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Green Smart Magazine : 2009_new
'However, in regard to climate change and global warming, we're all in a similar situation in terms of trying to reduce our carbon footprint. ' Green roofs can be quite complex (see box on page 11) and are generally more effective in large-scale urban environments. There they can have a greater impact on reducing the so-called urban heat island effect of major cities where temperatures are often higher, caused in part by the retention and radiation of heat from materials used in these areas. However, adding a green wall is relatively easy and Sidonie says they are highly achievable for the average homeowner. 'There are very few limitations with green walls,' she says. 'As long as you understand your aspect (and therefore your plant species and selection) a green wall can go anywhere -- internally or externally and to any height because structurally they usually support themselves.' Green walls, also known as living walls or vertical gardens, can be used as feature walls or dividers in courtyards as well as for growing herbs and vegetables. The various systems generally require a lightweight structure to provide support for the plant roots and a means of storing water and nutrients essential for healthy growth. These structures can either be freestanding or attached to the wall using cables, trellises or frames. The three main green wall systems are: • planting into a fibrous material such as felt • using pots or planters arranged up the wall • ready-made modular panels that can include pre-grown plants or be planted after installation. HIA GreenSmart coordinator, Neil Sephton, says that external green walls can reduce your energy bills. 'Exterior green walls can insulate the building from the sun's heat and produce a cooling effect as water evaporates from the planting module and the plants give off water vapour,' he adds. 'Any reduction in the temperature of the building envelope will reduce energy consumed in cooling the home.' Improvements in air quality are also a benefit as shown by Sustainable Gardening Australia. 'Certain plants are known good absorbers of volatile organic compounds (VOCs), other undesirable chemicals and carbon dioxide. Under closed chamber tests, some plants can eliminate VOCs or reduce levels by up to 20 per cent in flow-through situations. ' With improvements in technology making it easier and more economical for people to include a green roof or wall, along with increased energy efficiency requirements, their future seems likely to flourish. gs SUITABLE FOR COMMERCIAL AND RESIDENTIAL APPLICATIONS, GREEN ROOFS AND WALLS NOT ONLY LOOK GOOD BUT PROVIDE A RANGE OF BENEFITS 12 greensmart 9 greenroofs+walls green walls at a glance Green walls vary enormously but a typical vertical system comprises the following elements: • vegetation appropriate for either the indoors or outdoors • a modular panel system to contain the roots and the growing medium • an integrated drip irrigation system and controls • a catch basin to control water run-off • a structural support system. Some important design and structural considerations specific to green walls include: • protecting the structural support system's integrity • adequate waterproofing to avoid long-term damage • efficient drainage • a long-term, lightweight planting medium, usually synthetic, that won't deteriorate • irrigation and fertilisation for plant growth and sustainability • adaptation of the plantings to the environmental conditions • maintenance. Photos courtesy of Green Roofs Australia