The Vegetated Building Facades and their Contribution to Environmental Sustainability

buddhichathuranjelidesilva@gmail.com Abstract The number of people who are affected by urbanization has radically increased. However, the economic boom over the past decades has escalated the environmental problems. Among other solutions, environmentalists have proposed vertical greening, which refers to allowing vegetation to grow on the vertical surface of a building. With other sustainability-oriented strategies, vertical greening is thought to help resolve current environmental issues, as well as current health issues. It may prevent the cities from being unbearable during locked downs which impacts human’s mental health due to social distancing measures. Green walls are an option for cities for people to engage with Nature. Known for their pleasantness to the senses and earthy qualities, they boost human health and improve air quality. Plants can thrive on walls, making it a popular trend globally and also welcomes antidotes to stress and isolation. Plants which contain day-to-day supply of nutrition and anti-germ characters, could be incorporated with green walls. However, more knowledge is needed to reap the potential benefits from it. With the demand for sustainability, green walls are increasingly appearing on clients’ requirement lists but mostly as a visual and aesthetic representation of sustainability. This sensibility of clients, what architects provide, and what is eventually built, questions whether the current vertical gardens deliver the intended benefits. Are these walls environmentally-friendly or are they just being a trend that takes advantage of the concern for the environment and human fondness to certain measurements used to assess the above perceptions. Research shows that there is a gap between what is actually proposed and what is practiced in Colombo in green walls. The study identified the gaps, such as the lack of adaptation to the local environment, proposed what each individual needs to improve to curtail the


Introduction
Today, majority of people live in urban areas. Urbanization attracts many people, which leads to congestion and create explicit issues such as pollution, and diseases and implicit impacts such as climate change. Moreover, residents and visitors may be in danger in the future if these issues escalate.
Should people want to live in non-infectious and risk-free environments, some solutions must be implemented to accommodate Nature in the cities. The best solution would be to use walls of buildings in these areas. Questions may rise how to integrate these buildings with greenery. Thus, architects spend so much time on experimenting and learning how these ideas work and grow sustainably. It is important not only for architects but also for clients, especially because the façade is what people see before visiting a building. Therefore, attention seeking investors implement various strategies to promote their buildings with green walls which are claimed to be eco-friendly and therefore popular.
Green walls could express the quality of the environments. They create positive energy and regenerate a person's immune system if they spend time near them. Some might wonder how to retain plants which are potential air purifiers, produce great scents… etc. It is already proven by modern science and it is no longer difficult to attach natural cleansers to walls.
Colombo has joined the trend of constructing vertical green walls too. Numerous studies on living wall have been published on this topic during the last five years. While these can aid, ideas change as they pass across societies. One of the questions this research aims to investigate is whether there is any gap between the current knowledge of green walls and what is practiced in Colombo? In the Sri Lankan history, vertical gardens have been mentioned related to the pleasure gardens maintained for kings in Sigiriya and in the Giri monasteries. (Bopearachchi,2006) Vertical gardening dates back to days as old as the Mesopotamian era (Petty, 2008). However, the earliest official record comes from Babylon as it had named their vertical gardens as 'hanging gardens of Babylon' (Petty, 2008). According to Petty, the Greeks shared a fair amount of vertical structures for agriculture (2008). In contrast, Romans used their gardens to better environments. Later, it was passed to the Persians (Bowe, 2004). Architect Hector Horeau was one of the first to take advantage of the novel materials of the time for his design for the Parisian boulevard by a light-weight and transparent glass structure that was designed incorporating draping flowering plants. They were installed in pots with soil and were given rainwater harvested from the roof according to the need of the plant. This system of hanging plants became popular and was some of the first examples of Modern vertical gardening methods (Leenhardt and Lambertini, 2007).

