Garden Cities First published in Environ, Summer 2003, ©Reed Business Information Australia 2003

©Reed Business Information Australia

Rooftop greenery and facade gardens - both could become the norm in Australian cities if trends from Europe take off here, says Katrina Fox

Hanging gardens may not be confined only to Babylon, if the trend of greening the cities, also known as "biotecture" keeps growing. As our cities become denser and hotter, many architects are now taking a keen interest in developing ways of incorporating more greenery into our urban landscape.
Terry White, executive officer of the Central Victorian Greenhouse Alliance, says: "We are 20 years behind Europe in this endeavour but there is considerable interest in Australia to doing it. The major bottleneck is in terms of access to the sort of technological information that is needed by architects to develop this reliably, because although it is available, a lot is in French and German."

One of the ways of introducing greenery to the cities is the creation of roof gardens. There are two ways of doing this, known as intensive and extensive greening. "Intensive greening is where a conventional garden is transported to a roof," White explains. "This method is expensive because you need to bear the weight of the soil required for a garden of that type. Also you need to have access to mains water to sustain it in situations of stress at altitude where it's drying out all the time and suffers extreme temperatures."

Extensive greening, on the other hand, utilises shallow growing substrata and lightweight Australian adapted plants for rooftops. "So we're looking at coastal, mountain, and desert species - plants that have evolved to be resistant to extremes of heat and cold and parsimonious in their use of water," White says. "So they are mainly succulent and can retain moisture in their metabolism. These are low or no maintenance as they do not need to be watered."

In Europe, extensive greening is bounding along, according to White, especially Germany, where 50 per cent of cities require roof greening in the urban central business district and another 50 per cent provide incentives for roof greening. "What's driving that is stormwater control," White says. "An absorbent roof knocks the peak off the storm flow and therefore drops the size of the engineering underneath."

White argues that the design community and developers need to come up to speed on the issue of extensive greening and is calling for training institutions to make the European technological information available. "We need to get demonstration projects out there, which will start the ball rolling," he says. "There are intensive gardens at height in Australia, but we need to introduce extensive greening. In my own home I am developing an extensive roof greening demonstration based on cost effective techniques and a selection of indigenous species. I'll be trialling it through the summer to see if the plants that are flourishing now will continue to flourish over our summer."

Another proponent of the move to green the cities is Chris Johnson, New South Wales government architect and author of the book Greening Sydney, who argues that the benefits to the environment and health are enormous. "Firstly the dense cities in the world are suffering from what's called the urban heat island effect, which means they are getting hotter than the surrounding areas because there are more surfaces that absorb heat," he says. "In Singapore and Tokyo greenery must be incorporated within developments to help lower the heat build-up which the city is starting to get.

"Landscape is also good at cleaning air, and having plants in the city also helps manage water - instead of it running off concrete and going into drains, landscape acts as a sponge to slow down the run-off. Landscape also helps biodiversity, so we can keep birds, bees and butterflies operating through the city, which is important for balancing the environment. Finally, landscape helps reduce stress in people."

As well as encouraging roof gardens, Johnson is also pushing for garden apartments. "The concept behind these is to translate the idea of suburban house into a six-storey building so that you have large north facing terraces or balconies of around 35sqm which could be landscape with gardens and space to have outdoor activities. It should look like a series of individual houses put together so the identity of each unit is retained. Rainwater would need to be caught and recycled through the water storage system to avoid using the mains water system."

Another way of greening the city is the creation of aerial gardens. The Capita Centre in Sydney has aerial gardens on different floors of the building. "In Singapore, they encourage apartments to have aerial gardens," Johnson says. "It's not just on the roof or on a terrace or balcony, but up on say between the 15th and 18th floor you might have a three-storey atrium space which would be filled with gardens."
Vertical greening or façade gardening is another method of introducing greenery to a building. According to Peter Ho, principal architect at design company Boughouse, which produces and maintains vertical plantscape systems to cover the walls of buildings, "It is important to note that building facades constitute a significant percentage of the total surface area in the urban environment in comparison to that of the street or rooftop. Subsequently the function of widespread placement of façade gardens has significant potential to absorb urban air pollutants and to mediate the urban wind tunnel effect."

While modern building facades are generally not designed to incorporate gardens, there is a range of retrofit options that can be implemented, Ho says. Containerised façade gardens utilise support structures, such as stainless steel to hold the plants, ensuring direct plant contact with the building. In-ground façade gardens, where the plants are grown from ground level are the most cost effective solution and are generally low maintenance, according to Ho. "The principal issue is the limits to upward growth for the species. Careful selection of woody and long-lived species will enable the planting to reach three or four storeys in height," he explains.

To reach a situation where greening the cities becomes the norm, Johnson believes that both mandatory and incentive approaches are useful. "What would be good is for development applications to require a certain amount of landscape," he says. But one of the obstacles to overcome is resistance by some architects to greenery. "There has been a divide between architects and landscape architects," Johnson explains. "Architects are often more interested in the sculptural qualities of a building they produce than to how well it fits into nature. "The Conservatorium of Music, which I designed, is covered by gardens and landscape terraces, but some people will say it should be a building that's not hidden by landscape. Some architects think it's a bit of a cop-out to blend a building in with nature, but I think it's a better way of doing things. In Europe there's a much greater understanding of this. "It's a new approach to nature - the incorporation of landscape and building into an integrated and organic approach."

Environ magazine goes out to architects and building designers with a specific focus on sustainable architecture and building design. This article is the copyright of the publisher, Reed Business Information and appears here with their permission. For more information on the magazine, visit Reed's website at http://www.reedbusiness.com.au