City Roofs Are in Blossom, Corporate Buildings Abloom

Submitted by Louisa May

Butterfly effectThe cities of Chicago, Atlanta, Portland, and Seattle have something in common these days, and this commonality embraces not only civic responsibility for improving the environment but the idea that small effects can lead to big changes. 

This idea is known as the “butterfly effect,” or the beginning of chaos theory. A scientific concept proposed by MIT professor Edward Lorenz in the 1960’s, this example illustrates sensitive dependence on initial conditions. Something as minuscule as a butterfly flapping its wings in Brazil changes the constantly moving atmosphere in ways that could trigger a tornado in Oklahoma.  

Green roofSo, too with rooftops. A green rooftop in Argentina can affect the quality of life for swallows returning to the Mission in San Juan Capistrano and enhance the oxygen cycle for people living in L.A. Rooftops are turning green with more and more frequency now that ecologists, architects, and manufacturers are beginning to learn from each other. 

A green roof is a roof of a building that is at least partially covered with vegetation and soil, and its most basic design is dirt and grass planted over a waterproof membrane such as rubber. But green roofs aren’t just for chicken coops and storage sheds anymore. Professional green roof systems were developed in Germany in the 1960’s and have just taken awhile to catch on in the US. Today, sophisticated green roofs are appearing everywhere across the country. 

One high profile green roof apartment complex is The Louisa, a residential high rise apartment building in downtown Portland, Oregon. The Louisa has 242 apartments including ground floor retail and showcases extensive and intensive green roof systems.The intensive portion of the roof is one hundred percent accessible. This allows residents to gather for outdoor parties and barbecues. Drought resistant and native species plants freshen the air, improve the view, and offer pleasing green relief to neighbors viewing from outside the complex. The total cost of the green roofs including membrane, insulation, drainage growth medium, irrigation pavers, and plants was $15.00 per square ft. for the extensive portion and $25.00 per square ft. for the intensive portion.The building is LEED certified.The LEED (Leadership in Energy and Environmental Design) certification is a green building and third party rating system. It measures building sustainability and promotes design and construction practices that are profitable and environmentally responsible.     

City Halls in Atlanta and Chicago, GAP headquarters in California, and Seattle’s King County Airport also sport green roofs. All of these systems are constructed in layers over metal or concrete roof decks. Besides the necessary waterproof membrane or thermal barriers, the layers consist of drainage composites, insulation, filter fabrics, growth medium, and vegetation.The layers differ depending on whether the rooftop deck is metal or concrete.  

In 2001, Chicago’s City Hall roof garden was completed. It was designed as a test to determine what impact green roofs would have on reducing the urban heat island (UHI) effect. The UHI is a metropolitan area that becomes significantly warmer than the area surrounding it due to the density of concrete, metal, and asphalt surfaces. Chicago’s next project was considerably larger: the $480 million dollar Millennium Park is an extension to Grant Park. Sitting at grade above two parking garages, it is considered an intensive green roof, and it is currently one of the world’s largest at 24.5 acres. Inviting and luxurious with full grown trees, this area is completely open to the public, has its own transit center, and comes complete with ice- skating rink and a 1,525 seat performance center. The project won the 2005 Green Roofs for Healthy Cities Award for Intensive Industrial Commercial Category.

There are intensive and extensive systems (think labor- intensive or self- sustaining here) with the intensive adding 80-150 pounds per square foot of load to a building structure and the extensive adding only 12 to 50 pounds per square foot depending on the soil characteristics and substrata. If this sounds like a lot of work and money, it is, but the benefits are measurable and good for the Earth.  

Designed to curb air pollution, reduce storm water run-off, and decrease energy expenses, these rooftops offer us a lesson in ecosystems as well. Sometimes plants die or roofs leak, but when this happens, a lesson is learned and the next round of green roofs are better; people become better informed.

Interconnectedness is what green roofs are all about and reflect, too, what our communities are all about. The late Edward Lorenz came up with the theory, but we are learning new ways to apply it. The blossoming of green roofs expresses beautifully the idea that small effects do lead to big changes.

Check out our Green Pages for information on money saving tips that help the environment.  Once there, click on the Green Forum to see more articles by our green feature writer Louisa May.

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