Vertical greenery systems: A systematic review of research trends

Accepted Manuscript Vertical greenery systems: A systematic review of research trends Rosmina A. Bustami, Martin Belusko, James Ward, Simon Beecham PII:

S0360-1323(18)30603-6

DOI:

10.1016/j.buildenv.2018.09.045

Reference:

BAE 5721

To appear in:

Building and Environment

Received Date: 6 August 2018 Revised Date:

25 September 2018

Accepted Date: 25 September 2018

Please cite this article as: Bustami RA, Belusko M, Ward J, Beecham S, Vertical greenery systems: A systematic review of research trends, Building and Environment (2018), doi: https://doi.org/10.1016/ j.buildenv.2018.09.045. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT

Title: Vertical greenery systems: A systematic review of research trends Rosmina A Bustami a,b,*, Martin Belusko c, James Ward a, Simon Beecham a a

School of Natural and Built Environments, University of South Australia, Mawson Lakes Boulevard, Mawson Lakes, SA 5095, Australia Faculty of Engineering, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia

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Barbara Hardy Institute, School of Engineering, University of South Australia, Mawson Lakes Boulevard, Mawson Lakes, SA 5095, Australia *Corresponding author. Tel: +61 8 83021683; Fax: +61 8 8302 5082

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Email address: [email protected]

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Postal address: School of Natural and Built Environments, University of South Australia, Mawson Lakes Boulevard, Mawson Lakes, SA 5095, Australia

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ACCEPTED MANUSCRIPT Abstract:

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Expansion of modern cities reduces green areas, especially within city centres where the urban heat island has become a significant problem. In an attempt to increase greenery in cityscapes and to provide passive cooling, vertical greenery systems (VGS), an old practice of covering building façades with plants, are receiving attention from architects, engineers, building planners and researchers. This paper systematically reviews available publications on VGS and classifies them according to 13 distinct themes. Research into VGS has increased over recent years and the trend shows the approach to this field of research is changing. Thermal research remains the most prevalent theme compared to others, representing almost half of all publications (76 out of 166), with the top three most highly-cited articles all related to thermal properties of VGS. Nevertheless, the systematic review shows a strong trend of diversification into cross-disciplinary research. The proportion of VGS papers reporting on two or more themes has grown from 25% in 2011 to more than 60% in 2017. The review has revealed that among the limiting factors to VGS are cost and maintenance. The outcomes of this systematic review allow recommendations to be made to architects, designers, planners and owners of VGS regarding the need to account for maintenance in the overall design and operation of these systems. On the basis of this review, future research into VGSs will be increasingly multidisciplinary and will need to consider the interconnected dimensions of the system and how they determine both its cost and effectiveness. Keywords: green façade; living wall; passive cooling; systematic review; vertical greenery system Highlights:

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Increasing research trend in VGS with 42 articles reviewed published in 2017, from 8 in 2010

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Included top ten journals publishing VGS research and top ten cited articles in VGS research

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Trend towards multidisciplinary research of VGS with growing proportion of articles relating to more than one discipline

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Identified emerging research and new technologies in VGS field

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Systematic review on VGS has identified 1000 articles from Scopus and Web of Science with 166 articles included in final review

Introduction

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Population growth and increased urbanisation has reduced the amount of green space within cities, and with it some of the liveability. An additional consequence of urbanisation is increasing heat generated from cities, termed urban heat island (UHI). Vertical greenery systems (VGS) have been proposed as an option for retrofitting passive cooling to a building when installation of other heating or cooling system options are costly and time consuming [1]. VGS refer to plants grown on a vertical profile and may go by the names of vertical greenery system, vertical greenery, vertical garden, vertical green, green wall, vertical landscaping and bioshader [2]. However, these names can be categorised as either green façades or living walls. The categories are based on their construction system. A green façade refers to vegetation grown on or adjoining a building surface. It is available as either a direct also known as a traditional green façade or an indirect green façade which can be grown on continuous guides or trellises (Fig. 1a). Both options can be planted directly in the ground or in planter boxes [3–5] and have a life span of more than 50 years [4]. Climbing plants on green façade was shown to be able to grow from 3 m to 10 m in their first 4 years [6]. The installation, design and maintenance of a green façade is more straightforward compared to living walls. 2