Theoretical Basis Background of Vertical Gardening
At end of the 19 th century, 'vertical gardening' was not only a part of a designers' vocabulary but part of botanists and landscape professionals' vocabulary too (Gothein,1966). The first contemporary example of vertical gardening came from a Brazilian landscape architect Roberto Burle Marx (Leenhardt and Lambertini, 2007). He worked on the theory related to plants that grow with little or no soil. This character can be brought to the urban context and as the concept was proven by Safra Bank building, Sao Paolo. At the beginning of the 20 th century, with the influence of the British, architects used climbers to cover the surfaces, especially in cottages and bungalows which could be seen in the Sri Lankan context as well.
General dissatisfaction with the prevailing architectural movement brought a counterculture which saw books like Design with Nature (1968) by Ian McHarg. The work of James Wines, Malcolm Wells, SITE, and others sought to integrate architecture with the principles of Ecological planning (Petty, 2008). As an attempt to create regional specific architecture, some believed regional plant species could be used in buildings to give a specific character. Architect Ken Yeang's Menara Mesiniaga Tower introduces vertical gardening to create a structure that responds to the character of its surrounding ecosystem.
The first contemporary formal use of vertical gardening in Sri Lanka is in the bungalows of the British Period. Kandalama Hotel designed by Architect Geoffrey Bawa is a notable example of the contemporary use of vertical gardening. Clear Point building, Rajagiriya by Archt. Milroy Perera is considered the modernday world's tallest vertical garden building in Colombo. Despite it is seen as a plant tower, it is constructed as garden terraces.

Vertical Gardening
The term 'vertical garden' refers to any system of vertical planting that is attached to either the exterior or interior of a building and is self-sufficient in water and nutrients. These are also referred to as living walls or green walls. The plants receive water and nutrients from within the vertical support instead of from the ground (Tan, 2009). According to Peck (1999), the term 'vertical greenery' is used to define the growing of plants on, up, or against the façade of a building or feature walls. A green wall is essentially a living cladding system using climbing plants with many of the benefits of a green roof. Some have termed it an "organic wallpaper". "Vertical greenery" refers to having vegetation that grows directly onto a building's façade or to vegetation that is grown on a separate structural system that can be freestanding and adjacent or attached to the wall (Loh, 2008).
Modernism is believed to be the culprit behind the decline of green-clad architecture and the incorporation of Nature into a building (Petty, 2008).
The methods/strategies used can be broadly identified as follows.
 Using the building façade as a vertical garden (surface)  Using an additional structure attached to the building façade to act as a vertical garden (single skin)  Using an additional external planting structure detached from the external skin of the building (double skin)  Using horizontal planted terraces as layered vertical gardens on the building façade (layering

Classification of Green Walls
Exterior Interior Boundary Wall  Using the building façade as a vertical garden (surface)  Using an additional structure attached to the building façade to act as a vertical garden (single skin)  Using an additional external planting structure detached from the external skin of the building (double skin)  Using horizontally planted terraces as layered vertical gardens on the building façade (layering) All green walls are vertical gardens but not all vertical gardens are green walls. Main elements of a green wall are plants, planting media, structures that support and attach plants to the façade and irrigation systems (Wood, Bahrami and Safarik, 2014). Green walls have options of camouflage, decorate a building envelop or boundary wall. The stakeholders could also choose when they want to add this to their building. Green walls are listed as two types: as green facades and living walls. Green walls are used for boundary walls and interior as art installations, or as sculpture.
Green walls are mindfully used by architects, landscape architects and designers in creative and innovative ways to achieve various benefits for the buildings and for the people who live in them. Following images are few international examples.
At present, green walls have become more than just walls. Sometimes people are unable to access Nature as there are travel restrictions. In a situation where a city is locked down, it is nice to see Nature next door. Covid-19, for an example, has been a deadly virus that affected travel and tourisms in a way that the people were stuck at home. Residents in the city must have appreciated these green walls as these structures produce scent of a forest and work as an air purifier at the same time.

Types and Technologies in Green Wall Installation Systems/Methods
When considering the technology used in vertical gardening, factors that needs to be considered include: climate (humidity, temperature), orientation, wind, type of vertical gardening system, plants to be used, environmental factors (surrounding ecology), height of building, budget and degree of maintenance (Tan, et al., 2009).Availability of materials and technology, project time line and ability to customize needs to be considered as well.
Newly improved building materials are one aspect of improved vertical garden use. The climbers/ vines are easily supported for longer spans and heights through high tensile steel cables and meshes. Use of geo-textile has prevented roots from rotting and keeps the soil content ideal for growth. Modern automated drip irrigation systems have made it possible to irrigate wider areas and taller structures with minimal human interference, improving cost effective in large projects. Each of the materials changes the aesthetic and functional properties due to the different weight, profile thickness, durability and cost (Perini, et al., 2011).

