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- General Introduction
We live in a world where we destroy something which gives us life. we have been constantly destroying our environment to feed our greed. Now that the adverse effects of destroying the nature have given us the fear of getting wiped out of the surface of the planet, we have started to realize the importance of saving our environment. This burden partly lies in the hands of the designer too. So the big question is: how do we design an ecologically responsive built environment?
Giving thought to this question researcher have come up with concepts like ecodesign, where biointegration is done while designing our built environment. In other way it integrates the design and process of built environment with natural environment in a seamless and benign way (Yeang, 2005). In a nutshell, ecodesign is designing the built environment as a system within the natural environment (Yeang, 2005). We cannot achieve 100 percent ecodesign but we can go as far as possible. Everyone should be able to imagine how good it would be when the built environment works as a part of ecosystem where there is no waste and everything works in a flow.
In the struggle for designing a sustainable built environment, integration of vegetation into the building have recently gained popularity mainly in the urban areas where the green space has been substituted by hard pavements. Since nature is as important as our life, lack of green space is a to be look upon. Integrating vegetation into a building has two ways – either vertically or horizontally. Most of the horizontal surface except roof is for functional use for the building users, so the vertical surface becomes the main potential target for such integration since it has lots of surface area left unused.
Rapid urban development has consumed the green space to pave way for buildings and hard surfaces causing an alarming effect on climate. Also for materials used in the buildings, excessive pressure has been put on the resources. To counter such problems different strategy for sustainable built environment has been developed. Greening the vertical exterior envelope can be done through green façade and living wall system while for horizontal envelope is through green roof system. By strategically adding all this green skins, it will be possible to create a network of vegetation linking roofs, walls, courtyards, streets and open spaces (Otelle, 2011).
Such greening strategies of building exterior offers numerous ecological and economical benefits, including stormwater management, energy conservation, mitigation of urban heat island (UHI), reducing air pollutants, increased longevity of buildings, as well as providing a more aesthetically pleasing environment to work and live (Johnstone et al, 2004: Getter et al, 2006; Minke, 1982; Krusche et al, 1982).
- Research Question
What are the generic design criteria for green façade to be used in the urban context of Delhi?
Main research question can be break down into following questions
- Which type of green facade system is available in and around Delhi?
- What kind of green façade is suitable for which kind of project in urban context of Delhi?
- What kind of plant species is suitable for which kind of project and type of system?
3.1 About green façade
Green façade refer to vines and climbers that grow from the ground or from large containers at various locations around the building. The climbers are supported either by the wall itself (the traditional green façade) or by a supporting trellis/mesh (Stav, Yael &Gill, 2012).
Fig: Diagram of green façade according to literature.
a) Plants planted on soil
Plants used in this system are allowed t grow from the ground against the facades. Pants grow in a natural way directly against the façade without using a supporting system. This type of green façade takes relatively long time to grow for full coverage of the façade depending on the amount of wall and the planted species. No watering system is required and it takes water from natural sources like rainwater and groundwater. The category can be divided into self climbing plant system (directly to the wall) and plants which need a supporting structure (indirectly to the wall).
The adhesive roots of the plants help to stick to the surface of the façade and the extent of cover on the façade depends on time, plant species and the spacing between the plants.
Since all the plants don’t have the adhesive properties to attach themselves to the façade to grow on the façade, a supporting structure is designed to help them climb the façade and cover it.
There are two frequently used supporting structure system for greening facades. The supporting system can be divided into following
Modullar trellis panel
The building block of this modular system is a rigid, light weighted, three dimwnsional panel made from powder coated galvanised steel wire that supports plants with both face grid and a panel depth. Since th panels are rigid they can be used either against a wall or freestanding green façade. Freestanding structures can be used as a scree and to isolate views such as fences columns or beside hihways as a noise barier. They can also be used to hide the mechanical equipment, services areas, storage and other buildings aspects that detracts the aesthetics of the building.the panels can be joined and stacked to cover large surface areas or to form different shapes, and are made from recycle content steel.
Cable and wire rope system
the cable and wire rope net system uses either cable and/or wire net. Cables are employed on green facades that are designed to support faster growing plants with denser foliage.wire nets ar ofteen used to support slower gowing plants that need added support. They are more flexible and provide a greater degree of design applications than csbles. Both systems used high tensile steel cables, anchors and supplementary equpments.
b) Plants planted in planter box
In this type of system plants are grown from intermediate planter boxes with soil in it. The planter box can be at the bottom or at the top of the building façade. A continuous watering system is needed for it to thrive as it is not directly planted on the ground. It takes long time to cover the façade. Due to limited pace in the planter box roots cannot grow unlimited as a result of which plants have limitation in width and height they can grow. Thus it is necessary to take planter at each level to cover the façade uniformly with plant.
