Climate zones by state

Oregon Climate Zones by County

Oregon's 36 counties span climate zones 4C to 5B under the 2021 International Energy Conservation Code (IECC). Zone 5B is the most common, with 18 of the 36. For reference, Portland and Eugene are in zone 4C and Bend is in 5B.

Insulation minimums for each zone in Oregon

ZoneCountiesAtticWood-frame wallsFloors over unheated spaceBasement walls
4C18R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-30R-15ci, or R-19, or 13+5ci
5B18R-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 Oregon uses

Oregon enforces the 2023 Oregon Residential Specialty Code for homes (in effect since Oct 2023). 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

None of Oregon's counties changed zone between the 2018 and 2021 maps.

Every county in Oregon

NameZone (2021)Zone (2018)Details
Baker County5B5BInsulation →
Benton County4C4CInsulation →
Clackamas County4C4CInsulation →
Clatsop County4C4CInsulation →
Columbia County4C4CInsulation →
Coos County4C4CInsulation →
Crook County5B5BInsulation →
Curry County4C4CInsulation →
Deschutes County5B5BInsulation →
Douglas County4C4CInsulation →
Gilliam County5B5BInsulation →
Grant County5B5BInsulation →
Harney County5B5BInsulation →
Hood River County5B5BInsulation →
Jackson County4C4CInsulation →
Jefferson County5B5BInsulation →
Josephine County4C4CInsulation →
Klamath County5B5BInsulation →
Lake County5B5BInsulation →
Lane County4C4CInsulation →
Lincoln County4C4CInsulation →
Linn County4C4CInsulation →
Malheur County5B5BInsulation →
Marion County4C4CInsulation →
Morrow County5B5BInsulation →
Multnomah County4C4CInsulation →
Polk County4C4CInsulation →
Sherman County5B5BInsulation →
Tillamook County4C4CInsulation →
Umatilla County5B5BInsulation →
Union County5B5BInsulation →
Wallowa County5B5BInsulation →
Wasco County5B5BInsulation →
Washington County4C4CInsulation →
Wheeler County5B5BInsulation →
Yamhill County4C4CInsulation →

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 Oregon?

Oregon spans IECC climate zones 4C to 5B; zone 5B is the most common. Find your county in the table above, or search by ZIP code.

How much attic insulation do I need in Oregon?

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

What energy code does Oregon use?

Oregon enforces the 2023 Oregon Residential Specialty Code for homes (in effect since Oct 2023). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.

More for Oregon: Last frost dates in Oregon · Oregon planting zones · Frost line depth by state