Insulation Requirements by State
Every US state falls within one or more DOE climate zones, which determine the recommended insulation R-values for residential and commercial buildings. Many states span multiple zones due to variations in elevation, latitude, and proximity to large bodies of water. Use the table below to find your state and see which climate zones apply. Click on any state for detailed insulation recommendations specific to your location.
State Climate Zone Directory
The table lists all 50 US states plus the District of Columbia with their applicable DOE climate zones. States that span multiple zones show all applicable zones. Remember that insulation requirements are determined by your specific county location, not the state as a whole. For states spanning multiple zones, check your county on the DOE ZIP code lookup tool or on your state's energy code documentation to determine the exact zone for your building site.
| State | Abbr. | Climate Zones | Attic R-Value Range |
|---|---|---|---|
| Alabama | AL | Zone 2, Zone 3 | R-38 |
| Alaska | AK | Zone 7, Zone 8 | R-60 |
| Arizona | AZ | Zone 2, Zone 3, Zone 4, Zone 5 | R-38 to R-49 |
| Arkansas | AR | Zone 3, Zone 4 | R-38 to R-49 |
| California | CA | Zone 3, Zone 4, Zone 5 | R-38 to R-49 |
| Colorado | CO | Zone 5, Zone 6, Zone 7 | R-49 to R-60 |
| Connecticut | CT | Zone 5, Zone 6 | R-49 to R-60 |
| Delaware | DE | Zone 4 | R-49 |
| District of Columbia | DC | Zone 4 | R-49 |
| Florida | FL | Zone 1, Zone 2 | R-30 to R-38 |
| Georgia | GA | Zone 2, Zone 3, Zone 4 | R-38 to R-49 |
| Hawaii | HI | Zone 1 | R-30 |
| Idaho | ID | Zone 5, Zone 6 | R-49 to R-60 |
| Illinois | IL | Zone 4, Zone 5 | R-49 |
| Indiana | IN | Zone 4, Zone 5 | R-49 |
| Iowa | IA | Zone 5, Zone 6 | R-49 to R-60 |
| Kansas | KS | Zone 4, Zone 5 | R-49 |
| Kentucky | KY | Zone 4 | R-49 |
| Louisiana | LA | Zone 2, Zone 3 | R-38 |
| Maine | ME | Zone 6, Zone 7 | R-60 |
| Maryland | MD | Zone 4, Zone 5 | R-49 |
| Massachusetts | MA | Zone 5, Zone 6 | R-49 to R-60 |
| Michigan | MI | Zone 5, Zone 6 | R-49 to R-60 |
| Minnesota | MN | Zone 6, Zone 7 | R-60 |
| Mississippi | MS | Zone 2, Zone 3 | R-38 |
| Missouri | MO | Zone 4, Zone 5 | R-49 |
| Montana | MT | Zone 6, Zone 7 | R-60 |
| Nebraska | NE | Zone 5, Zone 6 | R-49 to R-60 |
| Nevada | NV | Zone 3, Zone 4, Zone 5 | R-38 to R-49 |
| New Hampshire | NH | Zone 5, Zone 6 | R-49 to R-60 |
| New Jersey | NJ | Zone 4, Zone 5 | R-49 |
| New Mexico | NM | Zone 3, Zone 4, Zone 5 | R-38 to R-49 |
| New York | NY | Zone 4, Zone 5, Zone 6 | R-49 to R-60 |
| North Carolina | NC | Zone 3, Zone 4, Zone 5 | R-38 to R-49 |
| North Dakota | ND | Zone 6, Zone 7 | R-60 |
| Ohio | OH | Zone 4, Zone 5 | R-49 |
| Oklahoma | OK | Zone 3, Zone 4 | R-38 to R-49 |
| Oregon | OR | Zone 4, Zone 5 | R-49 |
| Pennsylvania | PA | Zone 4, Zone 5, Zone 6 | R-49 to R-60 |
| Rhode Island | RI | Zone 5 | R-49 |
| South Carolina | SC | Zone 3 | R-38 |
| South Dakota | SD | Zone 5, Zone 6 | R-49 to R-60 |
| Tennessee | TN | Zone 3, Zone 4 | R-38 to R-49 |
| Texas | TX | Zone 2, Zone 3, Zone 4 | R-38 to R-49 |
| Utah | UT | Zone 4, Zone 5, Zone 6 | R-49 to R-60 |
| Vermont | VT | Zone 6 | R-60 |
| Virginia | VA | Zone 3, Zone 4, Zone 5 | R-38 to R-49 |
| Washington | WA | Zone 4, Zone 5 | R-49 |
| West Virginia | WV | Zone 4, Zone 5 | R-49 |
| Wisconsin | WI | Zone 5, Zone 6, Zone 7 | R-49 to R-60 |
| Wyoming | WY | Zone 6, Zone 7 | R-60 |
Understanding State Insulation Requirements
Insulation requirements in the United States are established through a combination of federal recommendations and state-adopted building codes. The DOE publishes recommended R-values for each climate zone, and these recommendations are incorporated into the International Energy Conservation Code (IECC). Each state then adopts the IECC in whole or with amendments, creating state-specific energy code requirements that may differ from the base DOE recommendations.
Some states have adopted the most recent version of the IECC and enforce insulation requirements that match or exceed the DOE recommendations. Other states may be several editions behind, with insulation requirements that are lower than current best practices. A few states, particularly in the southern United States, have historically adopted less stringent energy codes. Conversely, states like California, Massachusetts, and Washington have energy codes that significantly exceed the national model code.
Beyond state energy codes, many municipalities and counties adopt their own amendments or more stringent requirements. For example, cities with green building ordinances may require insulation levels above the state minimum. Some jurisdictions offer expedited permitting or fee reductions for projects that exceed code minimum insulation levels. Additionally, utility rebate programs and federal tax credits often incentivize insulation improvements that go beyond code requirements, making it financially advantageous to install more insulation than the minimum required.
When planning an insulation project, always verify your local code requirements with the building department having jurisdiction over your project. The R-values shown in this calculator represent DOE recommendations, which serve as a baseline. Your local requirements may be higher, and exceeding both the code minimum and the DOE recommendations is always acceptable and often provides the best return on investment in terms of energy savings, comfort, and long-term property value.