3.2 Advantages of Green Façade
3.2.1 Air quality improvement and Reducing Carbon Footprint
Otelle (2011) stated that vegetation performs as a sink for particulate matter, especially for finer fractions (smaller than PM 2.5). Leaves of plant provide a large surface area which is capable of filtering out oxides of nitrates, sulphates and carbon dioxide in daytime. A green façade will block the movement of particulate matter particles along the side of the building and filter them (Minke cited in Susorova, 2013). Vegetation has large collecting surface area and promotes also vertical transport by enhancing turbulence (Fowler cited in Susorova, 2013). When concrete, brick stone glass, glass and asphalt surfaces are heated during the summer period, vertical thermal air movements are created and dust particles found on the ground are carried and spread into the air. Particulate matter is adsorbed by tree trunks and twigs and is an efficient for particulate matter fowler et al, 1989).Bussoti (1994) stated that plant barriers immediately along a roadside are more beneficial in capturing the lead and cadmium particles than plants investigated in rural areas.
The greenhouse gases from the atmosphere can be absorbed by the plants and store in their tissues, basically acting as carbon sponges. Therefore the carbon that is sequestered from a 20sqm wall is same as the medium size tree (Patrick, cited in Ling and Hoseini, 2013). Through process of biofiltration, plants and soil which contains the microbes will filter the air and dust that passed through it.
3.2.2 Reduction of urban heat island
The urban island effect caused by temperature difference between the urban area and the surrounding rural areas has been a serious issue from years. The urban centres are significantly hotter because there are many sources of heat vehicle, industries, and mechanical equipment, building materials with hard and reflective surfaces which radiates the heat to the surrounding area and gets trap in the urban canyons. According to Environmental Protection Agency the annual mean air temperature of a city with one million people or more can be 1 degree to 3 degree centigrade warmer than its surroundings. In the evening it can be as high as 12 degree centigrade. UHI increase the cooling load on a building which in turn makes the building to release greenhouse gases and pollute the air.
Plants absorbed the heat and uses in loosing water through evapotranspiration process reducing the surrounding temperatures. Introduction of green spaces will help them reduce it but it will be around that area only that has significant impact. Thus introduction of green facade on buildings gives a uniform mitigation of UHI.
3.2.3 Increase Urban Biodiversity
Building walls and façade provide favorable conditions for certain species of plants and animals. Green facades can be designed as alternative ecological habitats. Green façade provides ecological services like breeding and resting habitat for birds which is an enjoyable sight for human. Facades study in Berlin showed that mainly house sparrows, blackbirds and greenfinches are found between the climbers (Kohler, cited in Ottele, 2011). Green facades hereby functions as a food sources (insects) and as a nesting or breeding opportunities. Kohler concluded from his research that climbing plants form an important habitat for insects. Mainly beetles, flies and spiders are found inside a green façade.
3.2.4 Temperature Regulation, Shading and Insulation
Green facades create their own specific microclimate quite different from its surrounding conditions. The stagnant air layer between the façade and the dense vertical layer has an insulating effect thus acting as extra insulation to the building. Also it blocks the direct which would be falling on the building façade which ensures the temperatures inside the building will be lesser comparing to outside. And in winter it works the other way round by not allowing the heat loss from the building. The green plant layer also reduces the amount of UV light that will fall on the building materials. Since the UV lights deteriorates the materials and mechanical properties of coatings, paints, plastics etc. plants will also have an effect on durability aspects. The denser and thicker the plant layer on the green façade, the more beneficial these effects are.
The energy reductions due to use of green facades were 43% for cooling and 1.2% for heating. Solar transmittance of the foliage which range from 0.43, with a single layer leaves, upto 0.14 with five layers of leaves corresponding to reduction in solar crosses 37% for a layer, upto 86% with five layers of leaves. A green façade with a leaf cover of a size of 5cm yields a k-value of 2.9 W/m2which is comparable with double glazing (Krusche cited in Ottele, 2011).
Fig: improvement of the insulating value of a well greened façade (5cm stagnant air layer between leaves and façade) depending on the U-value of the façade according to Krusche et al, 1982.
