Washington enforces the 2021 IECC residential

Record of adoption

In force since

Mar 15, 2024

Legal citation

WAC 51-11R-10100; chapter 19.27A RCW (RCW 19.27A.045)

Adopted by

Washington State Building Code Council

Second reading

Agreed Oct 18, 2026

Applies

Statewide

State amendments

Major

Also called

WSEC-R, WAC 51-11R, 2021 WSEC residential

The WAC chapter title names the 2021 IECC. The state code is the Washington State Energy Code (WSEC-R) with Washington amendments (DOE also says ‘with state amendments’), including EPCA-related changes in WSR 24-03-084 that took effect with the code. The state amendments are rated substantial because Washington rewrites the IECC into its own WSEC chapter. WAC history shows no later amendment. The Council ended its I-2066 rulemaking on Apr 25, 2025, without amending the 2021 WSEC.

Coming next

• 2024 IECCPartial
  Planned for May 3, 2027ProposedWAC 51-11R (CR-102 filed Jul 1, 2026)

  Public hearings Aug 5, 2026, and Aug 7, 2026. The CR-102 listed Sep 25, 2026, as intended adoption, but the revised SBCC schedule and homepage target final adoption on Nov 20, 2026. May 3, 2027, is the proposed effective date, not final until a CR-103 is filed. The notice title names the ‘2024 Washington State Energy Code’.

How Washington adopts the IECC residential

• Agency rule
• The legislature sets the update schedule
• The legislature reviews the rules and can block them
• A recent law changed the process

The Council must review the residential energy code every three years and amends it by rule; decisions must be made before December 1 and may not take effect before the end of the next regular legislative session (RCW 19.27A.045). From Dec 5, 2024, the statute, as amended by Initiative 2066, barred provisions that prohibit, penalize or discourage gas heating; the Washington Supreme Court voided I-2066 in its entirety on Sep 17, 2026, although the online RCW still showed its wording on Oct 17, 2026. The 2024 WSEC is now moving through CR-102 and awaits final adoption.

Cycle. Triennial; 2021 WSEC effective Mar 15, 2024, 2024 WSEC targeted for May 3, 2027.

Laws, rulings, and other actions

1. Sep 17, 2026Court ruling
   Washington Supreme Court, Climate Solutions v. State, No. 104240-0

   Held I-2066 violates the single-subject requirement (art. II, sec. 19) and is void in its entirety, affirming the superior court on narrower grounds; Chief Justice Stephens wrote the majority and Justice Mungia dissented.

2. Aug 14, 2026Other action
   SBCC revises the 2024 code adoption schedule (latest revision dated Aug 14, 2026)

   The revised schedule targets final adoption of the 2024 IBC, IRC and IFC on Oct 16, 2026, and of the 2024 energy codes on Nov 20, 2026, with a May 3, 2027, effective date; in 2025 the Council had sought to keep a Nov 1, 2026, implementation date (secondary source).

3. May 9, 2025Court ruling
   King County Superior Court invalidates Initiative 2066

   Judge Sandra Widlan held I-2066 unconstitutional (ruling reported from the bench in March 2025; written order filed May 9, 2025), later affirmed by the Washington Supreme Court.

4. Apr 25, 2025Other action
   SBCC response to I-2066 petitions on the 2021 energy codes

   On Feb 6, 2025, the Council voted 10-2 against finding an emergency and opened a petition window for the 2021 WSEC; on Apr 25, 2025, after the King County ruling, it kept the petitions on file and ended the CR-101 process, with no amendment of the 2021 WSEC.

5. Feb 14, 2025Court ruling
   Thurston County Superior Court dismisses BIAW suit to force Council action on I-2066

   Judge John Skinder dismissed the Building Industry Association of Washington’s suit seeking to make the Council act faster to align the energy codes with I-2066 (news report).

