International Energy Conservation Code, residential
Illinois enforces the 2024 IECC residential
The 2024 International Energy Conservation Code (IECC) for residential buildings has been in force in Illinois since Nov 30, 2025. It applies statewide. Adopted by Capital Development Board. The legal citation is 71 Ill. Adm. Code 600.400; 20 ILCS 3125/15.
Record of adoption
Edition in force
2024 IECC
Illinois Energy Conservation Code (2024)
Verified
- In force since
- Legal citation
- 71 Ill. Adm. Code 600.400; 20 ILCS 3125/15
- Adopted by
- Capital Development Board
- Second reading
- Applies
- Statewide
- Also called
- ILECC, 2024 ILECC, 71 Ill. Adm. Code 600
Section 600.100 definitions still describe the 2021 IECC (amended Jan 1, 2025); the operative sections and appendix name the 2024 IECC.
Exceptions
- Chicago enforces its own Chicago Energy Transformation Code (based on the 2021 IECC, eff. Nov 1, 2022)
Coming next
- Edition not knownPartialNo date yetIn development20 ILCS 3125/55; P.A. 104-0315 (HB 3510)
CDB page lists 2026 Stretch Energy Code proposals. HB 3510 (P.A. 104-0315, eff. Jan 1, 2026) moved the stretch-code adoption deadlines. This is an optional overlay, not the next base edition. No next base-code edition (2027 IECC) adoption found.
How Illinois adopts the IECC residential
The Capital Development Board, in consultation with the Agency named in the Act, adopts the Illinois Energy Conservation Code by administrative rule (71 Ill. Adm. Code 600), incorporating a model IECC edition with Illinois amendments. Rules go through JCAR review, which can object or prohibit filing. The legislature set the Board as adopter and set deadlines for the optional Stretch Energy Code, most recently changed by P.A. 104-0315.
Cycle. Agency-initiated, roughly every three years following the IECC cycle (per a University of Illinois EnergySense page)
Laws, rulings, and other actions
- LegislationP.A. 104-0315 (HB 3510, 104th General Assembly)
Amends the Energy Efficient Building Act’s Illinois Stretch Energy Code provisions, changing adoption dates for stretch-code targets.
Enacted Aug 15, 2025, effective Jan 1, 2026
ilga.gov (opens in a new tab) - LegislationSB 2491 (104th General Assembly)
Would change stretch-code adoption deadlines in the Energy Efficient Building Act.
Pending; last action Jun 2, 2025, re-referred to Assignments (superseded in substance by HB 3510)
my.ilga.gov (opens in a new tab) - Other actionChicago Energy Transformation Code effective
Chicago’s energy code, based on the 2021 IECC, took effect for city permits.
- LegislationP.A. 102-444, 102-662, 102-813 (102nd General Assembly)
Listed in the source note of 20 ILCS 3125/15 as amending the Board’s energy-code adoption section.
Enacted, effective Aug 20, 2021, Sep 15, 2021, and May 13, 2022
ilga.gov (opens in a new tab) - UndatedLegislationHB 4994 (104th General Assembly)
Would let counties as well as municipalities adopt the Illinois Stretch Energy Code.
Pending; shown as Introduced
my.ilga.gov (opens in a new tab)
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 five 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.
“The 2024 IECC, including published errata but excluding published supplements (published May 2024)”
“(Source: Amended at 49 Ill. Reg. 15562, effective November 30, 2025)”
Section 600.400 Illinois Energy Conservation Code (residential)Illinois General Assembly, Joint Committee on Administrative Rulesilga.gov (opens in a new tab)Administrative codeRetrieved From Policy to Practice: Illinois Advances Energy Efficiency with New CodesMidwest Energy Efficiency Alliancemwalliance.org (opens in a new tab)News, secondaryRetrieved About a coming change
Illinois Energy CodesIllinois Capital Development Boardcdb.illinois.gov (opens in a new tab)Agency pageRetrieved Background
Section 600.100 DefinitionsIllinois General Assembly, Joint Committee on Administrative Rulesilga.gov (opens in a new tab)Administrative codeRetrieved
Tracker cross-checks
Code adoption trackers are a cross-check. They are not Illinois’s own record.
About a tracker cross-check
Illinois State Code StatusCross-checkUS Department of Energy, Building Energy Codes Programenergycodes.gov (opens in a new tab)Tracker, secondaryRetrieved
DOE’s energycodes.govCross-checkAgrees with the record
Residential: 2024 IECC; State Amendments: Yes; Effective Date: 11/30/2025; Mandatory Statewide
ICC’s code adoption mapCross-checkAgrees with the record
24 (2024 IECC adopted); chart as of 2026-04
Related pages
- See Illinois’s IECC residential on the map
- IECC residential adoption in every state
- All six codes in Illinois