Climate zones by state

Tennessee Climate Zones by County

Tennessee's 95 counties span climate zones 3A to 4A under the 2021 International Energy Conservation Code (IECC). Zone 4A is the most common, with 61 of the 95. For reference, Memphis and Nashville are in zone 3A and Knoxville is in 4A.

Insulation minimums for each zone in Tennessee

ZoneCountiesAtticWood-frame wallsFloors over unheated spaceBasement walls
3A34R-49R-20, or 13+5ci, or R-15ciR-19R-5ci or R-13
4A61R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-19R-10ci or R-13

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 Tennessee uses

Tennessee enforces the 2018 IECC with amendments for homes (in effect since Jul 2020). 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, 21 moved warmer and one moved colder: Bedford County (4 → 3), Coffee County (4 → 3), Davidson County (4 → 3), Decatur County (4 → 3), Franklin County (4 → 3), Gibson County (4 → 3), Giles County (4 → 3), Grundy County (4 → 3), Hamilton County (4 → 3), Hickman County (4 → 3), Lake County (3 → 4), Lawrence County (4 → 3), and 10 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 Tennessee

NameZone (2021)Zone (2018)Details
Anderson County4A4AInsulation →
Bedford County3A4A changedInsulation →
Benton County4A4AInsulation →
Bledsoe County4A4AInsulation →
Blount County4A4AInsulation →
Bradley County4A4AInsulation →
Campbell County4A4AInsulation →
Cannon County4A4AInsulation →
Carroll County4A4AInsulation →
Carter County4A4AInsulation →
Cheatham County4A4AInsulation →
Chester County3A3AInsulation →
Claiborne County4A4AInsulation →
Clay County4A4AInsulation →
Cocke County4A4AInsulation →
Coffee County3A4A changedInsulation →
Crockett County3A3AInsulation →
Cumberland County4A4AInsulation →
Davidson County3A4A changedInsulation →
Decatur County3A4A changedInsulation →
DeKalb County4A4AInsulation →
Dickson County4A4AInsulation →
Dyer County3A3AInsulation →
Fayette County3A3AInsulation →
Fentress County4A4AInsulation →
Franklin County3A4A changedInsulation →
Gibson County3A4A changedInsulation →
Giles County3A4A changedInsulation →
Grainger County4A4AInsulation →
Greene County4A4AInsulation →
Grundy County3A4A changedInsulation →
Hamblen County4A4AInsulation →
Hamilton County3A4A changedInsulation →
Hancock County4A4AInsulation →
Hardeman County3A3AInsulation →
Hardin County3A3AInsulation →
Hawkins County4A4AInsulation →
Haywood County3A3AInsulation →
Henderson County3A3AInsulation →
Henry County4A4AInsulation →
Hickman County3A4A changedInsulation →
Houston County4A4AInsulation →
Humphreys County4A4AInsulation →
Jackson County4A4AInsulation →
Jefferson County4A4AInsulation →
Johnson County4A4AInsulation →
Knox County4A4AInsulation →
Lake County4A3A changedInsulation →
Lauderdale County3A3AInsulation →
Lawrence County3A4A changedInsulation →
Lewis County3A4A changedInsulation →
Lincoln County3A4A changedInsulation →
Loudon County4A4AInsulation →
Macon County4A4AInsulation →
Madison County3A3AInsulation →
Marion County3A4A changedInsulation →
Marshall County3A4A changedInsulation →
Maury County3A4A changedInsulation →
McMinn County4A4AInsulation →
McNairy County3A3AInsulation →
Meigs County4A4AInsulation →
Monroe County4A4AInsulation →
Montgomery County4A4AInsulation →
Moore County3A4A changedInsulation →
Morgan County4A4AInsulation →
Obion County4A4AInsulation →
Overton County4A4AInsulation →
Perry County3A4A changedInsulation →
Pickett County4A4AInsulation →
Polk County4A4AInsulation →
Putnam County4A4AInsulation →
Rhea County4A4AInsulation →
Roane County4A4AInsulation →
Robertson County4A4AInsulation →
Rutherford County3A4A changedInsulation →
Scott County4A4AInsulation →
Sequatchie County4A4AInsulation →
Sevier County4A4AInsulation →
Shelby County3A3AInsulation →
Smith County4A4AInsulation →
Stewart County4A4AInsulation →
Sullivan County4A4AInsulation →
Sumner County4A4AInsulation →
Tipton County3A3AInsulation →
Trousdale County4A4AInsulation →
Unicoi County4A4AInsulation →
Union County4A4AInsulation →
Van Buren County4A4AInsulation →
Warren County4A4AInsulation →
Washington County4A4AInsulation →
Wayne County3A4A changedInsulation →
Weakley County4A4AInsulation →
White County4A4AInsulation →
Williamson County3A4A changedInsulation →
Wilson County4A4AInsulation →

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 Tennessee?

Tennessee spans IECC climate zones 3A to 4A; zone 4A is the most common. Find your county in the table above, or search by ZIP code.

How much attic insulation do I need in Tennessee?

In Tennessee, the 2021 IECC calls for R-49 and R-60 in the attic, depending on the zone. The table near the top of this page lists each zone's minimums.

What energy code does Tennessee use?

Tennessee enforces the 2018 IECC with amendments for homes (in effect since Jul 2020). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.

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