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Why Green Roofs and Walls are the Next Big Thing


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Landscaping is no longer just a pretty little extra around a building; it is becoming an integral part of it.

The green roofs and green walls trend is gathering momentum, driven by a combination of sustainability goals, design ideals and, in some cases, explicit policies.

The City of Sydney adopted Australia’s first green roofs and walls policy in April 2014. Since then, rooftop vegetation and vertical gardens have been sprouting across the inner city. They include One Central Park’s dramatic Patrick Blanc living facade, a green wall at Google HQ, a green roof on NSW Parliament, and numerous green walls and green roofs accessible to the public at car parks, hotels, shops, and public buildings.

Since April 2014, rooftop vegetation and vertical gardens have been sprouting across Sydney .

Since Sydney broke ground on the concept, other councils have followed suit. Brisbane City Council has made urban greening a part of its sustainability strategy, City of Adelaide has been offering grants to assist building owners in retrofitting green walls, and City of Melbourne values green roofs and green walls as part of its broader Urban Forest strategy.

The motivations behind the rise of the green wall and green roof include mitigating the urban heat island effect and future-proofing cities against rising temperatures due to climate change. There are also advantages in terms of improving air quality, enhancing people’s wellbeing through exposure to green space and natural elements, and helping improve the quality of stormwater runoff.

Green roofs have additional advantages of providing improved thermal insulation for a building and reducing the amount of stormwater run-off. Green walls, on the other hand, can be used strategically to improve a building’s acoustic performance and to absorb pollutants. These include airborne particulates emitted by vehicles, volatile organic compounds emitted by furnishings and finishes, as well as dust generated by construction and other activities.

The design guidelines for the Melbourne Metro project, for example, suggest the use of temporary green walls around station construction sites to reduce noise impacts, manage dust, and add amenity for both workers and the surrounding community.

A number of approaches and technologies have evolved to actually create urban greening. 

A number of approaches and technologies have evolved to actually create urban greening. They include simple soil-based planters at ground level with trellises of tensioned steel cables to support plants as they grow, such as those supplied and installed by Ronstan International at the QEII Courts of Law in Brisbane.

One Central Park’s living facade combines tensile cables, hydroponic planters, and a high-tech monitoring system that measures and maintains water and nutrient levels.

Green roof projects may comprise a system of planters and raised beds, as is frequently seen on apartment and hotel developments, or a full-scale sky park with trees, lawn and productive gardens like the Upper West Side Sky Park and Gardens in inner-Melbourne.

The project won designer, Nicholas Rivett and developer Far East Consortium the inaugural Australian Institute of Horticulture Green Space Urban Award in October 2017.

The park and gardens include 12,014 plants across 232 species in a growing medium comprising scoria, sand, coir, bark and wood chips to a depth of between 400mm and 2.5m. 

Lead contractor Brookfield Multiplex had to manage the craning in of approximately 2,500m3 of the mix to the site’s fifth and sixth floor locations.

The green installation is expected to sequester 2.6 tonnes of carbon dioxide annually, and retain around 400,000 litres of water following a 100mm rain event. Re-use of captured rainwater for irrigation is expected to save up to five million litres of potable water every year.

Re-use of captured rainwater for irrigation is expected to save up to five million litres of potable water every year. 

Director of Australian Ecosystems and Biofilta Stormwater Solutions, Brendan Condon, tells Jobsite that greening urban rooftops, carparks and other under-utilised spaces can also deliver another important positive – helping our cities feed themselves.

One of the major challenges with many rooftop systems, he says, is ensuring that both waterproofing and the roof engineering design can cope with the water and the additional weight involved.

What is more, many systems, such as hydroponic ones, require additional electrical systems and monitoring technologies. However, Biofilta has developed an alternative solution – modular Food Cubes. They can be installed anywhere to create an urban farm. An entire installation can be completed in a fortnight, he says, and the system requires no supporting technology or electrical infrastructure. The way the Cubes are designed also means there is no need for additional waterproofing.

The Food Cubes are an advanced wicking bed that collects and retains rainwater, and aerates the roots of the plants, which grow in a soil-based medium. Hoops and netting protect the plants from pests and excessive UV radiation.

Condon says the system can be part of transforming cities into water catchments and productive urban farms. It can also help convert current waste streams such as organic waste and stormwater into productive resources, with food waste used as compost for the growing plants and stormwater collected and used for watering.

The company is already working on projects around the world where food security is an issue and in slums, where adding food production improves both lives and general liveability.

There is a need for Australian cities to have this kind of infrastructure too, he says, adding: “Cities need to be more closed-loop and food secure. There are all these spaces available for urban farming if we have clever food growing architecture.”

Condon says there is “huge interest” at the community level in producing “super-local food.” 

Condon says there is “huge interest” at the community level in producing “super-local food.” 

He points to Paris as a city that is leading the way in this space, with local government policies deliberately encouraging the use of roof spaces for productive urban agriculture.

“Around the world there is some good acceleration in this space.”

He says there are multiple benefits. For one thing, people “love green space.” There are positives too in terms of people engaging socially through the gardens, exercising more and having better nutrition. Moreover, Research has shown urban farming in the form of community gardens improves neighbouring property values, he says.

Condon predicts that having buildings turned into thriving, productive, community-building places through installing food-growing urban greening will be the “next big thing” in the property sector.

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