A section of the Central Park green wall

Green wall advocates have hit back at an attack from a leading architect on the value of green walls, citing energy savings and biodiversity benefits.

Green walls have come under fire with the national president of the Australian Institute of Architects, Richard Kirk, questioning their sustainability.

Green walls, or vertical gardens, have taken off in Australia, with many new developments now including them as a key marketing feature.

Mr Kirk, however, told The Australian newspaper on Thursday that they may become eyesores in the future.

“It will be interesting to see how well these green walls will last and stand the test of time,” he said.

While Mr Kirk said internal green walls had functional benefits in terms of air purification and aesthetics, he seemed to question the functional benefits of external “vertical gardens”.

“Certainly, introducing landscaping inside a building has a functional purpose in that it cleans the air and provides a visual relief in internal spaces,” he said.

“But where it’s just placed on the outside of a building, just to conceal a car park, it’s not a responsible use of how to make a city more green.”

The statement has caused upset among green wall advocates, who say there are many benefits to external green walls that have been ignored.

The One Central Park green wall was used to illustrate The Australian’s article, and is the tallest in the world.

Jock Gammon, founder of Junglefy, the company responsible for maintenance of the One Central Park green wall, told The Fifth Estate some comments in the article were “shortsighted” and failed to accurately depict the benefits of the technology.

Green walls, he said, provided a number of benefits aside from aesthetic value, and were key to greening efforts in city areas that did not have space for additional parkland, and where development was increasingly taking up that space.

He said currently unreleased research by Arup found heat load reduction in the order of 35 per cent attributable to the greenery’s cooling effects at One Central Park. Deployed more widely, he said there would be compound benefits due to a reduction in the urban heat island effect.

Increased biodiversity was another important factor. The Central Park green wall was now home to frogs, wasps, bees and even a family of peregrine falcons that “wouldn’t be there if there wasn’t the biodiversity, food sources and plants”.

“The bigger, forward thinking developers are looking beyond pure numbers and giving value to harder to value areas like biophilia and biodiversity,” Mr Gammon said.

For Central Park, even harder to measure is the value the green wall has had in making the development an icon.

“No one could have predicted how iconic this building would become, and certainly the vertical garden is a big part of the story,” Frasers Property Australia’s general manager for sustainability Paolo Bevilacqua told the Property Council last year.

He also listed benefits including increased worker productivity, plants as carbon sinks, minimising water runoff, improved air quality and increasing retail spend.

“How many other sustainability initiatives deliver as many co-benefits?”

National president of the Australian Institute of Landscape Architects Linda Corkery also noted a number of “economic, social, health and wellbeing benefits” from green walls.

“I absolutely agree with Richard Kirk that cities must continue to improve existing urban green space and parklands, and look for every opportunity to create more open space for city residents and visitors,” she said.

“However, there aren’t many developers who are likely to do this unless their development approval conditions require it. Wherever we have an opportunity to bring more green, more landscape into the city, we should be ensuring that happens. With increased development density, we must look for ways to continually renew urban ecological systems, and create more beautiful and liveable spaces.”

Is maintenance an issue?

Mr Kirk’s critique also took issue with the high maintenance costs of such green wall installations.

“Australia doesn’t have a low-cost labour market, and vertical gardens are very labour intensive,” he said.

“You don’t just set and forget.”

Horticulturalist Patrick Honan in 2015 estimated that it would cost almost $700,000 a year to maintain One Central Park’s green wall with its six full-time horticultural staff.

“Such a comparatively high level of input just for the sake of maintenance cannot be considered sustainable, as it is consuming resources like labour, money and fuel at a rate that is astoundingly high,” he said.

He also called out the water, energy and material use necessary for such a green wall, concluding that marketing such a system as sustainable was “almost offensive”.

Mr Gammon, while not able to reveal the actual maintenance costs, said the estimates were inflated.

He also said the costs would not be too dissimilar to maintaining parkland.

“Is it a bad thing that we have people maintaining or looking after gardens? People looking after parklands?”

Mr Gammon said the costs for both installing and maintaining green walls were coming down. One Central Park, for example, uses building maintenance units designed for window cleaning, which are generally only used a few times a month.

“They haven’t been designed for daily maintenance,” he said.

But new technology is making maintenance an easier prospect.

“It’s like with any new technology; the ancillary technology required for maintenance is still catching up.”

Research into more robust species is also keeping costs down.

