Climate zones by state

Ohio Climate Zones by County

Ohio's 88 counties span climate zones 4A to 5A under the 2021 International Energy Conservation Code (IECC). Zone 5A is the most common, with 64 of the 88. For reference, Cincinnati and Columbus are in zone 4A and Cleveland is in 5A.

Insulation minimums for each zone in Ohio

ZoneCountiesAtticWood-frame wallsFloors over unheated spaceBasement walls
4A24R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-19R-10ci or R-13
5A64R-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 Ohio uses

Ohio enforces the 2018 IECC with amendments for homes (in effect since Jul 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: Athens County (5 → 4), Butler County (5 → 4), Clinton County (5 → 4), Fayette County (5 → 4), Franklin County (5 → 4), Greene County (5 → 4), Highland County (5 → 4), Hocking County (5 → 4), Jackson County (5 → 4), Madison County (5 → 4), Meigs County (5 → 4), Pickaway 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 Ohio

NameZone (2021)Zone (2018)Details
Adams County4A4AInsulation →
Allen County5A5AInsulation →
Ashland County5A5AInsulation →
Ashtabula County5A5AInsulation →
Athens County4A5A changedInsulation →
Auglaize County5A5AInsulation →
Belmont County5A5AInsulation →
Brown County4A4AInsulation →
Butler County4A5A changedInsulation →
Carroll County5A5AInsulation →
Champaign County5A5AInsulation →
Clark County5A5AInsulation →
Clermont County4A4AInsulation →
Clinton County4A5A changedInsulation →
Columbiana County5A5AInsulation →
Coshocton County5A5AInsulation →
Crawford County5A5AInsulation →
Cuyahoga County5A5AInsulation →
Darke County5A5AInsulation →
Defiance County5A5AInsulation →
Delaware County5A5AInsulation →
Erie County5A5AInsulation →
Fairfield County5A5AInsulation →
Fayette County4A5A changedInsulation →
Franklin County4A5A changedInsulation →
Fulton County5A5AInsulation →
Gallia County4A4AInsulation →
Geauga County5A5AInsulation →
Greene County4A5A changedInsulation →
Guernsey County5A5AInsulation →
Hamilton County4A4AInsulation →
Hancock County5A5AInsulation →
Hardin County5A5AInsulation →
Harrison County5A5AInsulation →
Henry County5A5AInsulation →
Highland County4A5A changedInsulation →
Hocking County4A5A changedInsulation →
Holmes County5A5AInsulation →
Huron County5A5AInsulation →
Jackson County4A5A changedInsulation →
Jefferson County5A5AInsulation →
Knox County5A5AInsulation →
Lake County5A5AInsulation →
Lawrence County4A4AInsulation →
Licking County5A5AInsulation →
Logan County5A5AInsulation →
Lorain County5A5AInsulation →
Lucas County5A5AInsulation →
Madison County4A5A changedInsulation →
Mahoning County5A5AInsulation →
Marion County5A5AInsulation →
Medina County5A5AInsulation →
Meigs County4A5A changedInsulation →
Mercer County5A5AInsulation →
Miami County5A5AInsulation →
Monroe County5A5AInsulation →
Montgomery County5A5AInsulation →
Morgan County5A5AInsulation →
Morrow County5A5AInsulation →
Muskingum County5A5AInsulation →
Noble County5A5AInsulation →
Ottawa County5A5AInsulation →
Paulding County5A5AInsulation →
Perry County5A5AInsulation →
Pickaway County4A5A changedInsulation →
Pike County4A4AInsulation →
Portage County5A5AInsulation →
Preble County5A5AInsulation →
Putnam County5A5AInsulation →
Richland County5A5AInsulation →
Ross County4A5A changedInsulation →
Sandusky County5A5AInsulation →
Scioto County4A4AInsulation →
Seneca County5A5AInsulation →
Shelby County5A5AInsulation →
Stark County5A5AInsulation →
Summit County5A5AInsulation →
Trumbull County5A5AInsulation →
Tuscarawas County5A5AInsulation →
Union County5A5AInsulation →
Van Wert County5A5AInsulation →
Vinton County4A5A changedInsulation →
Warren County4A5A changedInsulation →
Washington County4A4AInsulation →
Wayne County5A5AInsulation →
Williams County5A5AInsulation →
Wood County5A5AInsulation →
Wyandot 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 Ohio?

Ohio 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 Ohio?

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

What energy code does Ohio use?

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

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