Why green walls are more than just a pretty facade

Green walls have captured our imaginations since the days of the Hanging Gardens of Babylon. But today’s high-tech vertical gardens are more than just a pretty facade.

In their most basic form, green walls are just buildings covered with vegetation – from ivy-draped castles to Roman loggias laden with grape vines. But modern green or living walls bring with them an array of unmatched benefits.

External green walls can reduce the urban heat island effect and enhance aesthetics. In warm climates, greenery can reduce the surface temperature of walls, and shading windows with plants can limit solar gains and with it the need for artificial cooling.

Internal green walls boost indoor air quality by acting as filters, cleaning the air of harmful chemicals, dialing down carbon dioxide levels and enhancing oxygen levels. Cleaner air has been found to improve the health and productivity of building occupants.

Australia currently boasts the world’s tallest green wall. At One Central Park in Sydney (pictured), a joint development between Frasers Property Australia and Sekisui House, a 120-metre vertical garden is enveloped by 35,000 plants. Designed by French botanist Patrick Blanc, the green walls – all 1,120 sqm – are fed hydroponically.

Frasers Property Australia’s general manager for sustainability, Paolo Bevilacqua, says the green wall is “truly integrated” into One Central Park’s concept, and changed the project team’s entire approach, from the facade design and structure, to access requirements and maintenance schedules. “It even flows down to how much people will pay for the strata levies,” he says.

The building, which has received a swag of international awards, has been featured in countless architectural magazines. “No one could have predicted how iconic this building would become, and certainly the vertical garden is a big part of the story,” Bevilacqua adds.

Bevilacqua says few other sustainability interventions offer as many co-benefits as green walls. He lists improvements to air quality, plants as carbon sinks, the psychological and productivity impacts on workers, increased retail spend and enhanced biodiversity. Bevilacqua says vertical walls often attract new bird species, reduce the urban heat island effect, minimise water runoff and improve building efficiency.

“When a green wall is a significant component of the building, the benefits are significant. How many other sustainability initiatives deliver as many co-benefits?” he asks.

Vertical gardens are also an untapped opportunity in the retail sector. The regeneration project at Melbourne’s Burwood Brickworks, for instance, will feature an urban farm with produce that can “grow quickly and we can harvest regularly”.

“If we are growing food, we can run cooking classes that attract people who may not otherwise visit the centre. While they are there, they’ll go to the supermarket and café, spending more and increasing their dwell time,” he says.

 

Greening the globe

Internationally, vertical gardens are gaining traction. Malaysian architect Ken Yeang is considered a pioneer of ‘bioclimatic’ skyscrapers. Among his buildings is the Solaris in Singapore, which boasts a 108 per cent ratio of landscape to site area. This was achieved by integrating a linear green ramp, which wraps and winds its way around the towers, providing residents with access to terraces and gardens along the way. Yeang calls his buildings ‘living systems’ and he carefully selects native species to meet biodiversity targets for these urban ecosystems.

Meanwhile, Italian architect Stefano Boeri proposes to build “forest cities” to combat pollution in China, and has designed a city in Shijiazhuang with towers covered in trees and other plants. This prototype follows Boeri’s vertical forest in Milan. Two residential towers host 900 trees and more than 20,000 plants from a wide range of shrubs and floral plants. On flat land, each green facade is equivalent to 7,000 sqm of forest.

In France, a 1-metre skyscraper in Toulouse’s CBD is underway. The twisting spiral will feature suspended gardens that change colour with the seasons. And once complete, Clearpoint Tower in Sri Lanka will rise up to 46 storeys, covering every inch of the external surface and shielding the glass behind from the blazing Sri Lankan sun.

 

Indoor plants pack a punch

The University of Technology Sydney has been studying the link between indoor plants and environmental quality for more than two decades. Research group leader Dr Fraser Torpy says the industry has come a long way since it started measuring the effects of a few pot plants in the corner of the office.

Recent advancements in technology have taken green walls from “something tokenistic to something genuinely effective,” Dr Torpy says.

Extensive research arrived at the calculation that “206 pot plants were needed to remove enough carbon dioxide from a large office to have a worthwhile impact on air quality. But we’ve found that five sqm of green wall with enough light will remove the same amount of carbon dioxide from the air.”

Dr Torpy has been working with green infrastructure specialist Junglefy to quantify the benefits of the next generation green wall system, called the Breathing Wall.

Tests undertaken by UTS on the Junglefy Breathing Wall has found it delivers some of the “highest photosynthetic carbon dioxide removal rates observed in research to date”, says Dr Torpy. Further, it removes VOCs at a rate 1.5 times faster than the equivalent volume of pot plants, along with large quantities of particulate matter, one of the most dangerous air pollutants in urban areas.

Lendlease’s new global headquarters at Barangaroo South features a six-metre high interior wall covered with more than 5,000 plants. The wall, installed by Junglefy, is activated using mechanical fans, which provide uniform airflow across plants and growing medium.

Junglefy’s managing director Jock Gammon says this process “supercharges” the bacteria and microbes found in the growing media to remove harmful pollutants like carbon dioxide, particulate matter and volatile organic compounds from the air.

“This active ventilation offers all the benefits of a traditional green wall or pot plants – reducing carbon dioxide levels, filtering out air pollutants, and cooling and humidifying indoor air, but at a much greater level of efficiency,” Gammon says.

While Dr Torpy says it is very difficult to objectively measure workplace productivity increases, the impact green walls have on air quality is irrefutable, and the benefits continue to grow.

“We were initially concerned that the potting mix would release fungal spores, but what we’ve found is that green walls actually remove fungal spores. There is actually less mould in the air. This was totally unexpected,” he explains.

Interior green walls also have significant implications for energy efficiency and carbon reduction strategies, Dr Torpy explains, as air-conditioning is driven by the levels of carbon dioxide in the air.

“Plants live on carbon dioxide” so the right number of plants can reduce the need for air-conditioning to flush carbon dioxide from the air.

Gammon says the trendline is pointing towards plants being “embedded” into the interior design of buildings. Advances in lighting help the plants to photosynthesise, while smart sensors can track when green walls aren’t getting enough natural light or nutrients.

This isn’t about “green bling” Gammon says. “It’s about efficiency and functionality.”

In the future, we can expect to see everything from motorways to carparks turning a tinge of green.