Ill. Admin. Code tit. 71, § 600.APPENDIX A – Illinois Energy Conservation Code Amendments to the 2024 International Energy Conservation Code

1. Compliance forms published in the ASHRAE 90.1 User's Manual; or
1. 2. Compliance Certificates generated by the U.S. Department of Energy's COMcheck^TM Code compliance tool; or
2. 3. Other comparable compliance materials that meet or exceed, as determined by the AHJ, the compliance forms published in the ASHRAE 90.1 User's Manual or the U.S. Department of Energy's COMcheck^TM code compliance tool; or
3. 4. The seal of the architect/engineer as required by Section 14 of the Illinois Architectural Practice Act [225 ILCS 305], Section 12 of the Structural Engineering Licensing Act [225 ILCS 340] and Section 14 of the Illinois Professional Engineering Practice Act [225 ILCS 325].
4. 5. Compliance materials required by C407 Simulated Building Performance or C410 Passive Building Compliance Option when those respective compliance paths are utilized.
  C104.1.1 Above code programs. No unit of local government, including any home rule unit, may apply energy efficient building standards to privately funded commercial facilities in a manner that is less stringent than this Code as described in 71 Ill. Adm. Code 600.Subpart C. However, nothing in the EEB Act or Subpart C prevents a unit of local government from adopting an energy efficiency code or standards that are more stringent than this Code. The requirements identified in Table C407.2(1) shall be met.
  C105.2.2 Electrification system. The construction documents shall provide details for additional electric infrastructure, including branch circuits, raceway capacity, pre-wiring, panel capacity, and electrical service capacity, as well as interior and exterior spaces designated for future electric equipment, in compliance with the provisions of this Code.
  SECTION C109
  MEANS OF APPEALS
  C109.1 General. In order to hear and decide appeals of orders, decisions or determinations made by the code official relative to the application and interpretation of this Code, there may be created a board of appeals. The code official shall be an ex officio member of the board of appeals but shall not have a vote on any matter before the board. The board of appeals shall be appointed by the governing body and shall hold office at its pleasure. The board shall adopt rules of procedure for conducting its business and shall render all decisions and findings in writing to the appellant with a duplicate copy to the code official.
  C109.3 Qualifications. The board of appeals shall consist of members who are qualified by experience and training on matters pertaining to the provisions of this Code.
  CHAPTER 2 [CE]
  DEFINITIONS
  SECTION C202
  GENERAL DEFINITIONS
  AUTHORITY HAVING JURISDICTION (AHJ). The organization, officer or individual responsible for approving equipment, materials, an installation or procedure.
  BOARD. The Illinois Capital Development Board.
  COMMERCIAL COOKING APPLIANCES. Commercial cooking appliances used in a commercial food service establishment for heating or cooking food and which produce grease vapors, steam, fumes, smoke or odors that are required to be removed through a local exhaust ventilation system. Such appliances include deep fat fryers, upright broilers, griddles, broilers, steam-jacketed kettles, hot-top ranges, under-fired broilers (charbroilers), ovens, barbecues, rotisseries and similar appliances.
  COMMERCIAL CLOTHES DRYING APPLIANCES. Clothes drying appliances meeting the definition of clothes dryer (Type 2) in the 2021 International Fuel Gas Code published by the International Code Council, or tested in accordance with Underwriters Laboratories (UL) 2158-2021 Standard for Safety for Electric Clothes Dryers or UL 1240-2021 Standard for Electric Commercial Clothes-Drying Equipment and installed in a commercial laundry establishment.
  COUNCIL. The Illinois Energy Conservation Advisory Council whose purpose is to recommend modifications to the Illinois Energy Conservation Code.
  EEB ACT. The Energy Efficient Building Act [20 ILCS 3125].
  RESIDENTIAL BUILDING. A detached one-family or two-family dwelling or any building that is three stories or less in height above grade that contains multiple dwelling units, in which the occupants reside on a primarily permanent basis, such as a townhouse, a row house, an apartment house, a convent, a monastery, a rectory, a fraternity or sorority house, a dormitory, and a rooming house; provided, however, that when applied to a building located within the boundaries of a municipality having a population of 1,000,000 or more, the term "RESIDENTIAL BUILDING" means a building containing one or more dwelling units, not exceeding four stories above grade, where occupants are primarily permanent. (See 20 ILCS 3125/10.)
