Photo: Edmund C. Snodgrass
Green roofs go a long way toward helping to create a more sustainable world. While it may seem an unusual building technique, green roofs go back as far as 600 B.C. to the hanging gardens of Babylon in Iraq, built by King Nebuchadnezzar for his wife, Queen Amyitis, who longed for the tropical gardens of her Persian homeland. The gardens were terraced from the top of their palace to the ground, providing all the fruits and flora she missed. According to legend, the palace and their gardens were destroyed by earthquakes.
In past decades, green roofs have become popular in Europe. Today, building regulations in Germany and Canada support green roof development because of its improved sustainability, longevity, and thermal and water-filtering qualities.
Now green roofs are gaining ground in the United States, too. Chicago Mayor Richard Daley vowed that Chicago would be the city with the most turf on its concrete skyline, greening City Hall in 2001. Currently, the city has achieved his goal of more than 300 buildings – 7,000,000 square feet – of green roofs completed or under way. Washington, D.C.; Minneapolis; and Baltimore also stand out as leaders in the green roof revolution, according to www.greenroofs.org, the website of Green Roofs for Healthy Cities. This organization provides resources and education to help guide the way to rooftop sustainability.
The steep slopes of the roof at the California Academy of Sciences act as a natural ventilation and cooling system.
Photo: Courtesy of Green Roofs for Healthy Cities (www.greenroofs.org) and Rana Creek Living Architecture.
The U.S. Green Building Council® (USGBC®) announced a new award in September 2010, titled the "Mayor Richard M. Daley Legacy Award for Global Leadership in Creating Sustainable Cities." Mayor Daley was its first recipient, at the USGBC Greenbuild conference (November 17-19, 2010) in Chicago. USGBC said Chicago's Sustainable Development Policy mandates that projects receiving financial or zoning assistance from the city include sustainable elements such as green roofs, LEED® certification, or designs that allow structures to absorb large amounts of stormwater.
Chicago's Green Permit Program allows contractors to shave off as much as $25,000 from the building permit process by choosing to incorporate some of 12 sustainable design elements.