For the third consecutive year, Illinois was ranked first among the states in a survey of energy-conserving buildings. According to the U.S. Green Building Council (USGBC), Illinois had 161 new and renovated projects in 2015 that earned LEED (for Leadership in Energy and Environmental Design) certification. Those projects included the high-profile renovations of the Virgin Hotel and the Chase Tower, both in the Chicago Loop.

According to reports from the Chicago Tribune, the survey ranks states on a per-capita basis. Trailing Illinois were Maryland, Massachusetts, Washington and Colorado. California had the most square feet of LEED-certified projects — more than 87 million square feet compared with Illinois' nearly 44 million square feet — but it ranked seventh on a per-capita basis.

Illinois draws a lot of attention from the USGBC because of the many corporations that have adopted green building and cleaning practices. Also, the state and Chicago governments often require them.