Illinois mechanical, plumbing, fuel gas & energy codes
Illinois has no statewide mechanical or fuel gas code. Cities and counties adopt their own and must report them to the Capital Development Board (CDB). The statewide rules that do apply are the Illinois Plumbing Code (IDPH) and the Illinois Energy Conservation Code (CDB).
Quick answer: Illinois has no statewide mechanical or fuel gas code, so check the city or county. Plumbing follows the state-written Illinois Plumbing Code (77 Ill. Adm. Code 890), and Chicago has its own codes. A2L status: Allowed by state law; local codes can differ
Adopted codes
Mechanical
No statewide code
Local adoption
- Adopted as
- No statewide mechanical code
- Effective
- n/a
- Source
- Illinois CDB – Building Codes and Regulations
- Last checked
- 2026-10-29 verified
- Notes
- Local governments adopt their own mechanical codes and must report the title and edition to CDB at least 30 days before the effective date (20 ILCS 3105/10.18).
Plumbing
77 IAC 890
State-written code
- Adopted as
- Illinois Plumbing Code, 77 Ill. Adm. Code 890 (IDPH)
- Effective
- 2014-04-24
- Source
- Illinois Administrative Code – Part 890 (JCAR)
- Last checked
- 2026-10-29 verified
- Notes
- State-written code. Last amended effective Apr 24, 2014 (38 Ill. Reg. 9940). Applies statewide per the CDB summary. IDPH has a pending proposed amendment covering Legionella, lead and harvested-water systems.
Fuel Gas
No statewide code
Local adoption
- Adopted as
- No statewide fuel gas code
- Effective
- n/a
- Source
- Illinois CDB – Building Codes and Regulations
- Last checked
- 2026-10-29 verified
- Notes
- No statewide fuel gas code. Use the local code.
Energy
Residential: 2024 IECC; Commercial: 2024 IECC & ASHRAE 90.1-2022
IECC / ASHRAE 90.1
- Adopted as
- State energy code (per U.S. DOE BECP)
- Effective
- Res 2025-11-30; Com 2025-11-30
- Source
- U.S. DOE Building Energy Codes Program – Illinois
- Last checked
- 2026-10-29 verified
- Notes
- DOE lists the effective date as 11/30/2025. Illinois also has a Stretch Energy Code for CDB-funded buildings.
A2L refrigerants in Illinois
415 ILCS 5/9.19 (P.A. 103-230, eff. June 30, 2023) allows EPA-approved refrigerants statewide if the equipment is listed and installed under the related safety standards and use conditions. The same section keeps local governments' power to authorize or prohibit alternative refrigerants, so check the local mechanical code.
Source: https://ilga.gov/documents/legislation/ilcs/documents/041500050K9.19.htm · Last checked 2026-10-29 verified
Local amendments & things to watch
- Chicago: the 2026 Chicago Mechanical Code (Title 14M), Fuel Gas Code (14G) and Energy Transformation Code (14N) have been optional since Oct 1, 2026. They become mandatory for permit applications started on or after Dec 1, 2026. verified source
- Chicago plumbing: the 2001 Chicago Plumbing Code with 2021 amendments has been mandatory for permit applications started on or after Mar 1, 2022. verified source
- Since Jan 1, 2025, local codes must regulate structural design at least as strictly as the IBC (new) or IEBC (existing) (Public Act 103-0510). verified source