Going to the rooftops to stop climate change

In the past few years solar panels and wind turbines have become familiar friends, comforting images that give us hope for a greener future. Featured in the media and in corporate advertising, these new technologies have replaced cute pandas as an icon of environmental correctness.

But how many people out there have heard of green roofs, which may be an equally powerful tool for dealing with climate change? Not many, I bet.

Why? Green roofs are often homely, not photogenic. They are made of plants, not zippy new technology. Most important, perhaps, it is hard for large corporations to make a profit installing green roofs – so they are not promoted or featured in glossy advertising.

Creating a green roof, or living roof, involves putting down soil and plants on top of buildings – apartment blocks, corporate headquarters, even private homes – a practice that has multiple benefits for the environment.

A green roof is wonderful insulation for the building below, keeping it cool in summer and vastly reducing energy needs. In cities, green roofs help absorb CO2 and have a cooling effect. They soak water from rains, taking pressure off drainage systems. They give local species – plants, birds and insects – a place to roost, preserving biodiversity.

“There are not many technologies that give you so many environmental benefits,” said Dusty Gedge, co-founder of LivingRoofs.org, a group that promotes and provides advice for green roof installation in London. “But a living roof is not a piece of hardware that you can just install; it’s an ongoing process. So architects and builders and consumers have a hard time dealing with it. It’s not like a solar panel.”

Ed Snodgrass owns Emory Knoll Farms in Maryland, the biggest nursery devoted exclusively to green roof plants in the United States. He said that green roofing was a difficult sell because it was hard for consumers to grasp and quantify the diverse benefits, and because it did not satisfy people’s desire for a quick solution.

“A solar panel fits into our need for problem solving: It increases capacity so you still get to have the SUV,” Snodgrass said. “But a green roof is a living, complex system.”

A handful of cities around the globe – like Linz, Austria; Potsdam, Germany, and Portland, Oregon – have promoted the planting of green roofs for more than a decade as a method to deal with excess rainwater runoff or simply to increase the green in the local environment.

More recently, cities from Toronto to London to New York are exploring them too, but now as a way to blunt the effects of global warming. They are considering implementing plans that would require large buildings or new buildings to be topped off with green roofs. Or giving tax breaks to builders and developers who create them.

These days, green roofs have some well-placed fans.

Green roofs “have a dramatic impact on energy use, greenhouse gas emission and parenthetically on the energy bills of every business and residence in all those buildings,” said Bill Clinton, the former U.S. president, in a recent speech in New York.

In fact, Clinton suggested, green roofs could be a powerful source of jobs as well. “You cannot outsource these jobs. Someone has to be standing on that roof. This is not data processing. You’ve got to actually be there.”

The fact that all green roofs are inherently local, however, also “makes it hard to develop an infrastructure,” Gedge of LivingRoofs.org acknowledges. “There is no powerful economic driving force – like the companies that sell wind turbines – to promote green roofing.”

“If you call a company with experience in Stuttgart and say I want one in the Philippines, it won’t work,” Snodgrass said. While his company ships to Oregon, it is only because no one is growing green-roof plants there yet. “It would be far better to have a local nursery,” he said.

While green roofs are relatively cheap to install, the building underneath must have a good seal and the garden needs to be maintained.

For cities, some of the benefits of green roofs are simple math. When the sun shines on a tar roof, the temperature can go up to 170 degrees Fahrenheit (76 degrees Celsius). That absorbed heat not only roasts the apartments below, but also releases heat into the air, creating a “heat island” effect, raising urban temperatures 7 to 10 degrees Fahrenheit compared with the surrounding suburbs.

“That created a huge stress on the air-conditioning load, which has led both Chicago and Atlanta to look into green roofs,” Snodgrass said.

When a roof is sealed, covered with a layer of dirt and planted, it does not serve as a heat sink.

Once installed, developers have found other unanticipated benefits. When the Four Seasons Hotel in Boston installed green roofing, it was initially for storm water management. But managers soon discovered that guests loved rooms overlooking the plants.

from http://www.iht.com/articles/2007/10/24/bloomberg/greencol25.php