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Sprout it from the rooftops

Sprout it from the rooftops

Every city contains up to 32 percent of unused landscape in the form of roofspace. Currently, there is a global experiment underway which hopes to utilise the roofspace to create biodiverse spaces that can solve city problems naturally. Simon Todd sums up key findings from last week's Living Roofs for Sustainable Communities presentation in Auckland, which featured talks by Candian Nobel Peace Prize winner Dr. Brad Bass.

Asphalt black, tin-roof green, hinterland grey. These are colours of the hardscaped city—the overheated colourscape for where we live work and play. Try as I might to keep lush Waitakere green and deep Waitemata blue hues in mind, Auckland is no different from any other city. It heats up and becomes unbearable, it washes its storm water away quick as a flash. It keeps biodiversity knocking at its suburban doors.

It doesn’t have to be this way, of course. It can harness sunshine, rain water, flora and fauna to cool it, refresh it, clean it—to break up the hardscape pallet.

In last week’s Living Roofs for Sustainable Communities presentation in Auckland, Unitec Institute of Technology’s Renee Davis and Candian Nobel Peace Prize winner Dr. Brad Bass shared their research, inspiration and where-to-from-heres, in a bid to offer solutions for city woes via the wonders of living roofs. 

Every city contains up to 32 percent of unused landscape in the form of roofspace. Currently, there is a global experiment uderway which hopes to utilise the roofspace to create biodiverse spaces that can solve city problems naturally—from intercepting rain and curbing stormwater polluted beaches, to cooling the air above cities and reducing heat-related mortality.

Germany and Europe are leading the living roof way, helped by established legal frameworks, financial incentives and building legislation for future living roofing. New Zealand is a green shoot in the global living roofs project, but hampered by lack of local knowledge and suppliers, suspicion of benefits and high cost with perceived risks.

For now, we are indebted to Renee Davis and her team, who have created New Zealand’s only extensive indigenous roof on a commercial building, in Waitakere city. The long-term aim is to “provide a viable urban opportunity to establish a network of islands in the sky, vital areas of native biodiversity and protective areas for rare and endangered flora and fauna—embedding the New Zealand island conservation tradition into our urban landscapes.” 

The trial and error approach of Davis and her team is contributing to the global network of experimentation, and it is a very important part of the global process. The New Zealand project is in its early stages and further reading on can be found here.

Toronto is a beacon for Living Roofs in North America. Here, new mapping techniques are pinpointing industrial areas that could be green-roofed in order to maximise biodiversity, and all new commercial buildings must have a percentage of green-roof capabilities. During his presentation, Dr. Bass, of the Centre of Environment at the University of Toronto, sights the three Ss when asked what makes a successful living roof. They stand for ‘substrate’, ‘structure’ and ‘spiders’.

Arachnids like damp spaces, which leads him onto the surprising conflict between living-roofers and solar panel advocates. Yes, there is an environmental battle on our cities elevated horizontal spaces. Apparently, the guys trying to clad roofs in solar panels despise the living roof makers. No space for both they say. Not so, says Bass, bringing it back to the shadows and damp spots created by solar panels which can be integrated into living roofs, indeed creating spaces for them to web and flourish.

Bass’ findings indicate that there are high amounts of spontaneous colonisation on living roofs. Species will find their way onto the roof via the wind or birds. Invasive plants will not stick around. Clover should be encouraged to increase honey bee populations. Living roofs resemble fields, not—as perhaps the public might have in their eye—the forest. We are not talking trees, fruit and big vegetation here. And neither are the roofs just for biodiversity—they provide easy camouflage for unsightly air-conditioning units, and other ugly roof-top paraphernalia.

As for the future, while DIY kits for Joe Public are available, Bass admits the private business sector needs to be convinced of the for their commercial outlets before living roofs become more than pockets of experiment. A trial living roof at a Walmart store in the States resulted in a decrease in the temperature of a normal Walmart roof, with less aggressive fluctuation in temperatures. This could be harnessed via a membrane beneath the living roof’s substrate, to control air conditioning and subsequently reduce heating bills.

Other projects on the cards include integrated bio-filters to utilise the water captured by living roofs and at the Adlershof Research Centre, a “facade greening system” is used to cool the building down.

Bass is also monitoring living walls, where nitrate created by goldfish feed mosses. These absorb the obnoxious chemicals emitted by office furniture and PCS. Having done its dash, the moss dies and falls into the fish tank, gobbled up by the fish, all the while beautifying the wall and making people smile.

A recording of the Living Roofs for Sustainable Communities presentation will be available on the Living Roofs website next week.

Waitakere Central Civic Centre: Crane delivery of substrate

substrate unloaded on roof

green roof September 2006

green roof November 2007

Images: www.waitakere.govt.nz