Green Facades
'Climbing' and 'hanging' are the two types of green façades. Mostly, creepers and vines are involved in this. The climbing method is divided into direct (traditional) and indirect methods.
Guides and modular trellis. Mostly these are commonly practiced using metal mesh, cable supports or rigid system utilizing two/three-dimensional trellis. Examples: -Facade supported green wall with two-dimensional trellis -Facade supported green wall with three-dimensional trellis

Living Walls
These could be achieved by contineous (light weight streams) and modular (Trays, vessel, planter tiles and flexible bags/geo textile pockets) systems. Living walls are divided into two types as 'Hydroponics' and 'Substrate based' types. 'Substrate based' types could be placed vertically, angled or horizontal ways. In places were soil conditions are not suitable for vegetation, a green wall provides an ideal solution to overcome the issue (Eg-Nepal, Sri Lanka). By associating simple techniques and recycled materials, people have shown that vertical gardens are not a luxury but a necessity in these instances.

Concepts of Vertical Gardening in building Facades, Applicable to the City of Colombo
Each building has unique qualities, and these qualities bring attention of the public to places such as entrances. For example, one may have massive arched doorways and towering spires whereas another would pull people in by its welcoming large porch or wide windows.
Façade is the exterior wall or the face of a building as the word means front wall with an entrance, and it undergoes many architectural treatments unlike others. To design a façade, certain elements must be considered starting from entrance features to types of building materials such as stone, wood frames or brick. It is also important to consider fenestration or the size and positioning of windows. As history suggests, architectural styles have been constantly changing and so were facades.
Scientific discoveries suggest that plants in tropical rainforests are capable of surviving on top strata's of the forests in vertical conditions. Thus, they motivate designers to use them in projects such as Green Office-Meudon, Muharraw, Bharain, and Green Gate.
Plants grown in vertical gardens have a higher success rates of survival. Vines and climbers are another option for gardens that stand vertically but the cost of maintenance would depend on the attributes; for example, height of the building, size & type of the system, structure of the system etc. Further, lighting a green wall has become a trend worldwide such as back lit (from inside), wall wash (mount light on surface) & flood lighting (shoot light to surface from a distance).
Colombo has a tropical climate. With high urbanization, Colombo has become a popular place of living but the conversion of green areas to concrete blocks has led to microclimatic changes and phenomenon such as Urban Hear Island (UHI) effects have come to stay. In contrast, green walls, the structures perpendicular to land can reintroduce greenery to the city by integrating vegetation into building envelopes. Besides that, it has other benefits i.e. being an air purifier, long term economic and social benefits such as low energy consumption for cooling systems and sites to visits and enjoy. Buildings also contribute to green economy or vertical gardening would receive credit points under the Sustainable Site category, in Green SL® Rating System of Sri Lanka Green Building Council (SLGBC) for green building certification.
The main purpose of green wall is to replenish air and produce good atmosphere. Colombo has higher number of vehicles that release air filled with carbons. The city is also filled with people who share this air. In addition, people may carry other infections from outer Colombo. Plants in a wall attached to the building should be able to recycle this air and make it disease-free environment to public if correct methodology and plants are available.
There were green walls earlier which had to be taken down due to various reasons (Temple Trees boundary wall, Movepeck Hotel, Hilton Colombo Residencies and Shirohala Petal Guru). The main reason was high maintenance cost.
In 2015, Daily mirror mentioned that the green wall in Temple Trees had cost millions of Rupees per month for maintenance and since it is neither beneficial to the people nor the country, a decision was made to remove it. However, if the green wall was properly designed, there would have been a great overcome and a reduction of cost.

