Green Façades and Living Walls as Urban Ecosystems: Functions, Constructions and Maintenance from the Architectural Point of View

*Ayşenur Coşkun and Semra Arslan Selçuk* 

### **Abstract**

 The human population is becoming more and more urbanized and there is no doubt that increased urbanization is worsening the quality of life in many cities. Dense buildings and the absence of adequate natural green in urban areas have resulted in local changes in the climatic conditions namely "urban heat island effect" and affected the indoor thermal comfort in all types of buildings. Therefore, urban areas need to be more vegetated to perform as an ecosystem, yet due to the dense urbanization, there is lack of spaces left as plantation areas. Many researches shown that "green roofs" and "green walls" in dense urban areas can perform many different ecosystem services and have a potential to withstand high pollutant environments. From this context, this chapter focuses on "green wall systems" to understand their characteristics, functions, construction methods, and maintenance/operation processes from the architectural point of view. After evaluating the data obtained through selected examples, results show that, there are many parameters that should be considered at the same time—so-called designing with holistic approach—such as suitable support structure, plant selection, appropriate amount of nutrients, water, and suitable lighting conditions to obtain a well-functioning, not superficial and maintainable living wall.

**Keywords:** sustainability, green walls, green façades, living walls, construction, maintenance

#### **1. Introduction**

Urbanization and urban activities, which are one of the biggest problems of today's world, trigger deterioration on natural environments due to their negative effects and cause some environmental problems such as urban heat island (UHI). In this context, researchers, academicians, and actors responsible for the creation of built environments have been examining the issue with different aspects and try to develop sustainable solutions. Green façades and living walls, which have been used for this purpose in recent years is the subject of this study. Covering the external

 walls of the buildings with vegetation especially in dense built environments minimize the negative effects of UHI, besides that can be a solution of the economic, social, and environmental problems such as greenhouse gas (emission) reduction, climate change adaptation, air and noise quality improvements, energy saving, and decorative-esthetic appearance.

 Green walls, a general term used to describe any vegetative wall surface, are known historically since the Roman, Greek Empires, and the Hanging Gardens of Babylon. In the historical process, green walls, which are used for shading and decorative purposes, together with technological developments, contribute to the sustainability performance of the buildings with passive and active design solution. Within the scope of the study, the current green wall systems and their main features were defined, and green wall design examples were examined. The environmental advantages of vertical green wall systems beyond the decorative properties are emphasized.

#### **2. Green wall systems**

 Vegetation can be considered as one of the effective ways of contributing to the built environment with its environmental, economic, and social benefits by increasing the functionality of the building façades [1]. Green walls mean to all systems that ensure the planting of a vertical surface by selecting a variety of plant species, including all growth-oriented solutions [2]. It is possible to classify green walls according to the structural components, growth media, construction technique, plant species, or irrigation systems. In this study, the green walls were divided into two categories as green façades and living wall systems (LWS) in terms of construction technique which is the most common form in literature (**Figure 1**).

**Figure 1.**  *Classification of green wall systems according to their constructional features [3].* 

#### **2.1 Benefits of green wall systems**

#### *2.1.1 Thermal performance in both urban and building scale*

 In dense urban environments where vegetation is not sufficient, unsolicited temperature increases are observed in cities due to the heat being absorbed by the solid surfaces of both buildings and roads. The most basic factors of reducing the negative effects of this situation, which is defined as the effect of urban heat island, are the choice of reflective surface coatings with high albedo (reflectability) *Green Façades and Living Walls as Urban Ecosystems: Functions, Constructions… DOI: http://dx.doi.org/10.5772/intechopen.87836* 

 values and increasing the trees-vegetation surfaces in urban areas [4]. Research conducted in this context shows that planting of the exterior surfaces of the building, increasing the vertical gardens results in to decrease of the urban heat island effect by diminishing the temperature around the buildings. Within this content, it is foreseen that the small-scale valley will be reduced by approximately 9°C by planting on the roofs of the buildings in which a valley in the urban area of Hong Kong. In the same study, it is emphasized that the temperatures are reduced to the optimum levels by green walls and roofs, and they save energy from 32 to 100% in the cooling of buildings [5]. From this point of view, green wall systems can contribute to the cooling and insulation of buildings. For instance, evergreen plants preserve the façade from snow and rain and wind flow in winter seasons [6]. In cold climates, the use of deciduous species in vegetation provides shading in hot summer months while providing solar heat to be spread to the building with the loss of leaves in winter months. Thus, increased thermal performance reduces the energy requirement for heating or cooling a building and CO2 emissions can be reduced [7].

