Green walls of China

Vertical vegetated walls are popping up in cities throughout Asia.

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PlentyMag.com

Tue, Apr 14 2009 at 3:50 PM

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Green Building, Green Design

Photo: thingermejig

As green roofs continue to top off buildings in the U.S., other visible but equally verdant structures are sprouting in many Asian cities.

In Hong Kong, Singapore, and Tokyo, for example, vegetated layers are lining the exterior walls of some high-rise buildings. This is the result of beefed-up efforts at vertical planting, also known as green walls. Just think of them as vertical green roofs—and like the ever-popular roofs, green walls boast environmental benefits like filtering out air pollutants and helping to cool down cities.

In many ways, vertical planting is better suited to the Asian cities than horizontal planting. For one thing, the super-dense cities don’t leave much room for greenery. A green façade or sidewall, however, takes no inches of real estate. Meanwhile, the concrete, steel, and glass towers that dominate central business districts in these cities has created a craving for visibly verdant sights. A green roof on an 80-storied skyscraper doesn’t cut it, but an external wall of ferns and mosses can serve as eye candy while also helping the environment.

“Hong Kong is a vertical city. There are lots of opportunities to do vertical planting in Hong Kong,” says C.Y. Jim, professor of geography at the University of Hong Kong (HKU), who has been testing native plants best suited for vertical growth. “It’s a matter of changing people’s mindset.”

Change is certainly coming: In March, the city’s urban renewal officials announced that they would collaborate with developers to foster vertical planting in city-controlled redevelopment areas, contingent on site conditions. This initiative came on the heels of last year’s opening of the city’s largest green wall in a new shopping and residential complex.

The complex, Vision City in the Tsuen Wan district, is aimed to be developer Sino Land Company’s latest major environmentally friendly project. The complex’s signature green element is the 7,500 square foot curved green wall facing the inner courtyard of the shopping mall. The living wall hangs nearly 60 feet above ground to clad the concrete columns of a two-storied parking garage. Nearly the size of a standard championship tennis court, the wall offers a green vista of plants that filter and cool the air—sans electricity—to residents and visitors at the piazza.

Three of the six species chosen to fill the wall, including Boston ferns, are known to trap air pollutants, says Thomas Lau, the landscape architect who supervised the wall’s design. Data is currently being collected to gauge the wall’s cooling effect. Research on vertical planting, done mostly by Japanese building experts, showed that a layer of green can lower ambient temperature by as much as 10 to 20 degrees Celsius, though the cooling varies according to surrounding wind speeds and the amount of shade available.

Though it might seem like a simple structure, green walls can be quite complex. Because of its height, the Vision City wall called for steel frames specially designed to support planters and the wind load, but the most painstaking calibration lay in the irrigation system. Hundreds of trials were run to ensure appropriate water supply to the nearly 40,000 plants that make up the verdant wall. Even now, six months after completion, that is still a big part of the wall’s maintenance, along with fertilization and weeding.

“The challenge is to monitor the water flow,” says Lau.

Hong Kong isn’t the only city building green walls. In fact, Japan has been a pioneer in planting vertically since the 1970s, says Stephen Lam, a HKU academic specializing in sustainable architecture who is under commission by the Hong Kong government to study the environmental benefits of green walls. He also notes that Japanese households can buy modular green wall units and install them at home, and Singapore has been installing green walls on its highways’ structural supports.

Citing earlier research by scientists at Waseda University in Tokyo, Lam says while a green wall’s planting typically is not thick or dense enough to yield noticeable carbon offsets, its reduction to the urban heat island effect is significant. Unlike most rooftops, not all external walls are suitable for planting, depending on their amount of sun exposure. The walls’ aesthetic value and positive psychological effect on city dwellers, albeit less measurable, are also worth noting, Lam says.

Story by Violet Law. This article originally appeared in "Plenty" in April 2008.

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Comments: 3

Uncle B May 17 2009 at 10:56 AM

Humanure! Yes, we need to bio-gas humanure and use the remaining sludge (irradiated for safety?) for gardens! As the end of the "Cheap Oil Era" comes upon mankind, resource flows we never thought valuable, even algae in sewage ponds, will become priceless, and we need to be ready, before the crunch, to grow even on building walls and ugly cement installations, plant forms that replenish and ameliorates our environment, and provide us food and fuel. Sooner than we like, many Americans will be unemployed

.... More

or under-employed, and the old American Dream as it dies will give to the world a new environmentally friendly and sustainable life-style. We will, of necessity, eat no beef, more veggies, some aquacultured fish, lots of grains and drink pure water if we can find it. Smaller battery powered cars (rebuildable, no planned obsolescence allowed, recyclable batteries) will prevail, rail travel will become popular, airplane travel obsoleted, and telecommuting, to work, around the world, will take hold. Fission-Fires will be banned world wide after the first Chinese accident, at any one of their eleven new reactors being built as we speak, and the "Yuan" is rapidly becoming the money of world trade, displacing the over-manipulated U.S. dollar, and forcing many archaic American notions about life-styles out with it. A greener world with more renewability and sustainability, backed by a well regulated and modified capitalism and a new corporate definition is coming out of Asia, and China in particular, and this will force the current U.S. based unregulated vulture capitalism to the side, leaving room for a greener, slower, less vicious and exploitive world, where a backyard garden, personal aquaculture installations, greenhouses and education will define an individual's riches, not McMansions, SUV's, and possessions. In the new "Post Materialist Meritocracy" wars will be fought through economics, now that the Chinese communists have proven its effectiveness, and less money spent on military adventures will divert cash to science and the arts, as we were before the America's were populated. Populations will be controlled much as they are in China today, and American rampant irresponsible sexuality for entertainment purposes will diminish and dissolve into a more normal, humane, less publicized, and natural process. Large cities will crumble, small "Pods", or villages of people, interdependent and self-sufficient, interconnected by wireless communications will evolve, and save for large medical centers and Universities, most people will live out their lives in stable eco-sane, survival shelters with zero maintenance, zero running costs due to design. A larger portion of physical labor will be required of each individual, and selective breeding for small body size, high intelligence and resilience will occur. All potential for greens will be utilized, technically advanced, and developed towards the goal of sustainability for the community, The individual,and his greedy desires, once catered to by the old American system, will die out. Property ownership will take second place to community survial for all, and a sense of civility and caring for others never seen before in the unregulated vulture capitalist corporate ruled land will surface again as was once found in the decency of European village life. Mother Nature will re-take her position and the rule of the day will be green.

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Pamela Drake Apr 15 2009 at 7:03 PM

and we've got miles (hundreds of miles) of terrible, grey, metal barriers along the highways....what would it take to do something like this? It feels easier and much better to maintain. Cmon city officials, think big!