AInsulation →
Gratiot County5A5AInsulation →
Hillsdale County5A5AInsulation →
Houghton County6A7 changedInsulation →
Huron County5A6A changedInsulation →
Ingham County5A5AInsulation →
Ionia County5A5AInsulation →
Iosco County6A6AInsulation →
Iron County6A7 changedInsulation →
Isabella County6A6AInsulation →
Jackson County5A5AInsulation →
Kalamazoo County5A5AInsulation →
Kalkaska County6A6AInsulation →
Kent County5A5AInsulation →
Keweenaw County77Insulation →
Lake County6A6AInsulation →
Lapeer County5A5AInsulation →
Leelanau County6A6AInsulation →
Lenawee County5A5AInsulation →
Livingston County5A5AInsulation →
Luce County6A7 changedInsulation →
Mackinac County6A7 changedInsulation →
Macomb County5A5AInsulation →
Manistee County6A6AInsulation →
Marquette County76 changedInsulation →
Mason County6A6AInsulation →
Mecosta County6A6AInsulation →
Menominee County6A6AInsulation →
Midland County5A5AInsulation →
Missaukee County6A6AInsulation →
Monroe County5A5AInsulation →
Montcalm County5A5AInsulation →
Montmorency County6A6AInsulation →
Muskegon County5A5AInsulation →
Newaygo County6A6AInsulation →
Oakland County5A5AInsulation →
Oceana County6A6AInsulation →
Ogemaw County6A6AInsulation →
Ontonagon County6A7 changedInsulation →
Osceola County6A6AInsulation →
Oscoda County6A6AInsulation →
Otsego County6A6AInsulation →
Ottawa County5A5AInsulation →
Presque Isle County6A6AInsulation →
Roscommon County6A6AInsulation →
Saginaw County5A5AInsulation →
Sanilac County5A6A changedInsulation →
Schoolcraft County6A7 changedInsulation →
Shiawassee County5A5AInsulation →
St. Clair County5A5AInsulation →
St. Joseph County5A5AInsulation →
Tuscola County5A5AInsulation →
Van Buren County5A5AInsulation →
Washtenaw County5A5AInsulation →
Wayne County5A5AInsulation →
Wexford County6A6AInsulation →

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 Michigan?

Michigan spans IECC climate zones 5A 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 Michigan?

The 2021 IECC calls for R-60 in the attic everywhere in Michigan.

What energy code does Michigan use?

Michigan enforces the 2015 IECC with amendments for homes (in effect since Feb 2016). Next: 2021 IECC (delayed). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.

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