Morning File: Chilling out, big time
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That toddlin' green-roof town
It seems a good time to pose the question: How do you air-condition a city? One useful step is to put gardens on the roofs of big buildings.
Six years ago, Mayor Richard Daley did just that on Chicago's City Hall, with some 150 plant species, a small apiary and two trees. Today, Chicago is the green-roof capital of North America, with more than 200 of them transforming acres of tar into greenery, in the hope that rooftop gardens might cool and clean the air and help with storm drainage. Among the do-gooders with green roofs are an Apple store, a Target, a McDonald's and a soon-to-open Wal-Mart.
Chicago's green-roof push, The Christian Science Monitor reports, is part of a larger plan that includes adding hundreds of thousands of trees, increasing energy efficiency and replacing some traffic lanes with planted medians. The idea is to bring back some of the natural stuff displaced by buildings and pavement.
Will it make a difference? Sadhu Johnston, Chicago's environment commissioner, told the Monitor: "It's like turning off the water when you brush your teeth. Every building that does it this way has an effect."
Yes, but is it really air-conditioning?
Roof space accounts for 15 to 35 percent of a city's total area, says Steve Peck, executive director of Green Roofs for Healthy Cities. "What you have is a bunch of roofs that are like hot plates heating up cities in the summertime. With a green roof you actually turn that hot plate into an air conditioner."
Green roofs, first championed in Germany, are relatively common in Europe. The United States has only a fraction of the green roof space Germany has, but an April study found that our rooftop garden acreage grew 80 percent last year.
"Green roofs should be treated as necessary infrastructure for a city," Mr. Peck told the Associated Press. "Like sewers and streets." Advocates say subsidies or other incentives are essential. But not in sweltering Tokyo. Green roofs are mandatory there on all buildings over a minimum size.
Washington, Atlanta and Portland, Ore., are developing reputations as green-roof cities. One of the largest green roof expanses in the world sits atop the Ford Motor Co.'s River Rouge Plant in Dearborn, Mich.
The drawbacks? It's often twice as expensive to install a green roof, though it can last twice as long, and there are energy savings. And some buildings -- your house, for example -- aren't designed for the additional load.
China the green giant?
New York architect Steven Holl has designed many green-roof projects, but the demand is greatest at his Beijing office. One of his projects there is a self-contained city of linked vertical buildings, includes hundreds of apartments as well as stores and schools, and every roof is green. Storm water collected on rooftops will help feed a self-sustaining water system to protect against shortages. "They want it and they're willing to pay for it," Mr. Holl told the AP.
China has launched a nationwide drive to make energy-saving buildings that help ease fuel shortages and reduce greenhouse gases. The country has also signed an agreement with the United Nations to promote environmentally friendly practices in staging the 2008 Beijing Olympics.
'Go get some basil from the roof'
The Fairmont Royal York in Toronto has Canada's largest urban hotel herb garden on its roof. It's a lush 4,000-square-yard oasis of lavender, basil, thyme, tomatoes and zucchini.
The garden was planted in 1998 and is tended by the hotel's culinary team, yielding fresh produce daily for the hotel dining rooms. The Royal York wants to get experts from the Toronto Botanical Society to offer advice on what else it can grow on high.
Rooftop gardening is catching on in Canada. "Space on the ground is at a premium, and there are a lot of environmental benefits from green roofs," Laura Berman, coordinator of the Toronto Community Gardening Network told Canadian Press this week.
Roof gardens are an added benefit for people in apartments and condominiums. The cooling effect minimizes the cost of heating and cooling -- talk about green, as in money -- and esthetically a roof garden is a nice thing to have. An Environment Canada study found a 25 percent reduction in summer cooling needs, and a 26 percent decrease in winter heat losses with a green roof.
First Published August 4, 2006 12:00 am