  CHAPTER 4 [CE]
  COMMERCIAL ENERGY EFFICIENCY
  SECTION C401-GENERAL
  C401.2.3 Passive building compliance option. The passive building compliance option requires compliance with Section C410.
  SECTION C402
  BUILDING THERMAL ENVELOPE REQUIREMENTS
  C402.6.1.2 Air barrier construction. The continuous air barrier shall be constructed to comply with the following:
5. 1. The air barrier shall be continuous for all assemblies that are the thermal envelope of the building and across the joints and assemblies.
6. 2. Air barrier joints and seams shall be sealed, including sealing transitions at joints between dissimilar materials. The joints and seals shall be securely installed in or on the joint for its entire length so as not to dislodge, loosen or otherwise impair its ability to resist positive and negative pressure from wind, stack effect and mechanical ventilation.
7. 3. Penetrations of the air barrier shall be caulked, gasketed or otherwise sealed in a manner compatible with the construction materials and location. Sealings shall allow for expansion, contraction and mechanical vibration. Paths for air leakage from the building to the space between the roof deck and roof covering used as an air barrier shall be caulked, gasketed or otherwise covered with a moisture vapor-permeable material. Joints and seams associated with penetrations shall be sealed in the same manner or taped. Sealing materials shall be securely installed around the penetration so as not to dislodge, loosen or otherwise impair the penetrations' ability to resist positive and negative pressure from wind, stack effect and mechanical ventilation. Sealing of concealed fire sprinklers, where required, shall be in a manner that is recommended by the manufacturer. Caulking or other adhesive sealants shall not be used to fill voids between fire sprinkler cover plates and walls or ceilings.
8. 4. Recessed lighting fixtures shall comply with Section C402.6.1.2.1. Where similar objects are installed that penetrate the air barrier, provisions shall be made to maintain the integrity of the air barrier.
9. 5. Electrical and communication boxes shall comply with Section C402.6.1.2.2.
  1. 1. Indoor grow buildings with less than 40kW of connected load for horticultural lighting shall have a PPE of at least 1.7 μmol/J for integrated, nonserviceable luminaires, or a PPE of at least 1.7 μmol/J for lamps in luminaires with removable or serviceable lamps.
  2. 2. Cannabis facilities subject to 410 ILCS 705/10-45, the Cannabis Regulation and Tax Act.
    SECTION C406
    ADDITIONAL EFFICIENCY, RENEWABLE AND LOAD MANAGEMENT REQUIREMENTS
    C406.1.1 Additional energy efficiency credit requirements. Buildings shall comply with measures from Section C406.2 to achieve not less than the number of required efficiency credits from Table C406.1.1(1) based on building occupancy group and climate zone. Where a project contains multiple occupancies, the total required energy credits from each building occupancy shall be weighted by the gross conditioned floor area to determine the weighted-average project energy credits required. Accessory occupancies shall be included with the primary occupancy group for the purposes of Section C406.
    SECTION C410-PASSIVE BUILDING COMPLIANCE OPTION
    C410.1 Phius standard compliance. Compliance based on the Phius CORE 2024 of Phius ZERO 2024 Passive Building Standard (2024 Edition), published by Phius (Passive House Institute US, Inc.), 1807 W Sunnyside Ave., Suite 1G, Chicago, Illinois 60640, must include performance calculations by Phius-approved software or the use of the Phius Prescriptive Path.
    C410.1.1 Phius documentation. Prior to the issuance of a building permit, a Phius Design Certification letter must be provided to the code official.
    C410.1.2 Project certificate. Prior to the issuance of a certificate of occupancy, a Phius 2024 (or later) final certificate must be provided to the code official.
    C410.2 PHI standard compliance. Compliance based on Passive House Planning Package (PHPP), Version 10 (2021 Edition), published by the Passive House Institute (PHI), Rheinstrasse 44/46, 64283 Darmstadt, Germany, shall be shown via Low Energy Building, Classic, Plus, or Premium certification by PHI.
    C410.2.1 PHI documentation. Prior to the issuance of a building permit, a signed Design Stage Conditional Assurance Letter from a PHI-accredited Passive House Certifier confirming intent to certify the building must be provided to the code official.
    C410.2.2 Project certificate. Prior to the issuance of a certificate of occupancy, a copy of either a Certifiers Assurance Letter by an approved PHI-accredited Certifier or a final PHI Certificate to document compliance with Passive House Standards must be provided to the code official.
