TRENDY ROOFTOPS

If buildings suddenly appeared out of the ground like mushrooms, the rooftops of these high-rise buildings would be covered with a layer of soil and plants. Wouldn’t it be a grand occasion?

The urban roofscape is a little like hell with lifeless surfaces. However, Vancouver Public Library at Library Square is not like that. This 20,000-square-foot garden was created in 1995 by up-and-coming landscape architect Cornelia H. Oberlander.

Living roofs aren’t new, but in recent decades, architects, builders and city planners all across the planet have begun turning to green roofs not for creating residential areas, but for their practicality. Technology is only partly the reason. Waterproof material that covers the roof now makes it easier to design green-roof systems that allow drainage and provides irrigation. In some places, such as Portland, Oregon, builders are encouraged to use living roofs by fee reductions and other incentives. Researchers such as Maureen Connelly, who runs a green-roof lab at the British Columbia Institute of Technology, are studying the practical benefits green roofs offer and how they increase energy efficiency.

Another factor driving the spread of green roofs is our changing idea of the city. It’s no longer wise to think of the city as the antithesis of nature. Finding ways to naturalise cities will make them more liveable, and not only for humans.

During the summer, daytime temperatures on conventional asphalt rooftops can be almost unbelievably high, peaking above 150°F and contributing to the overall urban heat-island effect—the tendency of cities to be warmer than the surrounding region. On green roofs the soil mixture and vegetation act as insulation, and temperatures fluctuate only mildly—hardly more than they would in a park or garden—reducing heating and cooling costs in the buildings below them by as much as 20 per cent. When rain falls on a conventional roof, a living roof works the way a meadow does, absorbing water, filtering it, slowing it down, even storing some of it for later use. Above all, living roofs are stunning habitable areas. They recapture species which cannot continue living in cities. The solution fostered by Dusty Gedge, a British wildlife consultant and a driving force behind green roofs in the United Kingdom, is to create living rooftop habitat out of the same rubble.

Proponents of living roofs argue that they have met most of the technical challenges involved. While the average cost of installing a green roof can run two or three times more than a conventional roof, it’s likely to be cheaper in the long run, thanks largely to energy savings. Vegetation also shields the roof from ultraviolet radiation, extending its life.

Think of the millions of acres of unnatural rooftops around the globe. And now imagine returning some of that enormous human footprint to nature—creating green spaces where there was once only asphalt and gravel. If a certain sum of human happiness is the by-product, who’s to complain?

Adapted from National Geographic Website.