DOE Climate Zone R-Value Reference
The U.S. Department of Energy divides the country into 8 climate zones. Your climate zone determines the recommended R-value for attic, wall, floor, and crawl space insulation. Use the table below to find your zone, then see the recommended R-values — verified from ENERGY STAR / U.S. DOE as of June 2026.
DOE Climate Zone Descriptions
| Zone | Climate Type | Example States / Areas | Recommended Attic R-value |
|---|---|---|---|
| Zone 1 | Very Hot — Humid | Hawaii, Guam, Puerto Rico, south FL | R-30 |
| Zone 2 | Hot — Humid | South TX, south AZ, southern FL, LA | R-30–49 |
| Zone 3 | Warm — Humid / Dry | CA, NV, TX, GA, AR, MS, OK | R-30–49 |
| Zone 4 | Mixed — Humid / Dry | VA, TN, OR, KY, KS, MO, UT, MD | R-38–60 |
| Zone 5 | Cool — Humid / Dry | CO, IL, OH, PA, MA, RI, IN, NE | R-49–60 |
| Zone 6 | Cold | MN, MT, VT, ME, NH, WI, MI | R-49–60 |
| Zone 7 | Very Cold | Northern MN, northern MT, ND, SD, WY | R-49–60 |
| Zone 8 | Subarctic / Arctic | Alaska | R-49–60 |
Source: ENERGY STAR / U.S. DOE — as of June 2026. Recommendations are for existing-home upgrades (unfinished attic, gas or electric heat).
Recommended R-Values by Zone and Location
The table below shows DOE recommended R-value ranges for attic, exterior walls, and floors/crawl spaces. These are cost-effectiveness recommendations for existing homes, not minimum code requirements for new construction.
| Zone | Attic / Ceiling | Exterior Wall | Floor / Crawl Space |
|---|---|---|---|
| Zone 1 | R-30 | R-13 | R-13 |
| Zone 2 | R-30–49 | R-13–15 | R-13–19 |
| Zone 3 | R-30–49 | R-13–15 | R-19–25 |
| Zone 4 | R-38–60 | R-13–21 | R-25–30 |
| Zone 5 | R-49–60 | R-13–21 | R-25–30 |
| Zone 6 | R-49–60 | R-15–21 | R-25–30 |
| Zone 7 | R-49–60 | R-18–21+ | R-25–30 |
| Zone 8 | R-49–60 | R-18–21+ | R-25–30 |
Wall values are for cavity insulation only. In Zones 4–8, adding continuous insulation (CI) to the exterior is recommended for full code compliance. Always verify with your local building department and energy.gov.
State Climate Zone Reference
The table below lists the primary climate zone for each U.S. state. Many states span two or more zones — look up your specific county on the DOE energy saver page or the IECC 2021 climate zone tables for an exact answer.
| State | Primary Zone(s) |
|---|---|
| Alabama | Zone 3 |
| Alaska | Zone 8 |
| Arizona | Zone 3 |
| Arkansas | Zone 3 |
| California | Zone 3–5 |
| Colorado | Zone 5–6 |
| Connecticut | Zone 5 |
| Delaware | Zone 4 |
| Florida | Zone 1–2 |
| Georgia | Zone 3 |
| Hawaii | Zone 1 |
| Idaho | Zone 5–6 |
| Illinois | Zone 5–6 |
| Indiana | Zone 5 |
| Iowa | Zone 5–6 |
| Kansas | Zone 4 |
| Kentucky | Zone 4 |
| Louisiana | Zone 2 |
| Maine | Zone 6 |
| Maryland | Zone 4 |
| Massachusetts | Zone 5 |
| Michigan | Zone 5–6 |
| Minnesota | Zone 6–7 |
| Mississippi | Zone 3 |
| Missouri | Zone 4 |
| Montana | Zone 6–7 |
| Nebraska | Zone 5–6 |
| Nevada | Zone 3–5 |
| New Hampshire | Zone 6 |
| New Jersey | Zone 4 |
| New Mexico | Zone 3–5 |
| New York | Zone 4–6 |
| North Carolina | Zone 3–4 |
| North Dakota | Zone 6–7 |
| Ohio | Zone 5 |
| Oklahoma | Zone 3 |
| Oregon | Zone 4–5 |
| Pennsylvania | Zone 4–5 |
| Rhode Island | Zone 5 |
| South Carolina | Zone 3 |
| South Dakota | Zone 6–7 |
| Tennessee | Zone 4 |
| Texas | Zone 2–4 |
| Utah | Zone 4–5 |
| Vermont | Zone 6 |
| Virginia | Zone 4–5 |
| Washington | Zone 4–5 |
| West Virginia | Zone 5 |
| Wisconsin | Zone 6–7 |
| Wyoming | Zone 6–7 |
How to Use Your Climate Zone
Once you know your climate zone, use our calculators to determine how much insulation to add:
- Insulation Calculator — enter zone, area, existing R-value to get depth + bags
- Attic Insulation Calculator
- Blown-In Insulation Calculator
- R-Value Calculator — lookup by zone and location
- Spray Foam Calculator
Frequently Asked Questions
The U.S. Department of Energy divides the country into 8 climate zones (plus a marine sub-zone) based on heating and cooling degree days. Zone 1 is the hottest; Zone 8 is the coldest (subarctic Alaska). These zones are used to determine minimum and recommended R-values for insulation in residential buildings.
The most precise way is to use the DOE's interactive climate zone map at energy.gov or look up your county in the IECC 2021 climate zone lookup. The state table on this page gives the most common zone for each state, but many states span two or more zones.
Yes. Zone 4C (marine) covers parts of the Pacific Northwest (western Washington and Oregon). It has a mild, wet climate distinct from Zone 4A (mixed humid, mid-Atlantic and Tennessee) and Zone 4B (mixed dry, interior West). R-value recommendations are similar but moisture management strategies differ.
The ENERGY STAR recommendations are primarily for existing-home upgrades. New construction follows IECC code minimums, which may differ. New homes in many zones are required to meet higher standards than the DOE cost-effective recommendations for retrofits.