The Role of Green Walls
A building becomes a green building based on how sustainability is achieved through the pre-construction, construction and post construction phases. A wall can be identified as being sustainable in many ways. Green wall is a type of a wall which has vertical gardening.
There are green categories such as LEED, GREENSL, BREEM, Green star etc. These titles are focused on building sustainability but overall, they contain some consideration on the buildings being green by achieving a certain level of vegetation requirement. Green walls represent that role as an option especially in the urban context within a limited plot.
The achievement of the Green Building title has encouraged growing vegetation, but it seems to have become a trend among the urban dwellers. 18 credits can be achieved by the use of a vertical garden in green rating systems like LEED, which in turn can be used as a marketing strategy. Hotels use LEED Certificates as a marketing tool to emphasize its eco-friendly ventures to create an environmentally conscious image to their clients.

Environmental Sustainability of a Green Wall
As the interest has been renewed to improve the way of living in a dense city, vertical greening has become a viable option to mitigate air pollution and global warming. A city's image could be enhanced by embracing vertical gardening. A study in Singapore, for example, shows that, as the city grows, vertical landscaping helps people to relieve stress. Moreover, it is one of the best ways to handle Urban Heat Island (UHI) effect. Renewable source harvest, pollution creation, and non-renewable resource depletion are main considerations of environment sustainability.
The construction industry causes environment pollution by consuming 30-40% energy and natural resources and contribute 30% to greenhouse gas emission. (Loh, 2008) Sustainable building practices can considerably reduce a building's environmental impact in energy consumption. Covering a building envelope with green vegetation is considered a sustainable construction practice, as green vegetation has a positive performance at energy savings, on asthma patients, and air Quality. According to Susan Loh, energy savings evaluated in the energy consumption of the modular panel living wall materials in the manufacturing process and results demonstrate that the modular panel system requires 3 years to balance the energy consumed in the manufacture process. However, the environmental performance of living walls is influenced by the types of materials and plants chosen for the systems, as well as the external factors, such as climate and the building type. Living in a city with polluted or poisonous air is unbearable and lethal. Green walls could mitigate this issue by cleansing the air and killing viruses and bacteria and release antidotes to the environment.

Expectation/Properties of Green Walls Achieving Environmental Sustainability
There are two ways people could gain benefits from environmental sustainability which are direct and hidden. These green walls could act as the natural air purifier. For a long time, the industry has been heavily relying on fossil fuels which produce an abundance of carbon into the atmosphere after its use by vehicles and factories. Some companies may also acquire certain air purifying products that run on electricity which may come from burning coal or something similar. Green walls would help people to stop using electric purifying machines and as the plants absorb lots of carbons for its photosynthesis, it produces fresh oxygen to the air. This would be a great factor when it comes to people who suffer from COVID-19 and shortness of breath. Common reason for shortness of breath is carbon monoxide, as there are less carbon monoxide air, and more oxygen would allow people to breath easily and fight back the COVID-19 virus.
Apart from explicit benefits, there are a number of implicit benefits as well which may not catch people's eye right away. First, the well-being of people inside the building is important and incorporating green walls provide great atmosphere but the green structure would depend on cost, lifespan, maintenance, irrigation, structural support, thermal performance /insulation, energy requirements and climate zone. It is also mentioned about the percentage of green coverage over total area (Wood, Bahrmi and Safarik, 2014). Wender states that being in touch with Nature, has shown to make people happier in general. It is shown that Nature changes brain chemistry in a positive way, improves mood, decreases stress, and provides opportunities for relaxing the mind. (Wender, 1998). Kellert further strengthens this claim by saying it is the spiritual and psychological benefits of Nature which makes it important for people. According to Browne, creating a landscape with natural elements tend to promote psychological and physical benefits (Kellert, 2007). It is easy to point out how people's chemical reactions come to play with these walls during the lock down caused by the COVID-19.
Vertical gardens are now considered part of the landscape field as there are certain things these green walls express such as environmental perception, climate & context, wealth & status (Swaffield,2002). Furthermore, there are rating systems maintained by LEEDS and GreenSL based on management, sustainable sites, energy and atmosphere, materials and resources, indoor environmental quality, innovation and design process, social and cultural awareness.
Criteria for plant selections depend on the types of systems used, the intended planting concept, environmental factors, budget, resilience, disease-tolerance and the expected degree of maintenance (Tan et al., 2009

Primary Observation
It comes from the first stage of the design and they have considered low maintenance and commonly found plants but the structure has been based directly on the supplier's recommendation.

