The concept of green roofs has been well established in Europe and North America for some time and is starting to be incorporated into many building designs in Australia.
We have been slow to take up the trend of creating green oases in the sky but recent research tells us that there are many reasons to adopt sky gardens, and that they are less to do with aesthetics, and more to do with sustainability and affordability.
Buildings consume at least 40 per cent of a city’s energy, produce more pollution than cars or industry and increase ambient temperatures by up to 10C more than surrounding rural areas.
Rooftop gardens act as thermal insulators and keep heat in during winter, and out during summer.
Green buildings with gardens that carpet rooftops and atriums of plants have proved so successful in cutting airconditioning and heating costs that they are being mandated by countries.
As cities have evolved and living greenery has been reduced, carbon dioxide emissions have increased.
Sky gardens improve air quality and also act as natural drainage systems. They also help to absorb noise pollution.
As the price of land becomes more prohibitive and space becomes a rare commodity in many urban environments, the concept of using rooftop gardens for urban agriculture holds appeal.
A project with Central Queensland University began some time ago in Brisbane and Rockhampton, using rooftop gardens to process restaurant food waste through worm farms, with the nutrients being used to grow fresh produce.
Green roofs we know
Ironically, while we have been slow to move, Parliament House in Canberra has probably one of the world’s earliest and most successful green roofs - constructed in 1988, the design of the green roof was not due to sustainability but a desire to preserve the shape of the hill into which it was built.
In Brisbane, one of the city’s newest projects, the Mosaic apartments proposed for Fortitude Valley, plans an abundance of green spaces, green walls and trellises, and a herb garden, all incorporated within an ecologically sustainable, urban park-like environment in the sky.
But Melbourne appears to be the leader in the quest to green its skyline, with its “Growing Up” project, launched in 2009, to encourage the greening of city roofs, which make up 17 per cent of the city land area.
In July this year the green roof at 131 Queen St, the first roof garden retrofitted to an existing commercial building in Melbourne, was unveiled. Previously a blank expanse of concrete, it is now an inviting recreational space of flowering plants growing alongside herbs, fruit trees and vegetables. Food from the garden is used by the tenants of the building.
