Living walls look amazing, but their beauty is not just skin deep. In this article we look the evidence and research supporting the sustainability and environmental benefits of green walls. These include how living walls benefit people and society by helping to reduce pollution and nuisance; how they benefit buildings by moderating temperature and noise, reduce energy consumption; how they help companies by reducing bills and improving corporate image.
Living walls demonstrate your commitment to sustainability
Living walls are an excellent and very visual demonstration to customers, public, employees, shareholders and government of your brand’s commitment to the environment and sustainability. So many more people will see and benefit from the living wall on the front of your premises than will ever read your CSR report.
As part of its Plan A sustainability business strategy, UK retailer Marks and Spencer has been installing living walls on new stores and existing stores for a decade. The most noteworthy is the 300sqm of living walls at the MS flagship sustainable learning store at Cheshire Oaks lauched in 2015. The living wall, which uses both ANS and Jakob green wall systems, helped the store achieve a BREEAM Excellent rating, the industry recognised environmental assessment of buildings.
Other stores getting the living wall treatment have included the existing M&S store in Newcastle (also ANS), the new M&S store in Sevenoaks (Biotecture) and the M&S Simply Food stores at Slough, Heswall, Oswestry and Epping (Scotscape). With M&S expected to relaunch Plan A in early 2021, it will be interesting to see if living walls continue to have a starring role.
Living walls help reduce air pollution in cities
Each year in the UK, up to 11,000 deaths due to a heart attack or stroke are attributable to toxic air, with the danger that it could get much worse, according to the British Heart Foundation research (2020). Air pollution is a lethal combination of particulate matter (PM) – mostly soot and dust – and gases such as nitrogen dioxide (NO2), ozone (O3), sulphur dioxide (SO2) and carbon monoxide (CO).
Exhaust fumes from polluting vehicles are a major contributor of both PM and gaseous pollution in our cities. Pollution is particularly bad in city streets where buildings on either side of the street create what is known as ‘street canyons’ which trap pollution at street level.
Research by Pugh, MacKenzie, Whyatt and Hewitt (2012) shows that introducing green walls, along with green roofs and street trees can reduce the concentration of pollutants in street canyons by as much as 60% for PM and 40% for NO2. Meanwhile research by Arup (2016) found that green façades can result in local reductions in concentrations of particulate matter, by 10 to 20%.
Living walls make excellent screens to hide large structures and reduce noise
It is difficult to make some buildings e.g. car parks, shopping centres and warehouses things of beauty, but green walls and green façades (climber walls) can help minimise the visual impact. Green walls can also help mitigate potential nuisance from noise from crowds or vehicles or pollution from buildings or vehicles.
One of the best examples of green wall screening is the huge network of double-sided green walls, measuring 1,400sqm, at London’s Westfield Shopping Centre delivered by Pritchard & Pritchard, working with Urban Planters, using a GSky system.
This lovely wall – featuring Ferns, Carex, Bergenia, Hebe, Hellebore, Pittosporum, Rosemary, Nepeta, Euphorbia, Ajuga and Liriope – shields Europe’s largest retail destination, with 477 shops and 31.2 million annual visits, from its residential neighbours.
Living walls help reduce heating and cooling bills
Buildings lose temperature through the walls and roof during the winter and gain temperature through the walls and roof in the summer. Green walls or façades and roofs help insulate the building reducing the costs associated with heating and cooling.
According to the London Living Roofs and Walls Technical Report (2008) the shade provided by living walls to buildings can reduce temperature fluctuations at the wall surface from between 10°C and 60°C to between 5°C and 30°C. Additionally green walls and façades create a zone of still air adjacent to the wall can reduce convection at the wall surface by up to 75 per cent and heating demand by up to 25 per cent.
This is demonstrated very well using thermal imaging. Green Wall on the Go pictured here was a mobile demonstration by the State Government of Victoria used to prove the benefits of green walls to local residents.
Living walls help combat the urban heat island effect
It is hotter in cities than in the countryside – in the most populous cities it can be 12°C warmer, particularly at the end of the day. This is known as the urban heat island (UHI) effect caused by buildings, roads, paving and roofs absorbing and trapping heat. Meanwhile in countryside plants help shade the ground, while also providing cooling through evaporation and transpiration. This is explained well by this diagram from Skeptical Science.
Green walls and roofs mimic the vegetative coverage of countryside, helping to shade and cool buildings from the sun, and resulting in buildings absorbing less heat and contributing less to the local UHI.
The Cities Alive: Green Building Envelope report by Arup, 2016, studied the impact of living walls and roofs in cities around the world. It found that green wall / façades effectively remove 50% of solar radiation into a building. This can help reduce UHI by up to 10°C in the most dense urban city centres like Hong Kong or Melbourne.
Living walls reduce noise pollution
Living walls are proven to be more effective at dampening sound from outside the building, such as traffic, crowds and construction, than most common building materials. A 2014 study by Azkorra et al found that green walls can absorb 40% of sound and will reduce sound levels by 15 decibels.
The study compared the acoustic dampening of a green wall to brick, concrete, plaster, wood, glass, marble and fiberglass. The only material that was more effective than living walls was 25mm fiberglass board (which is commonly used for soundproofing). The results of the study are shown in the graph.
Living walls are excellent for biodiversity
Living walls improve diversity by providing a food source for invertebrates (which are eaten by birds) and providing breeding and nesting habitat for invertebrates, birds, and possibly bats.
A fascinating 2014 PHD thesis by Caroline Chiquet studied the biodiversity present in 22 green walls and 29 green façades (climber walls) in the UK, found that birds were present in residential areas with green walls than similar areas without green walls.
In total, Chiquet found nine species of birds, 13 species of snails, 33 species of spiders and over 2600 morphospecies across façades and walls. But there was considerable difference in species mix between green façades and living walls, leading Chiquet to conclude that the two should be considered as different and important ecosystems. Chiquet found that the living wall system had far less influence over the abundance of species, than the plant diversity, plant density and the age of the wall.
The biodiverse wall pictured is designed and planted by Scotscape, with installation services from Pritchard & Pritchard. The wall includes bird boxes and 73 species of bird and pollinator-friendly plants and plant species that are particularly good at capturing particulate matter.
Urban greening helps inflate property value
The abundant planting that adorns at Milan’s Bosco Verticale – which means ‘vertical forest’ in Italian – has helped this masterpiece from architects Barreca and Giovanni La Varra become the poster child for sustainable architectural design. It has also helped the apartments become very hot property with well-to-do purchasers and investors – and some of the expensive real estate in Milan, Italy.
International Highrise Award awarded Bosco Verticale the “most beautiful and innovative high rise in the world.” It has spawned look-a-likes in Shanghai, Beijing, Switzerland, Paris, the Netherlands, and the world’s first Forest City in China’s Liuzhou.
The penthouse flat at Bosco Verticale went on the market in late 2020 for $17.5 million according to Forbes.