Chicago City Hall Green Roof. Green Roofs are something Chicago is known for, with one of the most famous green roofs on the Chicago City Hall. Green Roofs are also economically beneficial alongside environmentally. A Green Roof can insulate a building, reducing energy costs, cool the building during the summer, and according to a study by University of Toronto professor have beneficial effects during the winter, which is expanded upon here, "https://www.treehugger.com/sustainable-product-design/first-ever-analysis-of-green-roofsatm-ability-to-keep-buildings-warm-in-winter.html".