International Energy Conservation Code, commercial
Washington enforces the 2021 IECC commercial
The 2021 International Energy Conservation Code (IECC) for commercial buildings has been in force in Washington since Mar 15, 2024. It applies statewide. Adopted by Washington State Building Code Council. The legal citation is WAC 51-11C-10100; chapter 19.27A RCW (RCW 19.27A.025).
Record of adoption
Edition in force
2021 IECC
Washington State Energy Code, Commercial Provisions, 2021 edition (chapter 51-11C WAC)
Verified
- In force since
- Legal citation
- WAC 51-11C-10100; chapter 19.27A RCW (RCW 19.27A.025)
- Adopted by
- Washington State Building Code Council
- Second reading
- Applies
- Statewide
- State amendments
- Major
- Also called
- WSEC-C, WAC 51-11C, 2021 WSEC commercial
The WAC chapter title names the 2021 IECC. The state code is the Washington State Energy Code (WSEC-C) with Washington amendments, including EPCA-related changes in WSR 24-03-085 that took effect with the code. The state amendments are rated substantial because Washington rewrites the IECC into its own WSEC chapter. DOE frames the commercial code through ASHRAE 90.1 rather than the IECC.
Coming next
- 2024 IECCPartialPlanned for May 3, 2027ProposedWAC 51-11C (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. The May 3, 2027, effective date comes from the SBCC schedule and homepage (the notice itself gave none) and is not final until a CR-103 is filed.
How Washington adopts the IECC commercial
Nonresidential energy code amendments are made by Council rule after consulting a technical advisory group; decisions must be made before December 15 and may not take effect before the end of the next regular legislative session (RCW 19.27A.025). Any provision adopted by less than two-thirds of the voting members is ‘disputed’ and must be approved by the Legislature before it takes effect, and substantial amendments are limited to once every three years. The gas language added by Initiative 2066 also reached RCW 19.27A.025 until the Supreme Court voided I-2066 on Sep 17, 2026.
Cycle. Triennial; 2021 WSEC effective Mar 15, 2024, 2024 WSEC targeted for May 3, 2027.
Laws, rulings, and other actions
- Court rulingWashington 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.
- Other actionSBCC 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).
- Court rulingKing 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.
- Other actionSBCC 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.
- Court rulingThurston 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).
- Ballot measureInitiative 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.
- LegislationESSB 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) - LegislationSB 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) - Court rulingThurston 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).
- Other actionSBCC 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.
- Other actionSBCC 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 .
The state’s record was last read on , from four source pages.
Evidence 4 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.
“STATE BUILDING CODE ADOPTION AND AMENDMENT OF THE 2021 EDITION OF THE INTERNATIONAL ENERGY CONSERVATION CODE, COMMERCIAL”
Chapter 51-11C WACWashington State Legislature (Office of the Code Reviser)app.leg.wa.gov (opens in a new tab)Administrative codeRetrieved “WSR 24-03-085, § 51-11C-10100, filed 1/16/24, effective 3/15/24”
WAC 51-11C-10100 Section C101 Scope and general requirementsWashington State Legislature (Office of the Code Reviser)app.leg.wa.gov (opens in a new tab)Administrative codeRetrieved “2021 Code Editions and Amendments Effective March 15, 2024”
State Building Code Council home page (announcements)Washington State Building Code Councilsbcc.wa.gov (opens in a new tab)Agency pageRetrieved About the note
“Group 3 - Addressing EPCA Concerns in the 2021 Washington State Energy Code - Commercial”
2021 Code Adoption CycleWashington State Building Code Councilsbcc.wa.gov (opens in a new tab)Agency pageRetrieved
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
Commercial: 2021 Washington State Energy Code with state amendments, effective 03/15/2024; DOE equivalence ASHRAE 90.1-2022; latest certification ASHRAE 90.1-2019; no next code listed
Related pages
- See Washington’s IECC commercial on the map
- IECC commercial adoption in every state
- All six codes in Washington