As of the writing of this report, the state of Illinois does not have a statewide building energy efficiency code for residential buildings, although a number of jurisdictions in Illinois have adopted the 2000 International Energy Conservation Code (IECC) or the 2003 IECC.

The U.S. Department of Energy requested Pacific Northwest National Laboratory estimate the energy savings, economic impacts, and pollution reduction from adopting the 2006 IECC. This report addresses the impacts for low-rise residential buildings only.