#### *2.1.2 Improving air and acoustic quality*

Vegetation not only release oxygen through photosynthesis by absorbing carbon dioxide, but can also significantly increase indoor air quality, as they also reduce airborne pollutants such as nitrogen oxides and volatile organic compounds [8]. In 2010, at the Delft University of Technology, the result of the experiment showed that vegetation can reduce the number of particles (<10 mm), a long-term threat to human health in the air [9]. In this context, green wall systems contribute significantly to increasing the air quality both inside and outside. In addition to improving air quality, planted surfaces can also be useful for noise pollution by reducing the sound reflection from the solid surfaces of buildings and roads in crowded cities due to the sound absorption characteristics of the leaves [10].

#### *2.1.3 Psychological effects/improvement of health and happiness*

Many studies have been conducted to understand the interaction between human and nature in built environments to increase the quality of life. Researches for office workers in Norway have shown that staff working in offices with indoor vegetation or windows having open view report higher satisfaction [11]. It has been observed that closeness to nature improves productivity in business environments and provides rapid recovery for patients [12]. These biophilic traits promote the use of green wall systems, as part of sustainable design, making mild the harsh climate of urban structures both interior and exterior in increasingly intense urban environments.

#### **2.2 Type of green wall systems**

 According to the construction characteristics with the developing wall technologies, it is possible to examine the green walls as "green façades" and "living walls" by dividing into two main groups and their sub divisions.

#### *2.2.1 Green façades*

Green façades are systems in which climber plants or hanging plants that grow downward when hung to a certain height are grown to cover a desired area. These

#### *ISBS 2019 - 4th International Sustainable Buildings Symposium*

façades can be classified in two groups as direct and indirect. In direct green façades, including traditional green façades, plants are directly attached to the wall or hanged. Indirect green façades have a supporting structure for vegetation. In indirect systems, "continuous" or "modular" solutions are provided, and plants are guided by the support structures such as mostly galvanized or stainless-steel cable, wire or cage. When the vegetation is completely covered in direct systems, it can be very heavy and the risk of falling is increased. In this context, the support structure provided in indirect systems stabilizes the weight of the vegetation and increases its resistance against environmental effects (e.g. wind, rain, and snow). In addition, indirect green façades serve as "double skin façades" by creating an air gap between the building surface and the vegetation (**Figures 2** and **3**). Direct systems in terms of environmental performance and costs can be more sustainable and economical than indirect systems due to their low maintenance requirements and no extra structural materials [3].

#### **Figure 2.**

*Green façades [6]. (a) Direct (traditional) green façade, (b) indirect green façade, and (c) indirect green façade combined with planter boxes.* 

**Figure 3.**  *Details from green façades [13]. (a) Direct green façade and (b) indirect (double skin green) façade.* 

#### *2.2.2 Living walls*

 In order to ensure the integration of green walls into high buildings, the resulting living walls allow for rapid coating of large surfaces with more variety of plant species, more homogeneous growth and adaptation to all kinds of buildings [3]. Living wall systems (LWS) can be categorized as modular or continuous according to application methods (**Figures 4** and **5**). Continuous LWS is based on the application of lightweight and permeable screens where the plants are placed separately.

*Green Façades and Living Walls as Urban Ecosystems: Functions, Constructions… DOI: http://dx.doi.org/10.5772/intechopen.87836* 

**Figure 4.**  *Living walls. (a) Continuous LWS [3] and (b) modular LWS [14].* 

**Figure 5.**  *Details from living walls [13]. (a) Continuous LWS and (b) modular LWS.* 

Modular LWS have elements of a certain size which include modular environments in which plants can grow. Each element is supported by a supplementary structure or fixed directly to the vertical exterior. These elements can be in the form of trays, pots, planter tiles, or flexible bags.