    CHAPTER 1 [RE]
    SCOPE AND ADMINISTRATION
    SECTION R101
    SCOPE AND GENERAL REQUIREMENTS
    R101.1 Title. This Code shall be known as the 2024 Illinois Energy Conservation Code or Code and shall mean:
    With respect to the residential buildings covered by 71 Ill. Adm. Code 600.Subpart D:
    This Part, all additional requirements incorporated within Subpart D (including the 2024 International Energy Conservation Code, including all published errata but excluding published supplements) and any statutorily authorized adaptations to the incorporated standards adopted by CDB are effective November 30, 2025.
    R101.1.1 Adoption. The Board shall adopt amendments to this Code within 12 months after publication of the 2024 International Energy Conservation Code. Any such update in this Code shall take effect within 6 months after it is adopted by the Board and shall apply to any new building or structure in this State for which a building permit application is received by a municipality or county, except as otherwise provided by the EEB Act.
    R101.1.2 Adaptation. The Board may appropriately adapt the International Energy Conservation Code to apply to the particular economy, population distribution, geography and climate of the State and construction within the State, consistent with the public policy objectives of the EEB Act.
    R101.4 Compliance. Residential buildings shall meet the provisions of the Illinois Energy Conservation Code covered by 71 Ill. Adm. Code 600.Subpart D. The local authority having jurisdiction (AHJ) shall establish its own procedures for enforcement of the Illinois Energy Conservation Code. Minimum compliance shall be demonstrated by submission of:
  SECTION C405
  ELECTRICAL POWER AND LIGHTING SYSTEMS
  C405.4 Horticultural Lighting. Permanently installed luminaires shall have a photosynthetic photon efficacy of not less than 1.7 μmoles per joule (μmol/J) for horticultural lighting in greenhouses and not less than 1.9 μmol/J for all other horticultural lighting. Luminaires for horticultural lighting in greenhouses shall be controlled by a device that automatically turns off the luminaire when sufficient daylight is available. Luminaires for horticultural lighting shall be controlled by a device that automatically turns off the luminaire at specific programmed times.
  Exception: The following buildings are exempt:
10. 1. Compliance Certificates generated by the U.S. Department of Energy's REScheck^TM Code compliance tool; or
11. 2. Other comparable compliance materials that meet or exceed, as determined by the AHJ, U.S. Department of Energy's REScheck^TM Code compliance tool; or
12. 3. The seal of the architect/engineer as required by Section 14 of the Illinois Architectural Practice Act [225 ILCS 305], Section 12 of the Structural Engineering Licensing Act [225 ILCS 340] and Section 14 of the Illinois Professional Engineering Practice Act [225 ILCS 325].
  SECTION R104
  ALTERNATIVE MATERIALS, DESIGN AND METHODS
  OF CONSTRUCTION AND EQUIPMENT
  R104.1.1 Above code programs. No unit of local government, including any home rule unit, may regulate energy efficient building standards for residential buildings in a manner that is either less or more stringent than the standards established pursuant to this Code. Buildings shall be considered to be in compliance with this code where such buildings also meet the requirements identified in Table R405.2 and the proposed total building thermal envelope conductance (TC) shall be less than or equal to the total building thermal envelope TC using the prescriptive U-factors and F-factors from Table R402.1.2 multiplied by 1.15 in Climate Zones 4 and 5 (see Table C301.1), in accordance with Equation 1-1.
  Equation 1-1: For Climate Zones 3-8: TC_{Proposed Design}< 1.15 x TC_{Prescriptive reference design}
  However, the following entities may regulate energy efficient building standards for residential buildings in a manner that is more stringent than the provisions contained in this Code in accordance with 20 ILCS 3125/45:
13. 1. A unit of local government, including a home rule unit, that has, on or before May 15, 2009, adopted or incorporated by reference energy efficient building standards for residential buildings that are equivalent to or more stringent than the 2006 International Energy Conservation Code.
14. 2. A unit of local government, including a home rule unit, that has, on or before May 15, 2009, provided to the Capital Development Board, as required by Section 10.18 of the Capital Development Board Act, an identification of an energy efficient building code or amendment that is equivalent to or more stringent than the 2006 International Energy Conservation Code.
3. A municipality with a population of 1,000,000 or more.

