Planting vegetation on rooftops to insulate and beautify buildings is a centuries-old concept. But in the 1970s green roof technology in Germany became more ambitious. Today, modern green roofs are combined with other green technologies to improve drainage and air quality, lower energy costs and even grow food. From basic designs that simply cover a roof in grass to more elaborate designs that incorporate flowers, native plants, vegetables and trees, green roofs are becoming a larger part of green infrastructure overseas—and the industry is beginning to expand more in Australia, too.
In February the University of Melbourne and Lord Mayor Robert Doyle introduced Australia’s largest research project on green roofs. Lord Doyle noted that rooftops make up 17 percent of total land area in Melbourne. “Green roofs are a tremendous opportunity to achieve savings for building owners and create attractive, usable spaces for tenants and residents,” he said.
Matt Dillon has been president of Green Roofs Australasia since 2008. Today he answers eight questions on green roof technology.
1. If we were on top of a green roof, what would the roof look like?
It would no longer look like a roof but a landscape in the sky. Most green roofs are turf or groundcover because of the depth of soil used to reduce loading, however I’m doing a project in Darlinghurst at present which will be a verdant native garden with trees, large shrubs, vegetables, herbs, pathways and pond.
2. What are some of the environmental and social benefits of green roofs?
The benefits are uniform for any urban population, however the drivers for green roofs vary internationally. In Germany it was heat insulation during winter, in Chicago it was to improve storm water quality and in Linz it was to improve air quality.
The focus of late has been to reduce building emissions and the Urban Heat Island Effect, which makes Sydney inner areas approximately two degrees celsius hotter during summer. The more hard surface (concrete on roads, rooftops, pavements, building facades) the faster city temperatures will rise. And then comes the increase in air conditioning, increase in energy consumption, emissions and so on. It’s a cycle and it rises incrementally with each new hard surface. The more urban vegetation, the cooler the city, the less the emissions.
Other benefits include increased realty prices and desirability; provides amenity space previously unused; creates new habitat areas; filters storm water of heavy metals; plants sequest carbon, filter air & produce oxygen; reduces storm water runoff at peak flow times, which mitigates flood events and damage costs; fire retardant Australian plants can protect houses during bush-fires; food can be commercially grown on roof-tops and delivered locally—with minimal transport costs and less emissions.
Green roofs are a win-win scenario.
3. What would be the cost for a typical roof?
Depends on all the variables—plant specifications, soil depth, irrigation, engineering—it’s not prescriptive. However, it is a roof system and should be considered at the start of a project rather than at the end, which is wrong. It should also be considered for the long term savings in insulation, extra usable space, improving the longevity of the roof membrane from radiation, hail, et cetera. Government should subsidise anyone installing a green roof because of the subsequent benefits.
I think we are lethargic about our bountiful ecosystem services in this country because there is no value associated with our blue sky, clean air, landscapes, oceans… Yet if you mine that landscape, there is value in what you take out.
I prefer we value our ecosystem now rather than when it’s gone.
4. Which country is leading the way in green roofs?
Germany and Switzerland because they spend the most on research and have the best policy for giving incentives. They know the benefits, they have been installing them for 40 years commercially, and it’s part of their urban planning big picture for ‘Green Cities’.
If governments lead the way then commerce will follow.
5. How does Australia stack up?
I would like Government to speed up the transition from the Brown Economy and move into the Green Economy, however there is a lack of vision and courage which is linked to our four year term of power and a three tier administration between Federal, State & Local—just can’t be progressive.
6. What new industry developments excite you the most?
Growing food commercially in urban areas. The population is expanding too fast and we will require food being grown on and in buildings.
7. Can green roofs be applied to residential homes?
Any building with a suitable roof surface which is waterproof. Green roofs don’t create leaks in roofs. If the roof substrate is correct then there will not be leaks. We’ve grown green roofs on a slope of 45 degs.
8. What are some tips for people who may want to try some green roofing on their homes?
Start with the garage or the garden shed: support it, seal it, drain it, plant it, grow it.