A roofing answer to climate change

Last month in the Sydney Morning Herald, controversial property tycoon Harry Triguboff challenged Australian cities to have more buildings and fewer trees.

As any urban planner knows, parks and greenery in cities and towns are vital “lungs” for air purification. They are all restful to the burdened soul.

But if he’s serious, rather than despising Harry's penthouse-and-pavement sentiments, we should suggest that Harry has his cake and eats it too.

Green roof technology has been around for years. However, most Australian property developers (including Harry), architects, planners, horticulturalists and building owners are yet to capitalise on significant profit prospects posed by the aesthetic, environmental and fiscal benefits of putting gardens on our roofs.

Already, Europe has developed green roof technology to a high level of cost-efficiency and positive environmental impact, while North American municipal governments, especially in Toronto, Chicago and New York, are also discovering financial and environmental benefits from well-engineered rooftop gardens (New York's Rockefeller Centre is a landmark example).

With the threat of global warming, green roofs provide reduction of ambient temperatures in cities, caused by the “heat island effect” of buildings and roads. A study released early this year in Toronto showed that green roof technology can reap huge cost savings for building owners and the community.

A key finding was that an 8 per cent cover of green roofs over the city would reduce the city’s heat island effect by up to 2C.

Rapid urbanisation around the world has meant that heat island effects of cities are becoming significant contributors to global warming. Compared with nearby rural areas, a city’s ambient temperature can be from 6 to 10C warmer because of heat absorbed and then released from roadways and buildings.

Cr Joe Pantalone, Deputy Mayor of the City of Toronto, said the study of the benefits of green roofs to Toronto also included direct energy savings of C$12 million a year in buildings from reduced cooling demand in summer.

Would a saving of this magnitude attract developers like Harry Trugiboff?

Cr Pantalone said savings also included indirect city-savings at peak load demand of C$80 million a year. Plus it meant reduced levels of carbon dioxide, nitrous oxide, ozone and PM10 particulates and sulphur dioxide from reduction of heat island effects and the trapping of gases and particulates by plants grown on green roofs.

Importantly for Australia, it meant reduction of stormwater flows by 12 million cubic metres a year, so that existing drainage infrastructure can cope, and sewage overflow events were less frequent. This also makes good economic sense: Cr Pantalone said Toronto’s savings were C$79 million a year from reduced capital costs for storm-water management, erosion control and sewer overflows.

Cr Pantalone said the City of Toronto was now encouraging the built-environment industry, especially building owners, to design and implement green roofs. The City of Toronto was now planning green roof retrofits on many of the city-owned buildings - especially because such retrofits could often be done within existing maintenance budgets, he said.

Other North American municipal governments, especially in Chicago and New York, are finding similar financial and environmental benefits from green roofs.

Rooftop gardens in Australian cities would generate significant air cleaning and water cleaning effects. Green roofs likewise enable slower runoff of rainfall at peak times, enabling drainage infrastructure to cope without massive and costly upgrades.

Key to all these benefits is, of course, the greenery itself. It must be drought-hardy, low-maintenance and attractive to the eye. Drought-hardy greenery means less costly rooftop maintenance, and Australia's hardy native vegetation is ideally suited for roof-top gardens.

Green roof technology is well advanced, and signifies important community, corporate and individual responses to the scary prospect of climate change. In Australia, we have a unique advantage. Our extraordinarily diverse and weather-hardy plant gene pool is ideally placed to help defeat runaway climate change effects.

Moreover, we have significant export opportunities in native plants with a capacity to range from plants sourced from Tasmania and Victoria's relatively cooler climates, to the dry arid zones of South Australia and Western Australia, to the tropics of Queensland and the Northern Territory.

Native flowering plants can support horticultural and roofscaping businesses in addition to providing a riot of delightful, restful colours across CBDs and sun-dried suburbia. Big payoffs also include reduced fossil fuel energy use, and more efficient water use - two points that should resonate across municipal, state and federal government levels.

But we shouldn't delay. Already the northern hemisphere advance guard is seeking out Australian native plants for their rooftops.

And already, Queensland is ahead of the rest of Australia. Queensland’s future green roof businesses can expect to produce healthy fresh food from recycled organic wastes. An urban organic waste management pilot project led by Central Queensland University (CQU) starts this month.

The pilot project will develop most strongly in the Brisbane-Ipswich urban corridor, and include up to two year’s research at Rockhampton. The aim is to recycle organic wastes into healthy fresh food within half a kilometre of where such wastes are generated.

The initiative is believed to be the first project of its kind. It is part of the expanding green roof movement now coming to Australia from Europe and North America.

Aside from the business benefits, community benefits of projects like these include reduction of methane pollution from landfill as organic wastes are diverted into recycling into fresh food.

They also provide fresh vegetables, fruits, herbs, fish and crustaceans around or above retail food stores, restaurants, cafes and food service facilities, and at rural schools and other isolated institutional organisations.

And they reduce urban air pollution by diesel transport - because fresh food is created where it is consumed.

Utilising rooftops for agriculture is one thing, but Australia should also take a good look at these exciting new uses and business prospects for our hardy coastal and inland plants before the Europeans and North Americans swipe our best.

So, how about it, Harry? Your apartment buildings deserve green roofs to save you loads of money - and to avoid the need to go to Katoomba to escape the heat and view the greenery!