Did you know...
Modern greenroofs, which are made of a system of manufactured layers deliberately placed over roofs to support growing medium and vegetation, are a relatively new phenomenon. They were developed in Germany in the 1960s, and have since spread to many countries. Today, it is estimated that about 10% of all German roofs have been “greened.” Greenroofs are also becoming increasingly popular in the United States, although they are not as common as in Europe.
Greenroofs are becoming common in Chicago, as well as Atlanta, Portland, and other cities, where their use is encouraged by regulations to combat the urban heat island effect. In the case of Chicago, the city has passed codes offering incentives to builders who put greenroofs on their buildings. The Chicago City Hall greenroof is one of the earliest and most well known examples of greenroofs in the United States; it was planted as an experiment to determine the effects a greenroof would have on the microclimate of the roof. Following this and other studies, it has now been estimated that if all the roofs in a major city were "greened," urban temperatures could be reduced by as much as 7 degrees Celsius.