I’ve often walked around Chicago in the peak of summer, only to feel the pavement underneath my feet feel as if it sizzling in the beating sun. It’s hot. I literally feel like a piece of frying bacon on the sidewalk sometimes. It’s a heat island.
A heat island is a built-up area which is consistently hotter than its surroundings, particularly in the summer. The heat island effect is caused mostly by the difference between the generally dark surfaces of a city like roads and sidewalks and the vegetation it’s replaced. These dark surfaces absorb sunlight, heat up, and retain more heat than open space areas. Add hot air from vehicle exhausts and industry, the temperature rises even more.
There is one place that I know of that is high above the pavement of the city streets and it’s still cool. It’s the green roof on top of City Hall. In 2001, it was completed and took this large underutilized space in the thick urban Chicago jungle and created an oasis of green living. The 20,300 square foot City Hall rooftop garden has over 20,000 native plants that were installed as plugs of more than 150 varieties. Although rainwater is collected and saved, a supplemental irrigation system aids in establishing the plants as well as provide supplemental water during extreme periods of drought. Pretty neat, huh?
I wondered about the inside of the building and so I asked a few members of the staff about their thoughts on the green roof. Did it make a difference? All agreed that it insulates the building, making it warmer in the winter and cooler in the summer. They also noticed that when they walk out of the building, immediately there is a cool breeze surrounding the building before they step further out into the thick humidity of the day.
If a green roof is helping change the heat island effects in one part of Chicago, think about what it could do if they were all over the country. Communities can take a number of common-sense measures to reduce the effects of summertime heat islands. You can help!
To find out more, go to http://www.epa.gov/heatislands/index.htm
Yvonne Gonzalez is a SCEP intern with the Air and Radiation Division in Region 5. She is currently pursuing a dual graduate degree at DePaul University.