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Rooftop Gardens Springing Up in Chicago as Solution to 'Heat Island Effect' - 2002-06-17

On the nightly TV news in large American cities, the meteorologist sometimes talks about the 'heat island effect'. That's a phenomenon whereby all the blacktop roofs and asphalt parking lots in an urban area soak up the heat from the sun and increase the temperature on a hot summer day. Chicago has taken it upon itself to do something to reduce that effect. To set an example, the mayor decided to start with City Hall.

Standing on the roof, eleven stories up, isn't really far enough to escape the noise of the city below. But this rooftop is an escape. It's a garden, a big one. There are even trees. Not in pots, but actually planted on, or rather in, the roof.

Marcia Jiminez is the Commissioner of the City of Chicago's Department of Environment. She says Chicago wants building owners to do what they can to cool the city down, and planting gardens on the roof is one way to do it. So that's what the city did on top of City Hall. "Well," she said, "the garden on the rooftop is addressing what we call an urban heat island problem. By putting the garden with light colored pavers and the green plants on top of the roof, we're actually helping to use less energy inside the building and it actually helps to keep the building cooler."

Cooling down the building is just the beginning of this garden. Despite being eleven stories up and in the middle of downtown, the roof is alive with bugs and butterflies. "Actually, birds and all of the insects, many of them, have found their way up here. We've actually put up birdhouses to study what kind of birds are coming to the rooftop garden. This is a place of respite as well as a place to feed [for the birds]."

The whole rooftop has become something of a laboratory. Scientists research what animals have made a home here, and they're monitoring how the plants are spreading.

Kimberly Worthington worked on the City Hall project from the drawing board to completion. She says they chose plants for color, form and for durability.

"The design that we went with was low maintenance, that was what we were looking for in our plant selection," she said. "The landscape architects that were part of the design team focused on plants that would require less water, and they also wanted to keep as many native plants as possible. As a result, there are a lot of prairie plants up here."

The Chicago City Hall rooftop project also reduces rain water runoff. Out of one inch of rainfall, 75 percent will be soaked up in the garden, curbing problems with overflowing water drainage and sewer capacity. Theoretically, if enough buildings in the city had rooftop gardens, storm water runoff problems could be reduced considerably.

While the city is touting the environmental benefits of its rooftop garden, in another part of the city a planned rooftop garden is all about people.

Brenda Koverman is with the Schwab Rehabilitation Hospital in Chicago. The rooftop garden that is under construction. The garden, while reaping all of the environmental advantages of city hall, is focused primarily on the aesthetic qualities that the open air and plants will provide for patients, instead of the sterile hospital decor. Once the garden is completed, she says, the hospital will be able to see how the garden effects patient's recovery. She says of the project, "Are patients more able to maneuver their wheelchairs in the community? Are patients able to use their hands better so they can cook better at home? Are patients able to stay out of the nursing home and go to their home? If we can get any kind of those outcomes, then it's a huge success."

There aren't very many of these projects in the city, so it's hard to say whether the rooftop gardens could cool things down all that much. But Environment Commissioner Marcia Jiminez says that the results speak for themselves. City Hall, for example, is directly adjacent to the County Building, but according to Jiminez's testimony, "Last summer, in 2001, on the hottest day, while it was about a 100 degrees on the City Hall side, it was 165 degrees on the opposite end of the building where's there's a blacktop roof."

Even if you're not interested in planting a garden on your roof, the city still requires some effort to cool things down. City ordinance now requires all new roofs to have light colored material on the surface, and parking lots have to plant a certain number of trees before they can get a permit to resurface. Rooftop gardens aren't mandatory, but city officials say they're learning first hand that it's a much better use of space in the city.