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Living walls, by contrast, refer to vegetation grown in planter boxes which can be developed into modular systems attached to walls without relying on rooting space at ground level and having mechanised watering. Modular panel systems are popular and they can be in the form of trays, vertical or horizontal felt systems (Fig. 1b), among others. This system provides more options for the designer as the field is continuously developing. Living walls allow for hydroponic planting [3] as well as planting in substrate media. The installation is more complicated than green façades and suits both new buildings or for retrofitting projects, with felt pockets having a shorter life span of 10 years, compared to 50 years for those with modular high-density polytethylene (HDPE) pots [4]. Living walls are sometimes located inside a building and referred to as indoor living walls and may specifically be integrated with the building’s mechanical system.

Figure 1 Schematic diagram of examples of different VGS types

VGS including green façades and living walls are relatively common in modern and contemporary structures. VGS have been shown to reduce a building’s façade temperature in the summer and act as an insulator in winter [6–10]. These systems in a built-up urban area create a microclimate such that the space between buildings (termed ‘canyon’) will experience a lower temperature due to the transpiration processes by plants [11–14]. Establishment of VGS have also improved temperature inside buildings, hence reducing energy demand for cooling purposes [15–20]. Direct and indirect benefits of this green infrastructure include noise 3

ACCEPTED MANUSCRIPT reduction [21–25], improved air quality [26–29], increased urban biodiversity [30,31], aesthetics [32], value of a building [32,33] and credits in green building rating system [34,35]. Integrating nature into the modern day architecture offered by VGS (termed biophilic design) can also have a psychological benefit for human health [36]. These other benefits have resulted in a more multidisciplinary focus of research into VGS.

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A growing body of scientific literature on VGS includes studies from all over the world. Nevertheless, VGS impact on heating, ventilation and air cooling (HVAC) is still not well understood. One study has recommended that VGS research be classified according to the Köppen-Geiger climate classification, based on average annual and monthly temperature and rainfall [37].

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VGS research has also been reviewed previously: on thermal benefits including energy savings [37], design, benefits and characteristics of different VGS [38], plant species used [2], carbon sequestration [39] and policy [40]. [41] have recently reviewed key findings in 11 VGS studies. However, a comprehensive systematic review on VGS research across multiple disciplines has not been reported.

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The aim of this systematic review on vertical greenery systems (VGS) is to identify the trends, innovations and future research directions. This review collectively identified research articles in VGS, subdivided them into themes beyond passive heating and cooling benefits, and presented their data systematically. By applying a formal systematic approach and investigating relationships (or gaps) between disciplines, this paper will play a key role in identifying how research into VGS has evolved and forecast future research needs and opportunities. Methods

Identification

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A systematic review is an increasingly popular form of literature review in a range of research fields and is characterised by the fact that it follows a method that is reproducible by other researchers [42]. The systematic review has to be inclusive yet specific. This study adopts a strict protocol with a four-phase process following [43]. This study applies and adopts Moher’s 2010 protocol to focus on outdoor VGS. The four phases for conducting the review are: identification of relevant articles, screening according to established criteria, classification according to themes of articles and their methods, and finalising number of articles for the inclusion for the review.

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The identification phase establishes reproducible search parameters according to eligibility criteria, as well as specifying the database(s) searched. Following the convention of other systematic review papers, Scopus and Web of Science (WoS) were chosen as the two popular indexed electronic databases for their systematic reviews [42]. The search terms were constructed to identify all available papers on VGS, including both outdoor and indoor VGS, and papers within the search criteria which highlighted VGS in their studies. Boolean operators, for example AND, OR, AND NOT, and * were used to be more specific in searching within the databases. Scopus allows users to search deeper than beyond the article’s title, therefore the search was conducted from Title, Abstract and Keywords. Likewise, Web of Science allows for Topic Search that searched within its Title, Abstract, Author keywords and Keywords Plus®. The generic set of search term entered into the two databases was: “Living wall*” OR “Green facade*” OR “Green wall*” OR “Vertical garden*” OR “Vertical green* system. This broad search was deliberately performed to capture the variety of popular terms used to describe VGS. The search was first conducted in November 2017 in both databases and was re-run in January 2018 to include any additional studies published late in 2017.

