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Green Acres in the Sky

Chicago's City Hall is the poster child for green roofs, but the city boasts many others

Chicago's City Hall occupies the western half of an 11-story, classical revival-style building that takes up an entire city block. What you don't notice from the street is the building's 20,300-square-foot green roof, which Greenroofs.com publisher and design consultant Linda Velazquez calls "the poster child of green roofs." It's impossible to see the honeybees flying from the roof's purple coneflowers to prairie clovers, the Monarch butterflies fluttering past little bluestems and the native grasses and prairie plants wafting on the building's rooftop. The plants have helped lower the roof's summer temperature from highs of nearly 170 degrees when the roof was covered in black tar to roughly 90 degrees, according to Sadhu Johnston, commissioner of the Chicago Department of Environment.

Since being installed as a $2.5 million experiment to examine the roof's ability to combat the "urban heat island effect," which traps heat and air pollution in the congested Loop, Johnston and his staff realized that if "we could utilize these strategies to cool the city by just one degree, we would save $150 million in air conditioning costs per year."

Ever since that revelation, Mayor Richard M. Daley, Johnston and his staff have embarked on a crusade to publicize green roofs' abilities to beat the urban heat island effect, as well as their ability to absorb storm water and extend a roof's life up to 50 years. With more than 3 million square feet among roughly 300 green roofs either built or in development, the campaign has made Chicago the North American leader of the green roof movement, says Jennifer Sprout, director of Green Roofs for Healthy Cities.

"[Chicago] is a great blueprint for what other municipalities can do," Sprout says, noting that green roofs cover nearly every type of building in Chicago--from Target stores and the Schwab Rehabilitation Hospital to the McCormick Place Convention Center West Building and Northwestern's new Prentice Women's Hospital. Here are a just a few of those buildings:

* Chicago City Hall--The winner of the American Society of Landscape Architects 2002 Professional Merit Award saves the city $5,000 a year on utility bills, according to Johnston. The roof is home to roughly 20,000 plants, including 112 woody shrubs, as well as Cockspur Hawthorn and Prairie Crabapple trees. "Hundreds of thousands of people look down on the prairie-style rooftop," Johnston says. "It creates an area of beauty in the city that people can appreciate from out of their office windows, and that's difficult to quantify, but it makes life more attractive for humans and wildlife."

* Millennium Park--The winner of the 2005 Green Roofs for Healthy Cities Awards of Excellence in the Intensive Industrial/Commercial category is considered one of the largest green roof projects in the world. It's considered a green roof because it sits at grade over a parking garage and railroad tracks. The 24.5-acre park, which cost $475 million, features the Frank Gehry-designed Jay Pritzker Pavilion, Jaume Plensa's interactive Crown Fountain and Anish Kapoor's Cloud Gate--or the "Bean" sculpture.

* Schwab Rehabilitation Hospital--The winner of Green Roofs for Healthy Cities' 2005 Intensive Institutional Award is used as part of the 120-bed physical medicine and rehabilitation hospital's therapeutic process. More than 60 different drought-resistant Midwestern savanna plant species cover the building's roof. Many of the species were selected for sensory stimulation, such as lavender's strong, calming scent, blue fescue's piney texture and orange meadow bright's striking orange color and citrus scent. "Before we installed the garden [in 2003], we were treating patients in a traditional gym setting...now we use the garden for sensory stimulation whether its touch, tactile or textile stimulation, or to develop fine motor skills while gardening, planting or watering," says Michael Wehner, a senior recreational therapist at the hospital. "Patients really respond to the garden's beauty and the sun, along with the [garden's] waterfall and pond and over 60 species of plants."

* Target--Three of the low-cost retailer's Chicago locations feature green roofs that are inaccessible to the public, as they are aimed at lowering the store's electric costs. In 2004, Target installed a 10,000-square-foot green roof at 2939 W. Addison St., as well as a 7,128-square-foot green roof at its store at 1154 S. Clark St. However, both those roofs pale in comparison to the retailer's 45,963-square-foot roof atop the Target at 1940 W. 33rd St.

* McCormick Place Convention Center West Building--The Metropolitan Pier and Exposition Authority (MPEA) aims for its new 2.3 million-square-foot McCormick Place Convention Center West Building, which is set to open this year, to become the largest building in the country to achieve U.S. Green Building Council LEED (Leadership in Energy and Environmental Green Building) certification. The LEED Rating System is the nationally accepted benchmark for the design, construction and operation of high performance green buildings. "We wanted to be environmentally friendly because we thought it was the right thing to do," says Laura Tagler, the building's senior development manager. When the building is finished, Tagler says the more than 130,000-square-foot roof will not only contribute to a better environment in Chicago, but also will lead to significant savings for the MPEA.

Published: April 01, 2007
Issue: Spring 2007