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Illinois HVAC Legislation, Codes, and Guidelines

State-Level Building Codes and Legislation for HVAC in Illinois

In Illinois, the regulatory landscape for building codes, including HVAC requirements, has historically been decentralized, with local units of government (cities and counties) having the authority to adopt and enforce their own building codes. However, this is transitioning toward a more standardized statewide framework.

The most significant statewide mandate regarding HVAC systems is the Illinois Energy Conservation Code. Under the Energy Efficient Building Act (20 ILCS 3125), the state is required to adopt the latest published edition of the International Energy Conservation Code (IECC), typically with specific Illinois amendments. As of recent updates, Illinois has adopted the 2021 IECC. This code establishes mandatory minimum efficiency standards for HVAC equipment, ductwork, and system design for both new construction and major renovations in residential and commercial buildings.

Regarding general mechanical and structural codes (such as the International Mechanical Code or International Residential Code), Illinois has historically allowed local jurisdictions to choose their own standards. However, legislation (Public Act 103-0510) has been enacted to implement a statewide building code effective January 1, 2025. Under this new framework, local codes must regulate structural design in a manner at least as stringent as the International Building Code (IBC) for new commercial buildings or the International Residential Code (IRC) for residential buildings.

It is important to note that Illinois does not issue a statewide license for HVAC contractors or technicians. Licensing, permitting, and inspection requirements are handled entirely at the local municipal or county level. Professionals must verify the specific requirements of the jurisdiction where the work is being performed.

Primary State Agencies

Resources to Learn More

Select a County Below to Learn More About That Jurisdiction in Illinois

Permit rules operate within the above structure but can be nuanced at the county or municipal level. Select your local area below for specific ordinances, local codes, and direct links for your locality Building Department.