High above Chicago’s busy finance district, a rooftop island of greenery stands out among its neighbor buildings. Covered with grasses and plants, the Chicago City Hall is a heaven, especially on a hot day when the temperatures on the black asphalt of neighbors roofs soar.
“You can feel the difference in summer” said Kevin Laberge of the City of Chicago’s Department of Environment. “One roof is big, empty and unused while the other is providing a habitat for wildlife, reducing temperatures and retaining storm water”. Chicago’s City Hall has a green roof, a planted rooftop with system of waterproofing, insulation, and a layer of grow medium used to conserve energy and to contribute to a more healthy environment.
More city planners, architects and civil engineers around the world are turning to green roof technology because it makes environmental and economic sense. Most notably, in Chicago, it saves the city almost $10,000 annually in energy costs. During summer and winter months, the roof exhibits superior insulation properties, requiring as much as 30% less from City Hall’s heating and air-conditioning systems over the last four years.
Additionally, the green roof reduce storm water runoff by absorbing as much as 75% of the rainwater that fall on it, lightening the load of Chicago’s sewer system. Improved air quality and a reduction in noise pollution by as much as 40 decibels as compared to a traditional flat roof are also typical to green roofs like the City Hall’s.
Finally, planted roofs extend their own life by moderation temperture swings that can lead to additional wear and tear on an exposed roof in climate like Chicago’s. Where the average life expectancy of an exposed roof may be 20 years, green roofs can be expected to las considerably longer.
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