Sourced from Forbes
With space at a premium, cities are exploring new ways to make better use of their rooftops.
Our cities have never been denser, taller, or busier than they are now, and with that, comes the constant battle for land. Whether you’re a city dweller, developer, transport planner, or farmer, you’re forced to compete for dwindling amounts of available space. And with two-thirds of the world’s population predicted to live in cities by 2050, the stress on urban infrastructure looks set to outpace even the most carefully-laid plans. But if we look at aerial images of any city center, we can quickly spot plenty of unused space – the rooftops. Speaking to Scientific American, Steven Peck from a non-profit called Green Roofs for Healthy Cities, describes the roofscapes of our cities as “the last urban frontier – (representing) 15 to 35 % of the total land area.”
So what can we use this precious resource for? In a growing number of high-density cities, some of it is dedicated to recreation – everything from bars and pools, to soccer pitches and running tracks can now be found atop skyscrapers. Others host smog-eating roof tiles or questionable wind turbines, while in China, a large shopping mall has 25 villas on its roof. But when a rooftop offers access to sunlight, there are two more obvious candidates for its use – agriculture and solar power.
Green roofs have been growing in popularity for more than a decade, and in some cases, growing in scale too – atop a convention center in Manhattan sits the city’s largest, covering an area of 89,000 m2. Usually comprised of planted beds, or carpet-like tiles that encouraged the growth of low profile vegetation, green roofs can provide a habitat for birds and insects in an otherwise hostile environment. They also act as thermal insulation for the building, and reduce storm water runoff that can otherwise cause havoc in urban sewers.
Green roofs come with the added benefit of mitigating the dreaded urban heat island effect, whereby, as a result of heat-absorbing materials like asphalt and concrete, cities can be several degrees warmer than the surrounding countryside. In contrast, trees and green spaces can absorb shortwave radiation, and use it to evaporate water from their leaves – a kind of ‘double cooling’ effect. There are countless studies that back up this idea. One of the most interesting came from researchers at the University of Georgia. In 2015, they showed not only that ‘green’ cities are cool cities, but that networks of small urban green spaces, such as parks, gardens and green roofs, were more effective at reducing a city’s temperature than a singular park of the equivalent size.