 Water and nutrients for the growth of plants in continuous LWS are provided by a hydroponic method. Hydroponics structures allow the growth of plants without soil by using screens frequently moist by the irrigation system [3]. Differently, in modular LWS, the growth environment is usually provided by filling with soil or artificial growing agents such as foam, felt, perlite, and mineral wool containing an inorganic substrate layer to reduce weight [6]. In terms of environmental performance and cost, green façades have a lower environmental load and cost than living wall systems. Living walls can have negative effects on the environment due to factors such as water consumption, vegetation resistance, and the properties of the structural materials used [3].

#### **3. Case studies on green wall system**

In today's cities, it is obvious that green areas are insufficient. In order to keep people's relationship with nature at the highest level and provide recreational facilities for them, green should take place more in the city. In the planning and growth of healthy, people-oriented, and esthetic cities, it is important to gain vertical green right after the loss of the horizontal green.

 For this purpose, the examples of the buildings with various green wall systems applied and the evaluations showing the effects of these buildings in the city are given in **Tables 1–4**.


#### About the project

 An architectural design with a courtyard and building structure in harmony with the texture and character of the city which has been included in the World heritage list by UNESCO

Building façade is covered with locally found sandstone pieces used in combination with bare concrete slab and several planters in the corridors

With more than 100 concrete planters, the greenery is appearing from all the façades, balconies, and narrow corridors together with rooftop

#### The benefits

Providing solar shading and cooler air to ventilate the spaces due to the plants hanging from the planter boxes arranged throughout the entire façade of the hotel Integration of greenery into the architectural design as a way of revitalizingbuilt environments and contributing to social development Establishing strong relationship between human and nature Positive contribution of oxygen and humidity to micro climate

#### **Table 1.**

*A case on direct green façade usage [15, 16].* 

*Green Façades and Living Walls as Urban Ecosystems: Functions, Constructions… DOI: http://dx.doi.org/10.5772/intechopen.87836* 


About the project


#### The benefits


#### **Table 2.**  *A case on indirect green façade usage [17, 18].*


#### About the project

 • Planted curved façades are very isolated and closed to the neighbors from the north, the east and the south

• Continuous living wall used of exotic plants, with hydroponic irrigation system designed by botanical artist Patrick Blanc

#### The benefits


#### **Table 3.**  *A case on continuous LWT usage [19–21].*

*Green Façades and Living Walls as Urban Ecosystems: Functions, Constructions… DOI: http://dx.doi.org/10.5772/intechopen.87836* 


#### About the project


#### The benefits


#### **Table 4.**

*A case on modular LWT usage [22–24].* 

### **4. Conclusions**

All vertical green wall systems differ with their advantages and disadvantages in terms of construction technique, cost, esthetic, and sustainability potential. The determination of the most suitable system is directly relevant to climate conditions of the location and features such as height of the structure and accessibility. For this reason, it is important to figure out the differences and basic feature of the structures to be applied. The case studies analyzed within the scope of this study have been selected from four different types which are differentiated in terms of construction technique namely: direct green façade, indirect green façade, continuous LWS, and modular LWS. It has been observed that practical solutions provided by vertical green systems have similarities in terms of improvement of biological diversity, positive contribution to micro climate, recovery of lost green, establishing human nature relationship, and esthetic potential. In addition, these systems have structure-specific solutions that improve building's performance, such as insulation, shading, rainwater and waste water recycling, and contribute to energy efficiency. As a result, the contribution of green wall systems to build environment and buildings in the environmental and social context should be evaluated in the future studies, their benefits should be taken into consideration, and the positive effects of these systems should be compared with other constructional solutions. Studies in this field are important in terms of increasing the number of applications in the building façades and thus decreasing the investment and operating costs.

#### **Author details**

Ayşenur Coşkun\* and Semra Arslan Selçuk Department of Architecture, Gazi University, Ankara, Turkey

\*Address all correspondence to: aysenur.zr@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Green Façades and Living Walls as Urban Ecosystems: Functions, Constructions… DOI: http://dx.doi.org/10.5772/intechopen.87836* 

#### **References**

[1] Ottele M, Perini K, Fraaij ALA, Haas EM, Raiteri R. Comparative life cycle analysis for green facades and living wall systems. Energy and Buildings. 2011;**43**:3419-3429. DOI: 10.1016/j. enbuild.2011.09.010

 [2] Newton J, Gedge D, Early P, Wilson S. Building Greener: Guidance on the Use of Green Roofs, Green Walls and Complementary Features on Buildings. London: CIRIA; 2007