6. Nov 5, 2024Ballot measure
   Initiative Measure No. 2066 (chapter 1, Laws of 2025), energy choice and access to gas

   Voters approved I-2066 (effective Dec 5, 2024), which barred the Council from adopting energy code provisions that prohibit, penalize or discourage gas use (amending RCW 19.27A.020, .025 and .045) and changed gas utility and local regulation rules; the Washington Supreme Court later voided it entirely.

7. Mar 18, 2024Legislation
   ESSB 62912024 regular session, chapter 170, Laws of 2024

   Restructures State Building Code Council procedure (amends RCW 19.27.031, .070, .074, 19.27A.025 and .045): one substantive update per three-year cycle, criteria and technical advisory groups for statewide amendments, and emergency amendments only on a two-thirds-approved Council finding.

   Enacted Mar 18, 2024, effective Jun 6, 2024

   lawfilesext.leg.wa.gov (opens in a new tab)
8. Mar 15, 2024Legislation
   SB 61202024 regular session, chapter 133, Laws of 2024

   Ties adoption of the Wildland Urban Interface Code to completion of statewide wildfire hazard and risk maps (RCW 19.27.560), so WAC 51-55 stays reserved with no state amendments; this is a separate code, not one of the six tracked slots.

   Enacted Mar 15, 2024, effective Mar 15, 2024

   lawfilesext.leg.wa.gov (opens in a new tab)
9. Mar 8, 2024Court ruling
   Thurston County Superior Court declines to delay the 2021 code update, including its heat pump energy code rules

   Judge Carol Murphy refused an industry request to put the rules on hold before they took effect on Mar 15, 2024, saying the court was weighing in on procedural aspects of adoption, not policy (news report; date taken from the article URL; the underlying challenge was reported as still pending).

10. Jan 16, 2024Other action
    SBCC amends the 2021 WSEC-R and WSEC-C to address EPCA preemption

    Permanent rules WSR 24-03-084 (chapter 51-11R WAC) and WSR 24-03-085 (chapter 51-11C WAC), filed Jan 16, 2024, and effective Mar 15, 2024, respond to a Ninth Circuit ruling expanding EPCA preemption.

11. Sep 15, 2023Other action
    SBCC delays implementation of all 2021 codes to Mar 15, 2024

    The Council voted to move implementation of the 2021 codes from Oct 29, 2023, to Mar 15, 2024 (as described in WSR 23-23-104); the final date is stated in WAC 51-50-008 and 51-51-008.

How it was checked

Verified

Two separate readings of the state’s own record agree, and the passage is on file word for word.

Read twice: a second, blind reading of the state’s record agreed with the first on Oct 18, 2026.

The state’s record was last read on Oct 18, 2026, from five source pages.

Evidence 6 sources

Sources for the record itself come first, the state’s own records ahead of others. A label marks a source about something else, such as an exception. A source marked secondary is not the state’s own record.

• “Effective Date of Rule: March 15, 2024.”

• “The 2021 edition of the Washington State Energy Code is hereby adopted.”

• “WSR 24-03-084, § 51-11R-10100, filed 1/16/24, effective 3/15/24”

• “STATE BUILDING CODE ADOPTION AND AMENDMENT OF THE 2021 EDITION OF THE INTERNATIONAL ENERGY CONSERVATION CODE, RESIDENTIAL”

• “2021 Code Editions and Amendments Effective March 15, 2024”

• About a related rule or action

Tracker cross-checks

Code adoption trackers are a cross-check. They are not Washington’s own record.

• DOE’s energycodes.govCross-checkAgrees with the record

  Residential: 2021 Washington State Energy Code with state amendments, effective 03/15/2024; DOE equivalence 2024 IECC; latest certification 2021 IECC; no next code listed

  energycodes.gov (opens in a new tab)Read Oct 17, 2026

Related pages

• See Washington’s IECC residential on the map
• IECC residential adoption in every state
• All six codes in Washington

Other codes in Washington

• NEC2023 NECVerified
• IBC2021 IBCVerified
• IRC2021 IRCVerified
• IFC2021 IFCVerified
• IECC commercial2021 IECCVerified