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ACCEPTED MANUSCRIPT 2.2

Screening

In this phase, studies identified from both databases were screened to exclude articles which were considered ineligible for the review. Thus, the following types of articles were removed: 1. Duplicates 2. Publications not written in English

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3. Non peer-reviewed journal papers, namely letters, conference papers, short notes, books and magazine articles 4. The research was not related or relevant to VGS. This was determined by examining the titles, abstracts, methods and results of each articles. 2.3

Classification

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The remaining articles were classified according to types of VGS, themes and methods. The types of VGS were identified according to whether the articles were reporting on a green façade, a living wall or not specific to one type of VGS (for coding, see Table 1). Some papers reporting on green infrastructures with substantial information on VGS were also included in this classification. Classifications for themes were given to reflect the research focus of each article. Sub-themes were assigned where relevant to research articles with a significant amount of research dedicated to one or more additional fields. The literature was divided into 13 themes, five of which were relatively broad and included numerous concepts or parameters addressed together or in isolation, for example: 1. Thermal related articles – included analysis of temperature, energy savings, heat transfer-related, or analysis of other factors affecting VGS thermal performance such as the distance of air gap and building orientation.

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2. Design – assigned to articles which compared one VGS design to another or introduced a new VGS design. Most review articles presenting benefits of VGS were classified into this theme. 3. Vegetation – included articles with research on plant species used in VGS and some on physiology of the vegetation including leaf-area-index (LAI), transpiration and evapotranspiration rate, or plant growth.

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4. Phytoremediation – included studies on water and air quality, excluding the medium or substrate which has a category on its own.

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5. Economics – included articles which studied economic aspects of VGS including cost–benefit analysis (CBA) or life-cycle analysis (LCA). The remaining categories for themes are acoustics, social studies, biodiversity, irrigation, crop production, medium, maintenance and policy. The articles were also classified according to methods of how the research was conducted. These were review papers, experimental-based research, simulation or modelling-based, a combination of experimental and simulation or modelling approach, or survey or questionnaire.

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ACCEPTED MANUSCRIPT Table 1 Codes and descriptions for classification

$ AC SS BD Irri Med CP M P

Themes Descriptions Thermal Design Vegetation Phytoremediation (including air and water) Economics Acoustics Social studies Biodiversity Irrigation Medium (Substrate) Crop production Maintenance Policy

Code R E S/M E + S/M SQ

Methods Descriptions Review Experimental-based research Simulation/ Modelling Experimental + Simulation/ Modelling Survey/ Questionnaire

Inclusion

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Code T D V PR

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GF LW IGLW GI

Types of VGS Descriptions Not specific to just one type of vertical greening system Specific on green façades Specific on living walls Indoor living walls Green infrastructure

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Code VGS

Studies selected for review in this phase were limited to outdoor VGS focused research, excluding indoor living walls. Hence, articles classified as indoor living walls will not be included. Information on publication year, keywords, citation counts and published journals were extracted from each article. The four-phase process including number of articles reviewed is shown in Fig. 2. 1. Identification

452 records from Web of Science

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548 records from Scopus 2. Screening

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671 after duplicates removed

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632 articles screened

39 non-English articles excluded

369 full text articles assessed for eligibility

263 non-journal articles excluded

3. Classification

231 full-text articles assessed for eligibility

138 articles excluded (not VGS related)

4. Inclusion 166 outdoor VGS articles

Figure 2 Summary of four-phase flow for article inclusion in the review

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Results

Originally 1000 articles were identified from Scopus and Web of Science (WoS) using the generic search term set for this study. During the process, it was found that the search term ‘green wall’ included articles which did 6

ACCEPTED MANUSCRIPT not refer to vertical greenery systems but articles on Great Green Wall projects, commonly in China and Africa, micro-algae related studies on green wall cells and green wall panels, green walls in community separation, building materials made of ‘green’ products, vegetation layers on shotcrete walls and green-coloured walls. Therefore, not only were these studies excluded, but also rather than using the term ‘green wall’, the term ‘Vertical Greenery System’ is adopted to refer to vertical greening on a building façade after Safikhani et al. [2] and Pérez et al.[37].

