American cities have a surprising amount of wasted open space. Even in densely packed urban areas like New York City, the prime real estate atop roofs is given much less consideration than one would expect from a populace that values each square foot of space so highly. This oversight is a real shame, because there is so much that can be done to improve the local environment and quality of life, simply by fixing up a roof.

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The average city rooftop is layered with black tar, a material which traps sunlight and heat, raising the temperature of the surrounding area. The heat trapped by dark, flat roofs elevates city temperatures as much as ten degrees Fahrenheit – contributing to what scientists call the “urban heat island” effect.

Cool Roofs The easiest and quickest solution to combat the urban heat effect is simply to turn hot dark roofs into “cool roofs” by painting them with a basic coating of light-colored water sealant. In the same way that white clothing helps keep you cool in the summertime, white roofs reflect sunlight and heat. If all the roofs in New York City were ?cool roofs?, the city would save some $100 million dollars per year in cooling costs.

Green Roofs An even better alternative to cool roofs (albeit one that requires more time and effort) is to turn waste roofs into landscaped Green Roofs. Green roofs having the same cooling effect of white roofs, with the added benefits of:

* Providing amenity space for building users ? replacing a yard or patio * Increasing roof life span * Reducing storm water run off * Providing noise insulation * Filtering pollutants and CO2 out of the air * Providing locally grown food (with roof-top vegetable gardens) * Increasing wildlife habitat in built up areas * Reducing heating (by adding mass and thermal resistance value) and cooling (by evaporative cooling) loads on a building * Reducing the urban heat island effect

Cost & city planning Green roofs add so many benefits to a building and its surrounding area, it’s astonishing that more roofs aren’t green at this point. The biggest roadblock to our green roof future seems to be cost and bureaucratic red tape of city planning laws. Although green roofs cost more up front to install than regular roofs, the savings that they accrue over the years quickly pay off. The biggest hurdle to getting green roofs going in more places, is convincing getting city governments to change their policies and adopt programs which provide incentives to property owners to renovate their roofs.

In this endeavor, the city of Chicago is leading the way. Chicago’s Department of Environment is actually giving away $5,000 grants to any building owners who want to start a green roof project. So if you are a lucky homeowner living in Chicago, you have no excuse for not making your rooftop green!

Meanwhile I’m waiting for New York City to wake up and get on the ball with this. If only this photograph were more than just an “artist representation”

Aesthetics Frustratingly, another hurdle to green roof world-domination is the fact that ever since the “back-to-the-earth” straw bale movement of the seventies, green roofs have been associated with a sloppy, crunchy aesthetic. This is an unfair and unfortunate connotation, since green roofs can be as clean, modern, and integral to ?good? architecture as glass and steel. Peter Zumthor’s green roofs on the Val Thermal Baths in Switzerland are just one example of a stunning use of green roofing in contemporary architectural design.

Others include Renzo Piano’s proposed redesign of the California Academy of Science in San Francisco. Piano’s green roof design features mounds and valleys of various heights and sizes, creating pockets of shade and opening vistas into the surrounding Golden Gate Park.

The largest “living roof” in the world was designed by environmental architect William Mcdonough, and sits on top of the the Ford Motor Company’s Rouge Manufacturing Plant in Dearborn, Michigan. Other notable green roofs include the international airport in Amsterdam, and the sloped green roofs of the Palais Omnisports in Paris-Bercy.

For more information on Green Roofs check out:

+ Greenroofs For Healty Cities +

Also, Treehugger posted a fabulous Green Roof Primer back in September. With an extensive collection of photos and diagrams, this helpful primer documents Treehugger volunteers putting up a green roof over a yoga studio in Toronto.