Placement Aspiration & Method
Commercial Credit is a bank which recently rebranded and gave a new look. It is trying to restore all outlets a new brand image. The bank considers the building façade and the placement of green wall as a design requirement and there is a minimum percentage to achieve as a green wall in each outlet façade. As the first attempt of their new concept, this green wall was built at the entrance to emphasize it and to get the attention of the customers.

Data Analysis & Conclusion
Only 36sqm is greenery while rest of the facade which is more than 2/3 is Aluminum cladding and concrete walls. The greenery surface and bthe background incorporates plastic modular pots and PVC pipes for the irrigation system. It acts as completely solid structure imported and assembled in this location. The embodied energy is high. This is not environmentally friendly nor locally produced. It's facing the open area and the façade is exposed to direct sunlight. This wall acts as a dust and sound barrier and provides shade to the entrance area. According to the observations, it's due to water and foliage. It absorbs the heat, unlike the cladding. It is thus aesthetically pleasing. This design has encouraged the use of a variety of plants. It is hard to find any creatures in it.

Case Study 4 -Colombo Courtyard Hotel, Colombo 04
 Above studies show green wall methods used is Colombo are common, inexpensive, low maintenance. "Climbing facades faced supported green wall" is extremely popular.  These walls are yet to catch up as all designs found in Colombo are rigid. Using a robust design can change based on necessity is recommended.  The orientation and placement of irrigation systems are problematic, plants and installation methods should be more responsive to Sri Lankan client.  More issues were observed regarding maintenance equipment.  It is observed that green walls initiated by client and not architects, which is disappointed  Above designs explicitly mark its presence in environmental and greenery discourses but they are still identified as greenwash as participation is not enough and attraction does not help the cause  Green walls commonly used ground plants, air plants, grass types, ferns, and ivies.  Double skin method is the most successful system to achieve bio-climatic benefits such as heat gain reduction, noise reduction and the therapeutic benefits.  Kangaroo pouches/hanging (geo textile) pockets and climbing facades support green walls with three-dimensional trellis are easy to develop locally and easily adaptable to Colombo city.

Conclusions & Recommendations
Are green walls of Colombo meaningfully green? According to this research, they are not environmentally sustainable as they look.
They have achieved aesthetic aspects and given philological impacts, but other aspects are not fulfilled at a satisfactory level. As most of the buildings are air conditioned and have artificially-lit office spaces, the green walls do not provide natural ventilation, lighting or indoor air quality. Moreover, considering the high population density area, people struggle to find actual cleansing effect from these walls during lock-down periods such as COVID-19. Residents did not find any psychological satisfaction.
In conclusion, reality in Colombo city area is way below the idea promoted by environmentalists. Nonetheless, above examples achieved acceptable standards employing inexpensive methods related to the local conditions. It is significant to identify the strengths and build on them towards an environmentally friendly wall system. The architects and architecture programs need to be sensitized.
 Green walls could have extra benefits by having façades that provide herbs to kitchens and potential sales to public  Innovations could provide cost-effective solutions instead of using chemicals. Innovating solutions rainwater for drip irrigation system and sensors to detect dryness, would make maintaining cost effective.  Green walls concept should be promoted to every building regardless of its location  Proposing to use endemic indigenous or local plants for local green walls; such as orchids, Leucas biflora, Impatiens repens, Pyrrosia heterophylla, Evolvulus nummularius, Pothos scandens, Psychotria sarmentosa,Ficus pumila.Common plantsused in Colombo are Bengal clock vine /sky vines (Thunbergia grandiflora) which are fast growing. The higher density of their big leaves can provide privacy.  Kangaroo pouches/Hanging (geo textile) pockets are manufactured with eco-friendly material.  Extra income or tax relief could inspire addition of green walls to any constructions.