More research needed

Dr Paul Osmond, director of the Sustainable Built Environment Program at UNSW, said the value of green walls over their lifecycle was still an open question.

“It’s a really good question and an area we are looking into more and more these days,” he told The Fifth Estate.

“From a service life perspective – from design, installation, maintenance, replacement of plants, water systems and even decommissioning – no one has really explored that.”

He did however say there was sustainability value in pure aesthetics, which he said was part of social sustainability. This included the value of nature in terms of biophilic responses such as stress reduction, particularly in otherwise built up areas like Central Park, where there was relatively little other opportunity for greening.

“It is a big social, educational and health benefit.”

A spokesperson for Mr Kirk said he had been accurately quoted in The Australian‘s article.

What are your thoughts on green walls? Important urban greening solution? Or expensive green wash?

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  1. I love them. How not surprising that The Australian would turn its steely glare upon them! Sydney should build some of those sensational and gorgeous ecosystem towers like they have in Singapore!

  2. Great to see some very pertinent issues raised here on many aspects of vertical walls. Love walking past Central Park and appreciate the maintenance expended on its green wall.
    These walls could raise additional questions around fire risk if the greenery has combustibility characteristics either from poor maintenance (dead leaves) or poor plant selection/substitutions – most of these walls could exceed NCC requirements for an attachment (by dint of area) and therefore would need to demonstrate how the entire system as an ‘external wall’ meets the required fire rating.

    1. While dead foliage can certainly burn, the greater fire risk with some VG systems comes from the PET plastic microfibers that constitute the synthetic felt that the reticulations run down to feed the roots – this is highly combustible and produces toxic fumes and as the layer often has an air gap behind it, which can act as a chimney the potential for a serious fire is high. We contributed to the guideline by the Tall Building Council who recommend breaking the surface area with “fire breaks”. Some countries now require breaks in the surface area to reduce the risk. The Tillandsia plants (air plants) we work with only use stainless steel for support and require no watering system so the risk of fire is minimal.

  3. Whilst some of the points made in the article are logical, we are still well short of quantifying all of the ecosystem services provided by green walls, and every time we study a new aspect, the outcomes are better than we expected.

    This is not yet an advanced science. As it stands, we have empirical evidence for the psychological / aesthetic aspects, building cooling and biodiversity, and good pilot data for outdoor air pollution mitigation and water treatment. With the foresight demonstrated by some in the industry side of green wall technology (Mr Gammon being a prime example), we in the research sector are being provided with the direction so as to accurately identify the key aspects of green wall that need to be studied, developed and improved. If you want to reduce chemical run off or maintenance costs, or reduce building HVAC use, or work out which plants work best in a given application, fund a research project or engage the horticultural industry, and we will find the answer

    The urban environmental criteria that may be affected by green walls are of vast and of growing importance. It would be wrong to curtail this technology and return cities to plain concrete walls because of concerns over such things as maintenance costs.

  4. If you want to read a critical paper on vertical gardens which also outlines how it can be done a super sustainable manner – read this paper we wrote for the Tall Building Council — https://lloydgodman.net/Cv/Press/TBUH1.pdf

    We also wrote a similar paper for the Green Building Council

    Issues that have come to light since we wrote the papers are; the fire risk from synthetic felt and pathogens build up in the reticulation system – We have now had experimental Tillandsia species at level 92 on Eureka Tower with no soil or watering system and importantly no maintenance for three and a half years!

    A map of the sites with the Tillandsia experiments can be found here https://lloydgodman.net/suspend/swarm/map.html

  5. A few of the assumptions here lie in comparing all greenlife technologies and applications as a single entity. Bonsai are not cheap potted colour, farms are not parkland, botanic gardens are not remnant habitat, vertical gardens are not vegetable patches and roof gardens are not green facades. There is a tendency to, erroneously, consider remnant, natural, habitat as low to no maintenance, whilst comparing the functionalities inherent to botanical gardens with parkland (for example). This error extends to comparing maintenance requirements.
    We will not extract the benefit and functionality inherent to botanic gardens or farms (for example) if we assume maintenance input requirements for either should be similar. Compare wetland water treatment vs. bioretention pools vs. roof gardens vs. urban farms vs. urban parkland.