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After screening, 231 peer-reviewed VGS-related articles were classified. Of these, 18 were studies on indoor living walls and 47 included green infrastructure and urban greening with VGS research. Thus, only 166 articles were research papers specific to outdoor VGS and included in this systematic review.

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The earliest included article identified was published in 1999, and was a quantitative analysis of heat transfer for a two-storey building in Beijing covered in ivy [44]. Nevertheless, in the 1980s researchers had explored different issues and effects of green façade planting [6]. Prior to 2000, about 85% of green façade publications originated from Germany.

Publication trends

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The first patented VGS can be traced to the invention on ‘Botanical Bricks’ by Stanley Hart White in 1938 called ‘Vegetation-Bearing Architectonic Structure and System’ [45]. Then in 1988, French botanist Patrick Blanc patented a modern living wall technique called Mur-vegetal or vertical garden. In this approach, the building façade is covered in felt and plants are grown in an application without a soil medium equipped with a mechanical irrigation system with the provision of additional nutrients [46]. Since then, technical research has focused on the different types of VGS with different themes or emphases such as being thermal or vegetation related or having different analytical approaches. This section discusses the publication trends, the research themes, new technologies introduced and barriers to VGS.

Publication year

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Of the articles reviewed 40% studied living walls, 31% were general VGS papers (VGS or a combination of both GF and LW) and 26% studied green façades (see Fig. 3). The remaining 3% were green infrastructurerelated articles on VGS and green roofs, with a significant research portion on VGS, hence accepted for this review. Thermal-related papers were the most popular theme, followed by design, vegetation and phytoremediation research. The following sections detail the publication trends by year, journals of publication, citation, popular keywords, countries of the research, themes, multidisciplinary research and methods approach by the research.

45 40 35 30 25 20 15 10 5 0

Green façade

Green infrastructure

Living wall

VGS

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

7 1999

Number of articles

The number of publications per year has increased since Köhler’s 2008 [6] visionary article on green façades history and their future potential. The article was a key reference for many of the articles that followed. The number of publications reached 27 in 2014, before dropping to 21 published in 2015. Another trend is that of

ACCEPTED MANUSCRIPT the 42 VGS articles published in 2017, 22 were on living walls. This number is expected to increase in the coming years as research on VGS expands to incorporate more interdisciplinary research and exploration into sustainable materials. Figure 3 Number of VGS papers published by year

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Journal and citation

28

20

11

8 7 7

5 4 3 3 3 3

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Building and Environment Energy and Buildings Ecological Engineering WIT Transactions on Ecology and the Environment Urban Forestry and Urban Greening Acta Horticulturae Urban Ecosystems Applied Energy Journal of Food, Agriculture and Environment Journal of Green Building Renewable and Sustainable Energy Reviews Landscape and Urban Planning Others

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Research into VGS is being published in different subject areas including environmental sciences, engineering, energy, social sciences and material sciences, among others. The most popular journal was Building and Environment with 28 (16%) of the articles reviewed were published. Another 20 articles were published in Energy and Buildings, followed by 11 publications in Ecological Engineering, which emphasises ecosystem restoration. Other popular journals for VGS publications are shown in Fig. 4. These results have shown some clusters of VGS publication isolated in smaller numbers (less than 3 publications in each journal) with 64 publications classified as ‘Others’ scattered out across 60 other journals. This suggests that VGS research is diverse in nature and studied by researchers across a wide range of disciplines, hence multidisciplinary research into VGS is not uncommon.

