Chicago’s Green Roofs
Chicago has always been a city of progress and a leader of innovation, setting trends and raising the bar for others to follow and compete. Mayor Daley pledged to make the city of Chicago the greenest city in the nation; wondering what happened to the trees of his childhood, he had 400,000 trees planted almost immediately after taking office. Daley and the Environmental Department believe strongly that a “big city” and the environment can co-exist. To prove this theory to the people of Chicago as well as other cities across the nation, Daley transformed the rooftop of an iconic and very recognizable government building and set out to create the park Daniel Burnham fantasized about years ago.
Dr. Seuss’s Who character in Horton Hears a Who could be based off the type of creature that calls Chicago’s City Hall rooftop home. Because City Hall’s roof is usually off limits to humans, native organisms, insects, and land-nesting birds find sanctuary in its green roof. And although contact is prohibited, the roof is visually accessible from 33 taller buildings. The sight itself might seem to be another of Seuss’s creations as plants bloom across a sunburst pattern, complete with a Cockspur Hawthorn tree and a Prairie Crabapple (trees growing on a roof?). However, the purpose of this green roof was not to mimic a storybook but to test and research the benefits of green roofs, as well as promote educational outreach. Twenty thousand herbaceous plants were planted in lightweight soils of 4, 6 and 18 inches in depth on the half of the roof that City Hall’s owns. DuPage County, owner of the other half, remained black tar. Tests proved that the ambient air temperature on the green roof was 78 degrees cooler than the air temperature measured on the black tar membrane, which proves that green roofs are needed to combat the urban heat island effect. It also resulted in a savings of $5,000 a year on utility bills for City Hall and that the green roof could retain 75% of a 1-inch rainfall before storm water runoff into the sewers. This not only helps plants cool the air through evapotranspiration, but also contributes less waste to cities already bombarded sewer system. The success of City Hall’s green roof project fueled Mayor Daley’s ambitions to create something that would not only complement ideas of the past but also exude those of the future.
If you have ever been to Millennium Park, made faces in the Bean, or allowed the faces of the Crown Fountain to spit water at you, then you know you’ve visited a place of art. And if you’ve ever laid a blanket in the grass under the Pritzker Pavilion and listened to the orchestra play or strolled through the Laurie Botanical Garden and listened to the birds sing, you know that Millennium Park is a place of music. But, did you know that Millennium Park is also the largest intensive green roof project in the world? Just strolling around you’ll find everything from pear trees to maple trees to shrubs and perennials. It took city agencies, a private donor group, artists, landscapers, architects, engineers, construction managers and contractors six years to dream up and create this urban oasis. Work began in 1998 and two reinforced concrete cast-in place garages stand as the base creating a deck. The deck was then waterproofed with a hot applied rubberized membrane system and Styrofoam fill created landforms. Trees and plants with longer root systems were planted on these landforms and then grass and native shrubbery completed the design. With Chicago’s erratic weather patterns this green roof absorbs and polishes storm water, purifies the air and helps to reduce the urban heat island effect. Millennium Park, with its almost twenty-five acres of recreation and beauty, serves not only to please the citizens of Chicago but also to please the environment.
Chicago has indeed earned the title, “Greenest City in the Nation,” with over seven million square feet of green roofs perched upon public and private property. Green roofs are springing up everywhere; the Center for Green Technology, the Mac store on Michigan Ave, Target, McDonald’s on Ontario St., PepsiCo, Aldi Supermarket, and Wal-mart, to name a few. Willis Tower is even participating with a partial green roof located on the 90th floor and tied down with steel ropes to protect against the wind. Every patch helps in creating an environment where a big city and mother nature can co-exist.
Thanks to these awesome sources for helpful info in putting this article together:
“Greenroofs.com Projects – Chicago City Hall.” Greenroofs.com: The Resource Portal for Green Roofs. N.p., n.d. Web. 14 July 2010.
“Willis Tower | Alter NOW.” The Alter Group – Home. N.p., 17 May 2010. Web. 21 July 2010. .
Yocca, David. “Chicago City Hall Green Roof.” American Society of Landscape Architects – Home . N.p., n.d. Web. 13 July 2010. corner, completing the historic park’s northwest, and consequently stabilizing.
“Green Rooftops for Sustainable Communities.” Green Roofs for Healthy Cities. N.p., n.d. Web. 16 July 2010.