Conscious Choice: Why Green Roofs Rock

October 2006 | Ask the Green Commish

Why Green Roofs Rock

By Sadhu A. Johnston

Dear Green Commish: Can you explain what a green roof is and why is there so much attention given to them? — Muy Curiouso?

Dear Curiouso: As the Commissioner of the Chicago Department of Environment, I have a view (both literally and figuratively) that makes my job very rewarding. I have the privilege to work with a dedicated group of people who strive to improve the quality of life in Chicago, and I also can look out of my office window and down on one of the most beautiful rooftop gardens you will find anywhere in the country.

One of the most high-profile examples of Mayor Daley’s commitment to the “greening of Chicago” and making the city healthier and more environmentally sustainable, is the garden on the roof of City Hall.

Why the buzz about green roofs? Green roofs:

• Combat the urban heat island effect. Heat islands develop as cities replace natural land cover with pavement, buildings, and other infrastructure, resulting in increased temperatures in cities as high as 10 degrees. Green roofs reduce the urban heat island effect through shade and evapotranspiration, the release of water from plants to the surrounding air.

• Mitigate stormwater impacts. The City Hall garden acts as a giant sponge, absorbing 75 percent of a one-inch rainfall, preventing water from entering the sewers. Two 150-gallon cisterns also retain rainwater for later use. Rainwater is a valuable resource and its reuse is a critical component of Mayor Daley’s Water Agenda.

• Reduce energy costs and the load on the entire electrical system. Dark surfaces absorb heat, requiring more energy to cool a building’s interior. On hot summer days, the surface temperature of a vegetated rooftop can be cooler than the air temperature, whereas the surface of a traditional rooftop can be up to 90 degrees °F.

• Longevity. Green roofs can last up to 30 years longer than a standard roof, which lasts an average of 15 years. The vegetated elements of a green roof protect the substrate from damaging UV radiation, as well as lessen daily temperature fluctuations, which cause repeated contraction and expansion on traditional roofs.

Green roofs also provide an aesthetic benefit, as well as a habitat for wildlife. The rooftop garden at City Hall has beehives (installed in 2003) and the honey bees help pollinate the plants and produce impressive quantities of honey which is sold to benefit the youth program Gallery 37. Ten birdhouses attract wildlife such as finches, chickadees and wrens. The garden is also home to monarch butterflies and grasshoppers.

Since the Spring of 2000, when the City began construction of the 21,000 square foot rooftop garden at City Hall, the City has led by example and encouraged both the public and private sectors to adopt green roofs as part of Chicago’s overall environmental strategy. Just last month, Mayor Daley unveiled Chicago’s latest green roof atop the Chicago Cultural Center complete with solar thermal panels.

The City will again offer grants to residents and small business owners to help with the installation of green roofs (last November, the Department of Environment awarded $100,000). Building on that success, $200,000 in grant funds were made available last month. Application forms are available at cityofchicago.org/environment or from the Department of Environment, 30 North LaSalle Street, 25th Floor. Applications are due Friday, November 3, 2006.

The City has a number of programs to encourage and, in some cases, require the installation of green roofs. The Department of Construction and Permits began a Green Permit Program in 2005, which expedites a permit when a building incorporates green elements, including green roofs. This past June, the Chicago City Council approved an ordinance that provides matching funds for green roofs on downtown buildings.

Check out the benefits yourself! You can find green roofs at the award-winning Chicago Center for Green Technology, the Peggy Notabaert Nature Museum, the Schwab Rehabilitation Center and the Rock and Roll McDonald’s. The next time you’re enjoying one of the many programs at Millennium Park, look down—you’re standing on the largest green roof in the country!

The City of Chicago continues to receive much green publicity. More often than not, the green roof initiatives receive the lion’s share of recognition, but they are only part of an overall strategy to make Chicago the most environmentally friendly city in the country.

Sadhu A. Johnston, is commissioner of Chicago’s Department of Environment, which administers programs to protect and restore Chicago’s natural resources; reduce waste; clean up brownfields; promote energy efficiency and reliability; educate the public about environmental issues; and enforce the city’s environmental protection laws.

Got a question for the Environmental Commissioner? Email the editor. Please put Green Commish in the subject line. Or via regular post to Green Commish, Conscious Choice, 920 N. Franklin, Suite 202, Chicago, IL, 60610. Letters may be edited for clarity and brevity.

Recommend this page to a friend

Top Ten pages recommended to friends: