Energy.gov

''Much of the information presented in this summary is drawn from the U.S. Department of Energy’s (DOE) Building Energy Codes Program and the Building Codes Assistance Project (BCAP). For more detailed information about building energy codes, visit the DOE and BCAP websites.''

Prior to 2004 the primary energy conservation law in Illinois was the Illinois Public Utilities Act (revised in 1986.) This law required Illinois investor-owned electric utilities to use least-cost energy planning, which required the use of economical energy conservation when new resources for electricity were required. This requirement was implemented by utilities and monitored by the Illinois Commerce Commission through the least-cost energy planning process.

Public Act 093-0936 (Illinois Energy Conservation Code for Commercial Buildings) was signed into law in August, 2004. The Illinois Energy Conservation Code for Commercial Buildings became effective April 8, 2006. This law requires all commercial construction for which a building permit application is received by a municipality or county to follow a comprehensive statewide energy conservation code. The Capital Development Board has the authority to create administrative rules, and its most recent rule amendments mandated that the code for commercial buildings follow 2009 International Energy Conservation Code (IECC) (as of August 2009). Municipalities and counties are required to enforce 2009 IECC.

On May 31, 2009, the Illinois General Assembly approved the Energy Efficient Building Act (HB 3987), which was signed into law on August 28, 2009. The legislation directed the Illinois Capital Development Board (CDB) to adopt the Illinois Energy Conservation Code, which became effective January 29, 2010. The new statewide code (71 IAC 600) incorporates the 2009 IECC for residential buildings and privately funded commercial buildings and ASHRAE 90.1-2007 for publicly funded commercial buildings (previously, there was not a mandatory residential statewide energy code based on the IECC). An automatic update provision directs the CDB to adopt each subsequent version of the IECC within nine months of its publication, with an effective date three months afterwards.

The legislation also removed local home rule jurisdiction over residential energy standards. Local governments are allowed to adopt more stringent energy codes for commercial buildings (but not less stringent). These jurisdictions also may not adopt residential codes more or less stringent than the state code (however, exemptions to go above the state residential code are made for municipalities that adopted at least the 2006 IECC before May 2009 or have more than 1,000,000 residents).