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64 10

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30 40 Number of articles

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Figure 4 Top journals for VGS publications

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ACCEPTED MANUSCRIPT Citation records from both Scopus and WoS databases showed that the 166 VGS articles reviewed in this study have been cited 2101 times up to end of the year 2017. Despite a lower number of published VGS articles in 2015, citation count increased from 318 in 2014 to 364 in 2015 with a slight increment to 368 in 2016. Citation count in 2017 was more than double the total citation in 2016 (see Fig. 5). As the trend on VGS publication is increasing, the popularity of VGS research is also expected to increase in the coming years. Figure 5 Yearly citation count and a cumulative total of VGS articles

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The top 10 cited articles within this field (up to 2017), according to Scopus, are tabulated in Table 2. The most cited paper was among the first thermal-related studies with large scale experiments on both green façades and living walls [47]. The first article with simulated VGS results was published in 2009 by the same group [48]. Overall, thermal-related articles are among the top cited papers. Reviews by Köhler [6] and Hunter et al. [49] are the two most cited review articles in the field. Among the popular articles cited are the first articles published on air quality improvement [50], acoustics evaluation [22] and life-cycle analysis [51].

1500

775

1000 276

318

<2014

2014

0 Cumulative total

364

368

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500

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2000

2015

2016

2017

Citation count

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No. of citation

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ACCEPTED MANUSCRIPT Table 2 Top-cited articles in VGS up to 2017

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Times cited 144

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119

3

107

4

102

5

93

Article title

Authors

Thermal evaluation of vertical greenery systems for building walls Vertical greening systems and the effect on air flow and temperature on the building envelope Green vertical systems for buildings as passive systems for energy savings Green facades-a view back and some visions

Journal

Wong et al.[47]

Building and Environment

Perini et al.[52]

Building and Environment Applied Energy Urban Ecosystems Ecological Engineering Energy and Buildings Building and Environment Building and Environment Energy and Buildings Ecological Engineering

Pérez et al.[18] Köhler [6]

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Quantifying the deposition of particulate Ottelé et al.[50] matter on climber vegetation on living walls 6 84 Energy simulation of vertical greenery Wong et al.[48] systems 7 81 Thermal performance of a vegetated cladding Cheng et al.[53] system on facade walls 8 71 Acoustics evaluation of vertical greenery Wong et al.[22] systems for building walls Ottelé et al.[51] 9 71 Comparative life cycle analysis for green façades and living wall systems 10 55 Quantifying the thermal performance of green Hunter et al.[5] façades: A critical review T: Thermal; D: Design; PR: Phytoremediation, AC: Acoustics, $: Economics

Popular keywords

Year Published 2010

Theme

2011

T

2011

T

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No.

T

2008

D

2010

PR

2009

T

2010

T

2010

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2011

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2014

T

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Popular keywords used in articles reviewed were analysed and the top 10 most used keywords are listed in Table 3. This analysis combined singular and plural items. The most popular keywords are green wall, green façade, living wall and vertical greenery system. Although scientific studies into VGS have been more receptive towards the term VGS itself, green wall is still a popular keyword.

No.

Keywords

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Table 3 Popular keywords from VGS articles

Green wall(s) Green façade(s)/facade(s) Living wall(s) Vertical greenery system(s)/VGS(s) Vertical garden(s) Living wall system(s) Thermal performance Energy saving(s) Green infrastructure Sustainability

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Author affiliated countries

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1 2 3 4 5 6 7 8 9 10

No. of times used 49 38 27 26 14 14 13 12 10 10

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ACCEPTED MANUSCRIPT Country of origin was analysed based on author affiliations. In events of multiple authors from different countries, all countries are accounted for. The top countries are shown in Fig. 6. Research into VGS is most popular in Europe, confirming the finding by Pérez et al. [37]. 54% of the articles were affiliated with authors from Europe, followed by Asia (29%), North America (7%), Oceania (6%), South America (3%) and Africa (2%). More prominent research was found in hot Mediterranean countries in Europe (e.g. Italy and Spain). Developing countries in Asia are also following this trend.

