Chicago City Hall
Green roofs: taking root in the US
Whilst the Bush administration buries its head in the sand on climate change, cities such as Chicago and New York are addressing the threat and embracing green design. Kirsten Jellard looks at the growing emergence of roof gardens in the US and examines their environmental and economic benefits.
From Ryker’s Island Prison in New York to the US Food and Drug Administration building in Washington DC green roofs are sprouting all over the United States. Industry association Green Roofs for Healthy Cities recorded a 80 percent increase in green roofs planted between 2004 and 2005 and the trend is growing.
People have been greening their roofs since the dawn of time. The most famous green roof or really overhanging garden, The Hanging Gardens of Babylon are believed to date back to 600 BC. Vikings frequently covered their homes in turf and Egyptians grow plants and food on their buildings. Today green space is intricately connected with city planning.
People have been greening their roofs since the dawn of time. The most famous green roof or really overhanging garden, The Hanging Gardens of Babylon are believed to date back to 600 BC. Vikings frequently covered their homes in turf and Egyptians grow plants and food on their buildings. Today green space is intricately connected with city planning.
What is a green roof?
A green roof replaces traditional roofing materials with a lightweight living system of vegetation. In contrast roof gardens tend to be decorative and heavier. Modern green roof technologies originated in Germany, where about 12 percent of roofs are green. In 2001, Tokyo passed an law requiring new buildings to devote at least a fifth of their rooftops to greenery. But Germany, Japan and Switzerland are the only countries that currently require vegetation on some of their buildings.
'The greenest city in America'
Chicago, the mid-west’s windy city and home to the University of Chicago, where the term ecology was coined, leads the US green roof movement with over 200 green roofs. Sadhu Johnston, Chicago’s environment commissioner estimates that 'Chicago has more green roofs than the rest of the country put together' with businesses as diverse as McDonald’s and an Apple store, as well as private residences, proudly contributing.
Chicago City Hall is one of the earliest and most well known examples of a green roof in the United States. Completed in 2001 after Mayor Richard Daley vowed to make Chicago 'the greenest city in America', it was built as a test for a US Environmental Protection Agency’s green roof study of urban heat island effect and air quality.
Urban heat island effect, which can make cities hotter than their surroundings, is not a new phenomenon. But as cities grow, there is increasing concern over whether this additional warmth will further impact global temperatures.
Greenery in general cools its surroundings, but green roofs also absorb less heat. At City Hall results from the first green-roofed summer showed a roof surface temperature reduction of 30+ degrees Celsius, over neighbouring roofs, and an air temperature reduction of about 9 degrees Celsius. It is estimated that if all the roofs in a large city were greened metropolitan temperatures could be lowered significantly. The green roof helps keep City Hall warm in winters too. Overall, heating and cooling costs and energy usage are greatly reduced.
Tokyo-based Organization for Landscape and Urban Greenery Technology Development is passionate about energy and money savings. It estimates that if half Tokyo’s roofs were greened, the city could save nearly £500,000 (¥110 million) on air conditioning costs daily!
Chicago City Hall is one of the earliest and most well known examples of a green roof in the United States. Completed in 2001 after Mayor Richard Daley vowed to make Chicago 'the greenest city in America', it was built as a test for a US Environmental Protection Agency’s green roof study of urban heat island effect and air quality.
Urban heat island effect, which can make cities hotter than their surroundings, is not a new phenomenon. But as cities grow, there is increasing concern over whether this additional warmth will further impact global temperatures.
Greenery in general cools its surroundings, but green roofs also absorb less heat. At City Hall results from the first green-roofed summer showed a roof surface temperature reduction of 30+ degrees Celsius, over neighbouring roofs, and an air temperature reduction of about 9 degrees Celsius. It is estimated that if all the roofs in a large city were greened metropolitan temperatures could be lowered significantly. The green roof helps keep City Hall warm in winters too. Overall, heating and cooling costs and energy usage are greatly reduced.
Tokyo-based Organization for Landscape and Urban Greenery Technology Development is passionate about energy and money savings. It estimates that if half Tokyo’s roofs were greened, the city could save nearly £500,000 (¥110 million) on air conditioning costs daily!
