Improving Life in Chicago: Green Roofs

by: Andy Angelos

The urban core of Chicago is home to a number of green roofs, most notably the 20,300 square feet atop City Hall. Completed in 2001, the green space provides a laboratory for variations of plants, soil mixtures, and environmental impact. More recently, The Residences at 900 in the Gold Coast neighborhood received a 2008 Green Roof Award of Excellence for 14,000 square feet of converted green space.

Adding vegetation to the city’s building tops has many benefits including cleaner rainwater, lower air temperatures, improved air quality, and added longevity for the roofing membrane. Not surprisingly, Chicago officials hope to spread these benefits and offer up to $5000 grants for installing green roofs.

Aside from contributing to a more interconnected urban-nature relationship, the surge in Chicago Green roofs has also provided the region with expertise in constructing eco-friendly roofs and studying urban heat islands. A generic green rooftop construction requires six to seven layers including protective membranes, drainage assistance, and a soil layer. Depending on the selection of plant life and soil, the cost varies from 5 to 35 USD per square foot. After implementation, the green space begins to mitigate effects from the Urban Heat Island phenomenon. Greenery on building tops is capable of reflecting some of the heat typically absorbed by metal, concrete, or asphalt surfaces. The net effect is lower temperatures for Chicago and surrounding regions.

Do you know of any other examples of Green Roofs in Chicago? If so, feel free to send pictures or details our way to show the world how Chicago is altering its urban fabric.