Green roofs the go
The Burnley Green Roofs Project will determine the best plant species and soils to use on city roofs, demonstrate how green roofs can use storm water and reduce building energy use and showcase how beautiful and multi-functional green roofs can be.
The project includes a large demonstration roof consisting of 14 different green roof types made up of distinct planting zones, irrigation and growing treatments; a research roof, dedicated to quantifying the environmental benefits of green roofs and plant performance; and a biodiversity roof, comprising a range of habitat features to encourage and sustain local wildlife.
The project was led by Dr Nick Williams and Mr John Rayner from the University of Melbourne, and the roofs designed by multidisciplinary design practice HASSELL to enable small group teaching activities and demonstrate the variety of green roofs available to the building industry.
The research team at the Burnley campus was the first to develop an Australian research green roof in 2008, which, although significantly smaller revealed a 48% reduction in summer energy use.
Dr Williams, from the Melbourne School of Land and Environment said green roofs had a range of environmental benefits that could help adapt Australian cities to climate change, as well as social and economic benefits that could make denser cities more liveable and attractive.
"Cities suffer from the urban heat island effect which makes them up to four degrees warmer than surrounding areas. Green roofs can help overcome this by reflecting the sun's radiation and providing shade or evaporative cooling as well as dramatically reducing a building's energy costs, trapping dust and pollutants and dampening noise," Dr Williams said.
"Green roofs act as a sponge reducing storm water runoff and potential flooding while lowering local temperature through evaporative cooling.
"We also want to use the biodiversity roof to understand how city roofs can be used to provide habitat and act as ‘stepping stones' to link fragmented urban wildlife habitat. This roof includes local native plants, an intermittent stream and hollow logs for habitat."
Despite the many benefits of green roofs, and their popularity overseas, they are not common in Australia.
Lord Mayor Robert Doyle said: "We know that roof tops make up 17 per cent of the total land area in the city. Green roofs are a tremendous opportunity to achieve savings for building owners and create attractive, usable spaces for tenants and residents. It is clear to me that successful cities in the future will be the ones that adapt quickly to what people want. And today people want to live in the city because it offers opportunities but they also want openspaces, parks and a clean environment."
Mr Rayner from the Melbourne School of Land and Environment said the aim of the Burnley Green Roofs Project was to illustrate what is possible, from non-irrigated succulent beds to deeper, productive vegetable gardens.
"Green roofs are functional and beautiful spaces that can be built new or retrofitted to existing buildings. Planning and design are key components to successful green roofs and the Burnley Green Roofs are an example of this," he said.
"We wanted to display a range of plants that can be successfully grown, but many need a certain depth of growing medium. Given we can't use a heavy soil on a roof we developed lightweight growing media, together with foam building blocks to create raised beds.
"We also wanted to maximize the plants and vegetation on the roof while maintaining access, so there are shallow planted areas beneath grated metal walkways."
The design team from HASSELL helped provide inventive design solutions to assemble the roofs.
Many elements of the roof were pre-fabricated and test assembled off-site, then transported and reassembled on the rooftop - this represents an innovation in design, research and construction process, said Mr Stephen Tan from HASSELL.
Ongoing research and the design lessons from the Burnley Green Roofs will now be used to provide technical knowledge for architects, landscape designers and public policy makers to install green roofs in Australian cities.