More than an attractive view
Cities have many impermeable surfaces and during heavy rains storm water run off from these surfaces can overwhelm the sewage system, straining pipes and infrastructure and allowing untreated water to flow into rivers. This has become a major problem in many US east coast cities. Previous solutions included building bigger pipes, but this offers no environmental or aesthetic benefits.
Enter green roofs. Because much of the water falling on a green roof is absorbed and later evaporates as water vapour, green roofs offer a 'soft approach, an environmentally green approach, to the storm water' problem, says David Beattie, Director of Pennsylvania State University's Center for Green Roof Research.
This approach has proven successful at the world’s largest green roof on the Ford Motor Company’s truck plant in Dearborn, Michigan. Covering 10.4 acres, that massive green roof is estimated to absorb 4 millions gallons of rainwater per year significantly reducing storm water runoff into the nearby river.
Green roofs can also provide a source of local food – why not grow veggies overhead? - and could be designed to mimic endangered ecosystems. They attract wildlife and provide habitat where there might otherwise be limited green space.
Sustainability is a consideration for Chicago City Hall which auctions honey that is produced from beehives on its green roof. Suburban store True Nature Foods plans to completely eliminate food miles by installing a roof top vegetable and herb garden. This will support the local economy, ensure fresher produce and is a truly successful model of sustainability.
The success story of City Hall’s green roof has inspired Chicago to implement ‘green requirements’ for buildings constructed with public money, or those near Lake Michigan. Incentives are offered to builders who include green roofs in their designs. As Mayor Daley states, 'we're aggressive in terms of the environment and we're educating the people and bringing business along."
And, it’s not only energy saving, storm water reduction and aesthetics which give green roofs their appeal. A green oasis in the sky can also heal you. Tokyo community architect Shuji Koshikawa believes 'city dwellers have a real need for the healing of green in their life'. Green roofs are the ultimate solution. They are attractive, nourishing and restorative, and offer a lush refuge from the concrete jungle.
Enter green roofs. Because much of the water falling on a green roof is absorbed and later evaporates as water vapour, green roofs offer a 'soft approach, an environmentally green approach, to the storm water' problem, says David Beattie, Director of Pennsylvania State University's Center for Green Roof Research.
This approach has proven successful at the world’s largest green roof on the Ford Motor Company’s truck plant in Dearborn, Michigan. Covering 10.4 acres, that massive green roof is estimated to absorb 4 millions gallons of rainwater per year significantly reducing storm water runoff into the nearby river.
Green roofs can also provide a source of local food – why not grow veggies overhead? - and could be designed to mimic endangered ecosystems. They attract wildlife and provide habitat where there might otherwise be limited green space.
Sustainability is a consideration for Chicago City Hall which auctions honey that is produced from beehives on its green roof. Suburban store True Nature Foods plans to completely eliminate food miles by installing a roof top vegetable and herb garden. This will support the local economy, ensure fresher produce and is a truly successful model of sustainability.
The success story of City Hall’s green roof has inspired Chicago to implement ‘green requirements’ for buildings constructed with public money, or those near Lake Michigan. Incentives are offered to builders who include green roofs in their designs. As Mayor Daley states, 'we're aggressive in terms of the environment and we're educating the people and bringing business along."
And, it’s not only energy saving, storm water reduction and aesthetics which give green roofs their appeal. A green oasis in the sky can also heal you. Tokyo community architect Shuji Koshikawa believes 'city dwellers have a real need for the healing of green in their life'. Green roofs are the ultimate solution. They are attractive, nourishing and restorative, and offer a lush refuge from the concrete jungle.
Further reading
Have a spare patch of roof? BBC Gardening can help you build your very own roof garden.
And if the sky really is the limit have a bespoke roof garden crafted for you by the experts at Urban Roof Gardens.
Additional UK information on green roofs can be found at Living Roofs.
Join the climate change campaign
And if the sky really is the limit have a bespoke roof garden crafted for you by the experts at Urban Roof Gardens.
Additional UK information on green roofs can be found at Living Roofs.
Join the climate change campaign
 |
|
|
Terms & Conditions © Christian Aid 2007