Climate zones by state

Iowa Climate Zones by County

Iowa's 99 counties span climate zones 5A to 6A under the 2021 International Energy Conservation Code (IECC). Zone 5A is the most common, with 84 of the 99. For reference, Des Moines, Cedar Rapids and Davenport are in zone 5A.

Insulation minimums for each zone in Iowa

ZoneCountiesAtticWood-frame wallsFloors over unheated spaceBasement walls
5A84R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-30R-15ci, or R-19, or 13+5ci
6A15R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-30R-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 Iowa uses

Iowa enforces the 2012 IECC with amendments for homes (in effect since Jun 2014). 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

25 counties moved one zone warmer in the 2021 map: Allamakee County (6 → 5), Bremer County (6 → 5), Buchanan County (6 → 5), Buena Vista County (6 → 5), Butler County (6 → 5), Calhoun County (6 → 5), Cherokee County (6 → 5), Chickasaw County (6 → 5), Clayton County (6 → 5), Delaware County (6 → 5), Fayette County (6 → 5), Floyd County (6 → 5), and 13 more marked in the table below. If your town still enforces the 2018 or 2015 code, the older zone applies to permits.

Every county in Iowa

NameZone (2021)Zone (2018)Details
Adair County5A5AInsulation →
Adams County5A5AInsulation →
Allamakee County5A6A changedInsulation →
Appanoose County5A5AInsulation →
Audubon County5A5AInsulation →
Benton County5A5AInsulation →
Black Hawk County6A6AInsulation →
Boone County5A5AInsulation →
Bremer County5A6A changedInsulation →
Buchanan County5A6A changedInsulation →
Buena Vista County5A6A changedInsulation →
Butler County5A6A changedInsulation →
Calhoun County5A6A changedInsulation →
Carroll County5A5AInsulation →
Cass County5A5AInsulation →
Cedar County5A5AInsulation →
Cerro Gordo County6A6AInsulation →
Cherokee County5A6A changedInsulation →
Chickasaw County5A6A changedInsulation →
Clarke County5A5AInsulation →
Clay County6A6AInsulation →
Clayton County5A6A changedInsulation →
Clinton County5A5AInsulation →
Crawford County5A5AInsulation →
Dallas County5A5AInsulation →
Davis County5A5AInsulation →
Decatur County5A5AInsulation →
Delaware County5A6A changedInsulation →
Des Moines County5A5AInsulation →
Dickinson County6A6AInsulation →
Dubuque County5A5AInsulation →
Emmet County6A6AInsulation →
Fayette County5A6A changedInsulation →
Floyd County5A6A changedInsulation →
Franklin County5A6A changedInsulation →
Fremont County5A5AInsulation →
Greene County5A5AInsulation →
Grundy County5A6A changedInsulation →
Guthrie County5A5AInsulation →
Hamilton County5A6A changedInsulation →
Hancock County6A6AInsulation →
Hardin County5A6A changedInsulation →
Harrison County5A5AInsulation →
Henry County5A5AInsulation →
Howard County5A6A changedInsulation →
Humboldt County5A6A changedInsulation →
Ida County5A6A changedInsulation →
Iowa County5A5AInsulation →
Jackson County5A5AInsulation →
Jasper County5A5AInsulation →
Jefferson County5A5AInsulation →
Johnson County5A5AInsulation →
Jones County5A5AInsulation →
Keokuk County5A5AInsulation →
Kossuth County6A6AInsulation →
Lee County5A5AInsulation →
Linn County5A5AInsulation →
Louisa County5A5AInsulation →
Lucas County5A5AInsulation →
Lyon County6A6AInsulation →
Madison County5A5AInsulation →
Mahaska County5A5AInsulation →
Marion County5A5AInsulation →
Marshall County5A5AInsulation →
Mills County5A5AInsulation →
Mitchell County6A6AInsulation →
Monona County5A5AInsulation →
Monroe County5A5AInsulation →
Montgomery County5A5AInsulation →
Muscatine County5A5AInsulation →
O'Brien County6A6AInsulation →
Osceola County6A6AInsulation →
Page County5A5AInsulation →
Palo Alto County6A6AInsulation →
Plymouth County5A6A changedInsulation →
Pocahontas County5A6A changedInsulation →
Polk County5A5AInsulation →
Pottawattamie County5A5AInsulation →
Poweshiek County5A5AInsulation →
Ringgold County5A5AInsulation →
Sac County5A6A changedInsulation →
Scott County5A5AInsulation →
Shelby County5A5AInsulation →
Sioux County6A6AInsulation →
Story County5A5AInsulation →
Tama County5A5AInsulation →
Taylor County5A5AInsulation →
Union County5A5AInsulation →
Van Buren County5A5AInsulation →
Wapello County5A5AInsulation →
Warren County5A5AInsulation →
Washington County5A5AInsulation →
Wayne County5A5AInsulation →
Webster County5A6A changedInsulation →
Winnebago County6A6AInsulation →
Winneshiek County5A6A changedInsulation →
Woodbury County5A5AInsulation →
Worth County6A6AInsulation →
Wright County5A6A changedInsulation →

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 Iowa?

Iowa spans IECC climate zones 5A to 6A; zone 5A is the most common. Find your county in the table above, or search by ZIP code.

How much attic insulation do I need in Iowa?

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

What energy code does Iowa use?

Iowa enforces the 2012 IECC with amendments for homes (in effect since Jun 2014). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.

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