4. A municipality that has adopted the Illinois Stretch Energy Code.

15. Greater than or equal to 120 Annual Fuel Utilization Efficiency (AFUE) gas heat pump space heating system (Option 1). The gas heat pump space heating system shall not be configured to provide cooling.
16. Greater than or equal to 140 AFUE gas heat pump space heating system (Option 2). The gas heat pump space heating system shall not be configured to provide cooling.
Remove section R408.2.9 Opaque walls.
SECTION R409
PASSIVE BUILDING COMPLIANCE OPTION
R409.1 Phius standard compliance. Compliance based on the Phius CORE 2024 of Phius ZERO 2024 (or later) Standard will include performance calculations by Phius-approved software or the use of the Phius Prescriptive Path.
R409.1.1 Phius documentation. Prior to the issuance of a building permit, a Phius Design Certification letter must be provided to the code official.
R409.1.2 Project certificate. Prior to the issuance of a certificate of occupancy, a Phius 2024 (or later) Final certificate must be provided to the code official.
R409.2 PHI standard compliance. Compliance based on Passive House Planning Package (PHPP), Version 10 (2021 Edition), publilshed by the Passive House Institute (PHI), Reinstrasse 44/46, 64282 Darmstadt, Germany, shall be shown via Low Energy Building, Classic, Plus, or Premium certification by PHI.
R409.2.1 PHI documentation. Prior to the issuance of a building permit, a signed Design Stage Conditional Assurance Letter from a PHI-accredited Passive House Certifier confirming intent to certify the building must be provided to the code official.
R409.2.2 Project certificate. Prior to the issuance of a certificate of occupancy, a copy of either a Certifiers Assurance Letter by an approved PHI-accredited Certifier or a final PHI Certificate to document compliance with Passive House Standards must be provided to the code official.
SECTION R503
ALTERATIONS
R503.1.1.2 Roof replacement. Insulation shall comply with Section R402.1. Alternatively, where limiting conditions prevent compliance with Section R402.1, an approved design that minimizes deviation from Section R402.1 shall be provided for the following alterations:

SECTION R109

MEANS OF APPEALS

R109.1 General. In order to hear and decide appeals of orders, decisions or determinations made by the code official relative to the application and interpretation of this Code, there may be created a board of appeals within each jurisdiction. The code official shall be an ex officio member of the board of appeals but shall not have a vote on any matter before the board. The board of appeals shall be appointed by the governing body and shall hold office at its pleasure. The board shall adopt rules of procedure for conducting its business and shall render all decisions and findings in writing to the appellant with a duplicate copy to the code official.

R109.3 Qualifications. The board of appeals shall consist of members who are qualified by experience and training on matters pertaining to the provisions of this Code.

CHAPTER 2 [RE]

DEFINITIONS

SECTION R202

GENERAL DEFINITIONS

AUTHORITY HAVING JURISDICTION (AHJ). The organization, officer or individual responsible for approving equipment, materials, an installation or procedure.

BOARD. The Illinois Capital Development Board.

COUNCIL. The Illinois Energy Conservation Advisory Council whose purpose is to recommend modifications to the Illinois Energy Conservation Code.

EEB ACT. The Energy Efficient Building Act [20 ILCS 3125].

LOCAL EXHAUST. An exhaust system that uses one or more fans to exhaust air from a specific room or rooms within a dwelling.

RESIDENTIAL BUILDING. A detached one-family or two-family dwelling or any building that is three stories or less in height above grade that contains multiple dwelling units, in which the occupants reside on a primarily permanent basis, such as a townhouse, a row house, an apartment house, a convent, a monastery, a rectory, a fraternity or sorority house, a dormitory and a rooming house; provided, however, that when applied to a building located within the boundaries of a municipality having a population of 1,000,000 or more, the term "residential building" means a building containing one or more dwelling units, not exceeding four stories above grade, where occupants are primarily permanent.

