Climate zones by state

Indiana Climate Zones by County

Indiana's 92 counties span climate zones 4A to 5A under the 2021 International Energy Conservation Code (IECC). Zone 5A is the most common, with 47 of the 92. For reference, Indianapolis and Evansville are in zone 4A and Fort Wayne is in 5A.

Insulation minimums for each zone in Indiana

ZoneCountiesAtticWood-frame wallsFloors over unheated spaceBasement walls
4A45R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-19R-10ci or R-13
5A47R-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 Indiana uses

Indiana enforces the 2018 IECC with amendments for homes (in effect since Dec 2019). 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

15 counties moved one zone warmer in the 2021 map: Bartholomew County (5 → 4), Clay County (5 → 4), Decatur County (5 → 4), Fayette County (5 → 4), Franklin County (5 → 4), Hendricks County (5 → 4), Johnson County (5 → 4), Marion County (5 → 4), Morgan County (5 → 4), Owen County (5 → 4), Putnam County (5 → 4), Rush County (5 → 4), and 3 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 Indiana

NameZone (2021)Zone (2018)Details
Adams County5A5AInsulation →
Allen County5A5AInsulation →
Bartholomew County4A5A changedInsulation →
Benton County5A5AInsulation →
Blackford County5A5AInsulation →
Boone County5A5AInsulation →
Brown County4A4AInsulation →
Carroll County5A5AInsulation →
Cass County5A5AInsulation →
Clark County4A4AInsulation →
Clay County4A5A changedInsulation →
Clinton County5A5AInsulation →
Crawford County4A4AInsulation →
Daviess County4A4AInsulation →
De Kalb County5A5AInsulation →
Dearborn County4A4AInsulation →
Decatur County4A5A changedInsulation →
Delaware County5A5AInsulation →
Dubois County4A4AInsulation →
Elkhart County5A5AInsulation →
Fayette County4A5A changedInsulation →
Floyd County4A4AInsulation →
Fountain County5A5AInsulation →
Franklin County4A5A changedInsulation →
Fulton County5A5AInsulation →
Gibson County4A4AInsulation →
Grant County5A5AInsulation →
Greene County4A4AInsulation →
Hamilton County5A5AInsulation →
Hancock County5A5AInsulation →
Harrison County4A4AInsulation →
Hendricks County4A5A changedInsulation →
Henry County5A5AInsulation →
Howard County5A5AInsulation →
Huntington County5A5AInsulation →
Jackson County4A4AInsulation →
Jasper County5A5AInsulation →
Jay County5A5AInsulation →
Jefferson County4A4AInsulation →
Jennings County4A4AInsulation →
Johnson County4A5A changedInsulation →
Knox County4A4AInsulation →
Kosciusko County5A5AInsulation →
La Porte County5A5AInsulation →
Lagrange County5A5AInsulation →
Lake County5A5AInsulation →
Lawrence County4A4AInsulation →
Madison County5A5AInsulation →
Marion County4A5A changedInsulation →
Marshall County5A5AInsulation →
Martin County4A4AInsulation →
Miami County5A5AInsulation →
Monroe County4A4AInsulation →
Montgomery County5A5AInsulation →
Morgan County4A5A changedInsulation →
Newton County5A5AInsulation →
Noble County5A5AInsulation →
Ohio County4A4AInsulation →
Orange County4A4AInsulation →
Owen County4A5A changedInsulation →
Parke County5A5AInsulation →
Perry County4A4AInsulation →
Pike County4A4AInsulation →
Porter County5A5AInsulation →
Posey County4A4AInsulation →
Pulaski County5A5AInsulation →
Putnam County4A5A changedInsulation →
Randolph County5A5AInsulation →
Ripley County4A4AInsulation →
Rush County4A5A changedInsulation →
Scott County4A4AInsulation →
Shelby County4A5A changedInsulation →
Spencer County4A4AInsulation →
St. Joseph County5A5AInsulation →
Starke County5A5AInsulation →
Steuben County5A5AInsulation →
Sullivan County4A4AInsulation →
Switzerland County4A4AInsulation →
Tippecanoe County5A5AInsulation →
Tipton County5A5AInsulation →
Union County4A5A changedInsulation →
Vanderburgh County4A4AInsulation →
Vermillion County5A5AInsulation →
Vigo County4A5A changedInsulation →
Wabash County5A5AInsulation →
Warren County5A5AInsulation →
Warrick County4A4AInsulation →
Washington County4A4AInsulation →
Wayne County5A5AInsulation →
Wells County5A5AInsulation →
White County5A5AInsulation →
Whitley County5A5AInsulation →

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 Indiana?

Indiana spans IECC climate zones 4A to 5A; 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 Indiana?

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

What energy code does Indiana use?

Indiana enforces the 2018 IECC with amendments for homes (in effect since Dec 2019). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.

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