3.2.5 Social Impact
People with psychological problems seem to get better when associated with green environment. This phenomenon is called biophillic and suggests that people feel better next to all that is alive and vital (Rudgers cited in Ottele, 2011).past experiments conducted have already proved the positive effects of greenery on human health e.g. it is found that visiting a botanical garden lowers blood pressure and reduces heart rate, Owen cited in Ottele, 2011). Ulrich 1991 shows that presence of vegetation will speed up recovery from stress and in earlier research Ulrich (1984) pointed out that patients who have access to windows had shorter postoperative hospital stays. Additionally, the air filtering and oxygenating abilities of plants can greatly benefit people suffering from breathing diseases caused by urban pollution such as asthma or allergies (peck cited in Susorova, 2013).
3.2.6 Sound insulation
Due to fast urban development many cities are overpopulated. As a result people started settling near expressways or bus terminals exposing occupants to the high level of noise. Cities who are aiming to create a sustainable urban lifestyle have found that greenery is a key element in addressing this noise pollution (Wong cited in Mir, 2011). According to Wong (Cited in Mir, 2011), not all types of vertical green is good in reducing noise. Factors that influence noise reduction include the depth of growing media, materials used as structural components and the overall coverage.
3.2.7 Aesthetic and wall protection against graffiti
Green façade provide aesthetic variation in an environment when the season change and the plant change their color giving it a dynamic environment which people enjoy looking at. Recently aesthetic improvement becoming the main design objective for most of the green façade project. Large parking structures, campus buildings, urban streets, transit shelters, retail buildings etc. all provides an opportunity to design green façade which otherwise would have neglected usually. Implementing patterns, rhythms, and shapes and the use of plant textures and the inviting qualities of designing with nature can all contribute to aesthetic improvement (Peck, cited in Mir, 2011). Another advantage is the protection against unwanted graffiti which otherwise would have invited graffiti artist to do their art in such tempting areas.
Neighborhoods with well designed and maintain green façade systems can increase the property values in between 7%- 15% accordingly absorbing the positive perception of property purchase (Lung and Hoseini, 2012).
Although there are many benefits in reintroducing vegetation to the surfaces of urban buildings and their related spaces, some technical problems are faced during implementation (Johnstone cited in Mir, 2011). Some of the claim disadvantages of green façade are as follows
- Chance of damage on the façade in case of green façade directly to the wall
- Maintenance problems like irrigation and access, periodic checking of cable tensions for proper configuration.
- It might have positive or negative effects depending on the location and due to improper design decisions.
- Excessive moisture retention leads to growth of unwanted algae on the surface.
Most of the researches over green façade are based on western countries and very few in tropical or subtropical regions. Even many of them are in national language so it’s not been translated to add to the local pool of knowledge. Maximum of the research are based on the thermal performance of the green façade. Above that there is no separate research considering only one type of vertical greening system. Usually they kind of talk considering all types of system. Also there is less cost benefit analysis based on different regions due to which it’s difficult to decide the feasibility of any vertical greening system.
- M. Ottele, “The Green Building Envelope – vertical Greening”, Institutional Repository, (2011)
- University of Maryland Extension, “Green facades: Ecologically Designed Vertical Vegetation Helps Create a Cleaner Environment”, (2014)
- Greenscreen, “Introduction to Green Walls Technology, Benefits and Design”, greenscreen.com, (2008)
- Seguridad Sy Medio Ambiente, “Experimental measurement of the contribution of green roofs and green facades to energy savings in Spain”, (2010)
- Y. Staev, “Living Walls and their Potential Contribution to Sustainable Urbanism in Brisbane”, (2008)
- J. Lawrence, “Living Skins: An attribute framework for green façade”, (2001)
- Y. Stave G. Lawson, “Vertical Vegetation Design Decisions and their Impact on Energy Consumption in Subtropical Cities” (2012)
- S. Shweka, N. Magdy, “Green facades as a new sustainable approach climate change”, (2012)
- I. Susorova, “Evaluation of the Effects of Vegetation and Green Walls on Building Thermal Performance and Energy Consumption” (2013)
- K. Yeang, “Green Design in the Hot and Humid Tropical Zone” (2005)
- C.Z. Ling, A.G. Hoseini, “Greenscaping buildings: Amplification of Vertical Greening Towards Approaching Sustainable Urban Structures” (2012)