All Trades Australia

MELBOURNE'S steel and concrete skyline will turn over a new leaf today with the unveiling of the first roof garden on an existing commercial building.

The new green roof has been fitted on to a 10-storey office block at 131 Queen Street, at a cost of about $250,000.

It is set to reduce the building's energy needs for summer cooling by more than 50 per cent, researchers at the University of Melbourne and the CSIRO say.

Previously a blank expanse of concrete, it is now an inviting recreational space. Hardy succulents and native flowering plants and grasses grow alongside a herb garden, lemon and olive trees and wisteria and passionfruit vines.

There area also has a built-in barbecue, a gazebo and a picket fence around the perimeter.

The food the garden produces will be available to the 20 small-business occupants, which include the Fo Guang Yuan Buddhist art gallery, the Lyceum Language Centre and Open Universities Australia.

The paving is made of permeable recycled glass that filters rainwater into the building's green roof system. There is also a small research space for the University of Melbourne's school of land and environment, which is studying the best plant and soil types for green roofs in Melbourne.

The university's Nick Williams said roof gardens could be an important tool in reducing the atmospheric heat generated by cities.

''We're very interested in green roofs for climate change adaptation, because they save building energy use and they can help cool the surrounding environment, so being able to retrofit them is very important [because] most of our building stock is not going to change,'' he said.

Green roofs are becoming common currency in new environmentally sustainable buildings in Australia, but are rare on existing stock.

The high cost and the threat of heavy soil damaging the building's structure are two of the biggest obstacles.

The roof came out of a collaboration between business, government, the green roof sector and scientific researchers, led by the Committee for Melbourne. Spokeswoman Tiffany Crawford said: ''We have a sea of grey concrete up there and we really wanted to capture people's imagination and point out that building owners aren't using all the building space they can,'' she said.