    Vertical garden technologies have evolved in response to urban stresses and challenges. There are a plethora technological variations on the market, each exploring options and suitabilities, each of which will be tested/included/excluded by marketplace pressures, in time.
    Hydroponic and/or soil-based systems are not simply better or worse than alternative technologies as each configuration and application offers pro’s and con’s, pending how they are adapted/adjusted and appropriately managed. One cannot expect a racing car to cost the same and require the same maintenance as a bicycle or a bus.

    We can also not expect a water treatment system, bonsai, aquaponic farm, hydroponic system or remnant habitats to be maintained by-, and at the same cost of-, unqualified or unskilled labour.

    The fact that vertical gardens are shifting to address such a diverse range of urban challenges, illustrates how needed they are and how peripheral or allied fields (architecture, urban planning, city design, engineering, urban parkland, etc.) are currently insufficient and struggling, to solve these contemporary issues entirely.

    Consider the following functionalities vertical gardens are currently addressing and reflect on whether any one particular system can achieve everything simultaneously or if our criticisms of these urban greening technologies are well informed yet or not:
    VOC reduction (new and old buildings)
    CO2/O2 regulation and carbon sequestration (indoor and outdoor applications)
    Grey/Black water filtering/processing (in lieu of alternative, new and retrofitted, water treatment technologies -how much flushed water ends in stormwater, which should be reused in urban greening)
    Urban greening/Biophilicity (benefits to both host buildings and surrounding buildings gaining, gratis, visual access)
    Aesthetic improvement/Increase property value (internal and external applications with benefits extending to surrounding properties with virtually no floor space loss)
    Habitat production (needs to be generally inaccessible/undisturbed within the urban sphere)
    Urban amenity improvement (visual amenity is valuable)
    Thermal insulation (internal and external benefits to surrounding properties)
    Acoustic insulation (internal and external benefits to surrounding properties)
    Reduce urban turbulence (benefit to all buildings down-wind -urban pollution funnelling)
    Extend life/functioning of old buildings (retrofitted vertical gardens)
    Reduce/solve sick building syndrome
    Improve hospital patient recovery & reduce post-surgery pain medication
    Reduce urban heat-island effect
    Urban food production, etc. etc.

    Vertical garden technologies are certainly evolving, in conjunction with the peripheral and supporting technologies and design professionals providing beneficial inputs into the technology and its application. Improvements will certainly increase rapidly if social and professional awareness and education are improved.

  6. My view is that despite the shortcomings, they are still a fantastic innovation, and genuinely worthwhile investment, along with green roofs. Australia needs to catch up with the game on this for betterment of the environmental sustainability, building comfort and air quality.

  7. I cannot see how this is organic and natural. Yet another brainwave of the human mechanical mindset?

  8. Green walls can play an important part in urban greening and urban cooling. However, they should complement, but never replace, developers contributions to improving multi functional public green space in urban hot spots – both public parkland and engineered spaces for shady, long-lived street trees.

  9. WOW! about time we have some common ground. I have been preaching this for years and we are one of the worlds premier manufacturers. In fact my key note in London addressed “What is your design purpose” The article does not mention the dangers of these types of hydroponic walls, something I have also been preaching, the waste water and chemicals are a hazard and known to cause cancer, yet they are allowed to drain into the combined waste and into the water table. I would accept an invite from Richard Kirk to discuss in further detail how to protect the public yet provide the benefits. Bravo.

  10. As an economic test of sustainability, if the green wall was treated as parkland in a development and handed over to the local council, would the residents and businesses in that council area see the cost of maintenance as a reasonable use of ratepayers money?
    It would be interesting to compare costs of maintaining a small city park to a external facade green wall development. There is undoubtedly a lot of community benefit from the green wall, just the destressing of people walking by is of significant value, but this could become negative if it was left to die off.

  11. The issue of the maintenance of any landscaping on structure (vertical or horizontal) is a key element of any consideration of its sustainability credentials. Landscaping on structure is certainly not “set and forget” – it is a long-term, ongoing commitment. But this should not be seen as a blanket argument against all landscaping on structure (walls, roof decks, balconies) per se – it just means that in each instance landscaping has to be well designed, with consideration of the financial, practical and social aspects of maintenance into the future. There’s nothing much more miserable than a view of a neglected, dead landscape, and there are plenty of examples of poorly planned and maintained landscapes on structure failing shortly after developers have left the project – but the answer to this is not to abandon all green walls and roof gardens.

    1. You can’t maintain if it is not done right in the first place. Too many “experts” with no old school experience, since all of that is not new. The experience of a gardener comes from patience – not through technology.