Living roofs help cool cities, capture stormwater run-off, insulate buildings and reduce their carbon footprint. They also dampen noise and provide green habitats for birds - and people - in the concrete jungle.
With more than half of the world’s population living in cities, advocates say the living roof’s moment has come.
The landscape architect and living roof expert Raphael Garcia, of the Californian architecture firm Rana Creek, who was to give a lecture at the University of NSW last night, told the Herald: ”The big thing we’re trying to do is to change how we view our cities. Now it is polarised - the urban environment is a place for people, or you go away from people and that’s a place of nature and a place of healing. We’re trying to integrate nature into our cities.”
His projects include an undulating green roof over Renzo Piano’s building for the California Academy of Sciences in San Francisco, ”healing gardens” on the roofs of hospitals and a 3.5-hectare garden over the Croton Water Treatment Plant in the Bronx.
One of Rana Creek’s most ambitious projects is a botanic garden on top of the new rail and bus hub in San Francisco, the Transbay Transit Centre, which will be six blocks long and about 30 metres off the ground in the middle of the city’s financial district. It will be the first roof garden to have redwood trees and its own wetlands to process greywater, and it will capture all stormwater to flush the building’s toilets.
”It’s more than just a green facade,” Mr Garcia said.
Waterproofing and ensuring structural loading capacity tend to be the largest costs in building a green roof, but in essence they are quite simple and may be retrofit to existing buildings, Mr Garcia said.
A root barrier, drainage mat and filter are minimum requirements before the soil can be laid.
Roofs are also being used for urban agriculture - China’s biggest cities have started cultivating rice on roofs - but Australia is lagging well behind the rest of the world in promoting them, the upfront costs turning developers off.
Matt Dillon, of the non-profit organisation Green Roofs Australia, which is sponsoring Mr Garcia’s visit to Sydney this week, said planning bodies should provide incentives to developers to include green roofs on their buildings, such as tax relief or floor space bonuses.
Mr Dillon said: ”For so long buildings have been responsible for high carbon emissions, now it’s about getting to carbon neutral and then beyond that, it needs to be restorative where the buildings start to give back to the environment as well. That’s the challenge.”
