Insulation

Residential Energy Code by State

Which energy code each state and DC enforces for new homes and additions, as of September 2026. The most common is the 2021 IECC (11 states), and 9 states leave it to cities and counties.

Quick answer

Across the 50 states and DC, as of September 2026: 6 enforce the 2024 IECC, 11 the 2021 IECC (all with amendments), 9 the 2018 IECC, 7 the 2015 IECC and 6 an older edition. 9 states (Alaska, Arizona, Colorado, Kansas, Mississippi, Missouri, North Dakota, South Dakota and Wyoming) have no statewide code. California, Oregon and Washington write their own codes. Texas enforces the 2015 IECC.

Energy code by state

StateCode for homesIn effect sinceDOE rates it asComing next
Alabama2015 IECC with amendmentsOct 20162009 IECC–
AlaskaNo statewide code (home rule)–2009 IECC–
ArizonaNo statewide code (home rule)–2021 IECC–
Arkansas2009 IECC with amendmentsJan 2015Older than 2009 IECC–
California2025 Building Efficiency StandardsJan 20262024 IECC–
ColoradoNo statewide code (home rule)–2018 IECC–
Connecticut2021 IECC with amendmentsOct 20222021 IECC–
Delaware2024 IECCApr 20262024 IECC–
District of Columbia2015 IECC with amendmentsMay 20202018 IECC–
Florida2021 IECC with amendmentsDec 20232021 IECC–
Georgia2015 IECC with amendmentsJan 20202009 IECC–
Hawaii2018 IECC with amendments (local adoption varies)Dec 20202021 IECC–
Idaho2018 IECC with amendmentsJan 20212009 IECC–
Illinois2024 IECC with amendmentsNov 20252024 IECC–
Indiana2018 IECC with amendmentsDec 20192009 IECC–
Iowa2012 IECC with amendmentsJun 20142009 IECC–
KansasNo statewide code (home rule)–2018 IECC–
Kentucky2009 IECCOct 20142009 IECC–
Louisiana2021 IECC with amendmentsJul 20232018 IECC–
Maine2021 IECC with amendmentsApr 20252021 IECC–
Maryland2021 IECC with amendmentsMay 20232018 IECC–
Massachusetts2021 IECC with amendmentsOct 20242021 IECC–
Michigan2015 IECC with amendmentsFeb 20162009 IECC2021 IECC (delayed)
Minnesota2012 IECC with amendmentsFeb 20152009 IECC–
MississippiNo statewide code (home rule)–2009 IECC–
MissouriNo statewide code (home rule)–2015 IECC–
Montana2021 IECC with amendmentsJun 20222009 IECC–
Nebraska2018 IECCJul 20202018 IECC–
Nevada2024 IECC with amendments (local adoption varies)Aug 20242018 IECC–
New Hampshire2018 IECCJul 20222018 IECC–
New Jersey2024 IECCAug 20262024 IECC–
New Mexico2021 IECC with amendmentsJan 20242018 IECC–
New York2024 IECC with amendmentsDec 20252024 IECC–
North Carolina2015 IECC with amendmentsJan 20192009 IECC–
North DakotaNo statewide code (home rule)–2009 IECC–
Ohio2018 IECC with amendmentsJul 20192009 IECC–
Oklahoma2018 IECC with amendmentsSep 20222009 IECC2024 IRC, took effect Sep 2026 (DOE still lists it as upcoming)
Oregon2023 Oregon Residential Specialty CodeOct 20232018 IECC–
Pennsylvania2021 IECC with amendmentsJan 20262018 IECC–
Rhode Island2024 IECCDec 20252024 IECC–
South Carolina2009 IECCJan 20132009 IECC–
South DakotaNo statewide code (home rule)–2009 IECC–
Tennessee2018 IECC with amendmentsJul 20202009 IECC–
Texas2015 IECCSep 20162015 IECC–
Utah2021 IECC with amendmentsJul 20242009 IECC–
Vermont2018 IECC with amendmentsJul 20242021 IECC–
Virginia2021 IECC with amendmentsJan 20242018 IECC–
Washington2021 Washington State Energy CodeMar 20242024 IECC–
West Virginia2015 IECC with amendmentsAug 20222009 IECC–
Wisconsin2009 IECC with amendmentsJan 20162009 IECC–
WyomingNo statewide code (home rule)–2009 IECC–

Source: US Department of Energy Building Energy Codes Program, state residential code status (September 2026). "DOE rates it as" is DOE's estimate of which IECC edition the state's code is equivalent to in energy use; amendments can make a newer code perform like an older one. Cities may enforce a newer code than their state.

Home-rule states

Alaska, Arizona, Colorado, Kansas, Mississippi, Missouri, North Dakota, South Dakota and Wyoming don't set one energy code for the whole state. Each city or county adopts its own, so two towns a few miles apart can have different insulation rules. DOE's rating for these states reflects a typical local code, not a statewide rule. Call the local building department before you buy materials for a permitted job.

What it means for your project

  • Your climate zone sets the insulation levels, and your code edition sets which table applies. Look up both with our climate zone lookup.
  • The R-value chart shows the 2021 and 2018 tables side by side.
  • Codes apply to new homes, additions and most permitted remodels. Topping up attic insulation in your own home usually doesn't need a permit, but the code levels are a sensible target.

Frequently asked questions

What energy code does my state use?

Find your state in the table. Most states adopt a version of the International Energy Conservation Code (IECC), often with their own amendments. California, Oregon and Washington write their own codes. In home-rule states there is no statewide code, so each city or county decides.

What is the difference between the IECC and the IRC energy chapter?

The International Residential Code (IRC) includes the residential energy rules as its Chapter 11, which matches the IECC residential provisions for the same edition. A state that adopts the 2021 IRC usually gets the 2021 energy requirements with it, unless it amends that chapter.

Why do the insulation rules on this site show 2021 values if my state uses an older code?

Our R-value tables use the 2021 IECC, the edition most states are on or moving to, with the 2018 values beside it. The 2024 IECC is newer, and six states enforce it. For a permit, the edition your state or city adopted is what counts.

Last reviewed 2026-10-21.