[3] Manso M, Castro-Gomes J. Green wall systems: A review of their characteristics. Renewable and Sustainable Energy Reviews. 2015;**41**:863-871. DOI: 10.1016/j. rser.2014.07.203

[4] Ekinci B. Reducing the urban heat Island effect by urban design strategies: Aksaray square case [M.Sc. thesis]. İstanbul: İstanbul Technical University; 2016 (in Turkish)

[5] Alexandri E, Jones P. Temperature decreases in an urban canyon due to green walls and green roofs in diverse climates. Building and Environment. 2006;**43**(4):480-493. DOI: 10.1016/j. buildenv.2006.10.055

 [6] Perini K, Ottelé M, Haas EM, Raiteri R. Vertical greening systems, a process tree for green façades and living walls. Urban Ecosystems. 2013;**16**(2):265-277. DOI: 10.1007/s11252-012-0262-3

[7] Loh S. Living walls—A way to green the built environment. Environment Design Guide. Brisbane: Australian Institute of Architect; 2008;**1**(TEC 26):1-7

[8] Wolverton BC, Wolverton JD. Plants and soil microorganisms: Removal of formaldehyde, xylene, and ammonia from the indoor environment. Journal of the Mississippi Academy of Sciences. 1993;**38**:11-15

 [9] Ottelé M, Van Bohemen HD, Fraaij ALA. Quantifying the deposition of particulate matter on climber vegetation on living walls. Ecological Engineering. 2010;**36**:154-162. DOI: 10.1016/j. ecoleng.2009.02.007

[10] Haron Z, Olham DJ. A Markovian approach to the modelling of sound propagation in urban streets containing trees. In: Conference on Sustainable Building South East Asia, November 2007, Malaysia. 2007

 [11] Dravigne A, Waliczek T, Lineberger R, Zajicek J. The effect of live plants and window views of green spaces on employee perceptions of job satisfaction. HortScience. 2008;**43**(1):183-187. DOI: 10.21273/ HORTSCI.43.1.183

[12] Kellert S. Building for Life: Designing and Understanding the Human-Nature Connection. Washington, DC, USA: Island Press; 2005

[13] Medl A, Stangl R, Florineth F. Vertical greening systems—A review on recent technologies and research advancement. Building and Environment. 2017;**125**:227-239. DOI: 10.1016/j.buildenv.2017.08.054

[14] [Internet]. 2019. https://inhabitat. com/beautiful-vertical-garden-insan-vicente-town-square/ [Accessed: 2019-04-02]

[15] [Internet]. 2019. https://www. archdaily.com/799842/atlas-hotelhoian-vo-trong-nghia-architects [Accessed: 2019-03-30]

[16] [Internet]. 2019. http:// votrongnghia.com/projects/atlas-hotelhoi-an-2/ [Accessed: 2019-03-30]

[17] [Internet]. 2019. https://www. archdaily.com/911296/breathing-housevtn-architects [Accessed: 2019-04-02]

[18] [Internet]. 2019. https://www. dezeen.com/2019/02/09/breathinghouse-vo-trong-nghias-green-wall/ [Accessed: 2019-04-02]

[19] [Internet]. 2019. https://www. archdaily.com/875896/house-in-theoutskirts-of-brussels-samyn-andpartners [Accessed: 2019-03-28]

[20] [Internet]. 2019. https:// samynandpartners.com/portfolio/ house-in-the-outskirts-of-brussels/ [Accessed: 2019-03-28]

[21] [Internet]. 2019. https://www. archweb.it/dwg/Giardini\_verticali/ giardini\_verticali\_muro\_2.html [Accessed: 2019-03-28]

[22] [Internet]. 2019. file:///C:/ Users/%C5%9Fura/Desktop/ Stadskantoor\_Venlo/Case%20Study%20 City%20Hall%20Venlo\_Final\_1.pdf [Accessed: 2019-03-26]

[23] [Internet]. 2019. https://www. kraaijvanger.nl/en/projects/city-hallvenlo/ [Accessed: 2019-03-26]

[24] [Internet]. 2019. https://www. archdaily.com/872129/stadskantoorvenlo-kraaijvanger-architects [Accessed: 2019-03-26]

#### **Chapter 11**
