The Department of Buildings enforces the Chicago Building Code, which includes the Chicago Heat Ordinance. The Heat Ordinance mandates that during cold weather months landlords supply heat to rental units or to any unit where owners do not have individual control of the heat.

From September 15 through June 1, the temperature inside a rental residence is required to be at least 68 degrees from 8:30 am to 10:30 pm, and at least 66 degrees from 10:30 pm to 8:30 am.

More information can be found here.