Trendsurfing: Green roofs
By David Rowan
Break up the decking, uproot the organic herb patch - today's fashion-conscious gardener cares more about what's growing on the roof than in the bedding. In these environmentally anxious times, rooftop greenery is emerging as the latest way to save the planet, its supporters convinced that plants atop our homes and workplaces will purify the air and cut our energy use. We're not talking about a couple of potted begonias perching on the rafters. A hardcore "eco-roof" needs to be as intricately planned as anything by Gertrude Jekyll.
The idea is beguilingly simple. You'll remember from school that plants take in carbon dioxide and give out oxygen, while also conveniently mopping up a few atmospheric pollutants. But just think what an entire layer of vegetation would do if planted on a waterproof membrane just above the top floor. Whenever it rained, the plants would absorb much of the water that would otherwise run off and clog up the sewage network. They would also insulate the building in winter and cool it in summer - a natural temperature-maintenance system, advocates say, which can significantly lower energy use.
The idea is currently catching on fast among the more ecologically clued-in architects and local authorities. Although the concept has been popular in Germany since the Fifties - and in various forms probably dates back to ancient Mesopotamia - it is only in the past couple of years that local subsidies and environmental worries have made "green" roofs a serious option for developers.
You wouldn't know it from ground level, but eco-roofs are moving almost mainstream. Barclays has planted one at the top of its Canary Wharf headquarters in London; a few miles west, the Ethelred Estate, in Kennington, has been refurbished to green more than 43,000 sq ft of roof surface. Increasingly, local councils are enticing developers with generous grants or tax breaks. Chicago has installed a 150,000-plant green roof on its City Hall, the Ford Motor Company has built a ten-acre "living roof" on its Dearborn truck plant in Michigan, and in Portland, Oregon, a heavily subsidised "sustainability" initiative is encouraging the greening of dozens of city-centre apartment and office buildings.
The big question is whether the effort can deliver all that it promises. Proponents cite studies that credit green roofs with absorbing nearly half the water that would otherwise have drained away, while at the same time cutting summer rooftop temperatures by up to 30 per cent. One study, in Toronto, concluded that green-roof coverage could cut city temperatures by up to two degrees and minimise smog. That's all very well, critics say, but eco-roofs can add enormous weight to buildings not designed to support them, and maintenance bills must be added to the extra installation costs. There is also some dispute as to whether, as claimed, eco-roofs will typically double a roof's life.
None of this need concern the green-fingered trendsurfer. All you need know is that rooftop vegetation is officially hot, with its own showcase garden at the Chelsea Flower Show, and a recent call from Vanity Fair for its fashion-fixated readership to "get a green roof". Of course, the neighbours may grumble when your overhead leylandii start blocking out the light, but just tell them you're doing your bit for the planet.
(The Times Magazine, May 20 2006)
Break up the decking, uproot the organic herb patch - today's fashion-conscious gardener cares more about what's growing on the roof than in the bedding. In these environmentally anxious times, rooftop greenery is emerging as the latest way to save the planet, its supporters convinced that plants atop our homes and workplaces will purify the air and cut our energy use. We're not talking about a couple of potted begonias perching on the rafters. A hardcore "eco-roof" needs to be as intricately planned as anything by Gertrude Jekyll.
The idea is beguilingly simple. You'll remember from school that plants take in carbon dioxide and give out oxygen, while also conveniently mopping up a few atmospheric pollutants. But just think what an entire layer of vegetation would do if planted on a waterproof membrane just above the top floor. Whenever it rained, the plants would absorb much of the water that would otherwise run off and clog up the sewage network. They would also insulate the building in winter and cool it in summer - a natural temperature-maintenance system, advocates say, which can significantly lower energy use.
The idea is currently catching on fast among the more ecologically clued-in architects and local authorities. Although the concept has been popular in Germany since the Fifties - and in various forms probably dates back to ancient Mesopotamia - it is only in the past couple of years that local subsidies and environmental worries have made "green" roofs a serious option for developers.
You wouldn't know it from ground level, but eco-roofs are moving almost mainstream. Barclays has planted one at the top of its Canary Wharf headquarters in London; a few miles west, the Ethelred Estate, in Kennington, has been refurbished to green more than 43,000 sq ft of roof surface. Increasingly, local councils are enticing developers with generous grants or tax breaks. Chicago has installed a 150,000-plant green roof on its City Hall, the Ford Motor Company has built a ten-acre "living roof" on its Dearborn truck plant in Michigan, and in Portland, Oregon, a heavily subsidised "sustainability" initiative is encouraging the greening of dozens of city-centre apartment and office buildings.
The big question is whether the effort can deliver all that it promises. Proponents cite studies that credit green roofs with absorbing nearly half the water that would otherwise have drained away, while at the same time cutting summer rooftop temperatures by up to 30 per cent. One study, in Toronto, concluded that green-roof coverage could cut city temperatures by up to two degrees and minimise smog. That's all very well, critics say, but eco-roofs can add enormous weight to buildings not designed to support them, and maintenance bills must be added to the extra installation costs. There is also some dispute as to whether, as claimed, eco-roofs will typically double a roof's life.
None of this need concern the green-fingered trendsurfer. All you need know is that rooftop vegetation is officially hot, with its own showcase garden at the Chelsea Flower Show, and a recent call from Vanity Fair for its fashion-fixated readership to "get a green roof". Of course, the neighbours may grumble when your overhead leylandii start blocking out the light, but just tell them you're doing your bit for the planet.
(The Times Magazine, May 20 2006)
posted by David Rowan at Saturday, May 20, 2006
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