CHAPTER 4 [RE]

RESIDENTIAL ENERGY EFFICIENCY

SECTION R401

GENERAL

Replace section R401.2.4 with the following:

R401.2.4 Passive building compliance option. The Passive building compliance option requires compliance with Section R409.

SECTION R402

BUILDING THERMAL ENVELOPE

R402.2.1 Roof/ceilings with attics. Where Section R402.1.3 requires R-49 insulation in the ceiling or attic, installing R-38 over 100 percent of the ceiling or attic area requiring insulation shall satisfy the requirement for R-49 insulation wherever the full height of uncompressed R-38 insulation extends over the wall top plate at the eaves. This reduction shall not apply to the insulation and fenestration criteria in Section R402.1.2 and the component performance alternative in Section R402.1.5.

R402.2.2 Roof/ceilings without attics. When Section R402.1.3 requires insulation R-values greater than R-30 in the interstitial space above a ceiling and below the structural roof deck, and the design of the roof/ceiling assembly does not allow sufficient space for the required insulation, the minimum required insulation R-value for those roof/ceiling assemblies shall be R-30. Insulation shall extend over the top of the wall plate to the outer edge of the plate and shall not be compressed. This reduction of insulation from the requirements of Section R402.1.3 shall be limited to 500 square feet (46 m²) or 20 percent of the total insulated ceiling area, whichever is less. This reduction shall not apply to the component performance alternative in Section R402.1.5.

R402.2.9.1 Basement wall insulation installation. Where basement walls are insulated, the insulation shall be installed from the top of the basement wall down to 10 feet (3048 mm) below grade or to within 6 inches (152 mm) of the basement floor, whichever is less.

SECTION R403

SYSTEMS

R403.3 Duct systems. Duct systems shall be insulated, sealed, tested and installed in accordance with Sections R403.3.1 through R403.3.9. Where required by the code official, duct testing shall be conducted by an approved third party. A written report of the results of the test shall be signed by the party conducting the test and provided to the code official.

SECTION R408

ADDITIONAL EFFICIENCY PACKAGE OPTIONS

Revise the following rows in Table R408.2:

Measure Number	Measure Description	Climate Zone 4 Except Marine	Climate Zone 5
R408.2.2 (15)	High-performance gas heat pump space heating system. (Option 1)	9	11
R408.2.2 (16)	High-performance gas heat pump space heating system. (Option 2)	11	14
R408.2.2 (10)^b	High Performance Electric Heat pump with electric resistance backup (Option 1)	12	NA
R408.2.2 (14)^b	High Performance Electric Heat pump with electric resistance backup (Option 2)	12	12

Add subparagraphs 15 and 16 to R408.2.2:

The following Code sections shall be referenced in place of the corresponding 2024 IECC sections.

CHAPTER 1 [CE]

SCOPE AND ADMINISTRATION

SECTION C101

SCOPE AND GENERAL REQUIREMENTS

C101.1 Title. This Code shall be known as the 2024 Illinois Energy Conservation Code or Code and shall mean:

With respect to the privately funded commercial facilities covered by 71 Ill. Adm. Code 600.Subpart C:

This Part, all additional requirements incorporated within Subpart C (including the 2024 International Energy Conservation Code, including all published errata and excluding published supplements that encompass ASHRAE 90.1-2022), and any statutorily authorized adaptations to the incorporated standards adopted by CDB, are effective November 30, 2025.

C101.1.1 Adoption. The Board shall adopt amendments to this Code within 12 months after publication of the 2024 International Energy Conservation Code. Any such update in this Code shall take effect within 6 months after it is adopted by the Board and shall apply to any new building or structure in this State for which a building permit application is received by a municipality or county, except as otherwise provided by the EEB Act.

C101.1.2 Adaptation. The Board may appropriately adapt the International Energy Conservation Code to apply to the particular economy, population distribution, geography and climate of the State and construction within the State, consistent with the public policy objectives of the EEB Act.

C101.4 Compliance. Commercial buildings shall meet the provisions of the Illinois Energy Conservation Code covered by 71 Ill. Adm. Code 600.Subpart C. The local authority having jurisdiction (AHJ) shall establish its own procedures for enforcement of the Illinois Energy Conservation Code. Minimum compliance shall be demonstrated by submission of:

(Source: Amended at 49 Ill. Reg. 15562, effective November 30, 2025)