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30

20 15

Ecuador

Argentina

Venezuela

Chile

New Zealand

Canada

Australia

Greece

Slovenia

Romania

Sweden

United States

N Oceania America

S America

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Themes of VGS articles

Denmark

Portugal

France

Austria

Netherlands

Spain

United Kingdom

Italy

Taiwan

Europe

Figure 6 Author affiliated countries

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Indonesia

Thailand

Iran

India

South Korea

UAE

Malaysia

Japan

Singapore

China

Hong Kong

Asia

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Africa

Egypt

Cape Verde

0

South Africa

5

Norway

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10

Germany

No. of publications

25

The thermal-related theme was the most frequent theme which included articles on temperature, energy and heat properties related to VGS. Of the 166 articles, 76 (46%) articles were in this category. The other main themes of the articles were: design with 24 articles (14%), vegetation and phytoremediation, each with 19 and 15 articles, respectively (11% and 9%) (see Table 4).

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These papers were assessed to classify them into relevant sub-themes. Of these papers, 81 (48.8%) included up to 4 sub-themes. This is an important step to evaluate research articles integrating other themes in their research. These papers were further classified according to the nature of their multidisciplinary research, research methods and new technologies introduced.

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ACCEPTED MANUSCRIPT Table 4 Number of articles in each theme and their methods No. of Sub-theme(s):

Methods

Theme

Total 1

2

3

4

E

E+S/M

S/M

R

SQ

T

42

30

3

-

1

47

13

12

4

-

76

D

20

4

-

-

-

11

-

-

13

-

24

V

7

11

1

-

-

17

1

1

-

-

19

PR

2

13

-

-

-

14

-

1

-

-

15

$

2

6

-

-

1

8

-

1

-

-

9

AC

4

4

-

-

-

3

3

2

-

-

8

SS

4

2

-

-

-

-

-

-

-

6

6

-

-

2

-

-

2

-

-

2

-

-

1

-

-

-

1

-

1

-

1

18

6

166

1

1

-

-

-

2

-

-

1

1

-

-

-

2

-

-

MED

-

2

-

-

-

2

-

-

CP

1

-

-

-

-

1

-

M

-

1

-

-

-

1

-

P

1

-

-

-

-

-

-

Total

85

75

4

-

2

SC

BD IRRI

RI PT

0

M AN U

-

108

17

17

T: Thermal; D: Design; V: Vegetation; PR: Phytoremediation; $: Economics; AC: Acoustics; SS: Social studies; BD: Biodiversity; IRRI: Irrigation; MED: Medium; CP: Crop production; M: Maintenance; P: Policy; E: Experimental; E+S/M: Experimental+simulation/modelling; S/M: Simulation/modelling; R: Review; SQ:Survey/Questionnaire

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Research methods

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Experimental research was the most commonly used method with 108 (65%) papers reviewed adopting experimental research, followed by 18 review articles (11%), 17 articles each for modelling and simulation research, and experimental research with elements of modelling or simulation (10%), and 6 articles on social studies (4%) (see Table 4).

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Almost all thermal-related papers were based on experimental and/or simulation or modelling studies, with only 5% (4 out of 76) being review articles. Vegetation-themed research which may include analysis of the leaf-area index, species, evapotranspiration and plant growth were also mostly experiment-based. However, for designthemed articles, more than half (13 out 24) were review papers. This was mainly due to the fact that most review papers tended to report on general design and benefits associated with VGS, and hence were classified as such as their main theme. There is an increasing trend to experimental based-research and experimental with simulation while modelling research is steady. It can be argued that experimental research is more effective due to the complex systems involved in the modelling process. Multidisciplinary research

A breakdown of multidisciplinary research in VGS according to its published year is tabulated in Table 5. About half of the articles have more than a single theme, with the overwhelming majority (71 articles) of these having a main theme plus one sub-theme. The publication trend is that multidisciplinary research in VGS has increased over the recent years. The two strong multidisciplinary articles were identified, each with a main theme and four sub-themes. One article modelled a one-storey building covered in vegetation with detailed parameters of vegetation, medium, moisture content, irrigation and temperature simulated into its EnergyPlus® model [54]. Another, introduced an

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ACCEPTED MANUSCRIPT innovative approach in VGS design utilising sustainable materials exploring its plant selection, acoustics, mechanical and thermal performances [55]. No papers had three sub-themes. Table 5 Number of multidisciplinary papers according to published year

Total 4 2 4 7 13 10 15 26 81

% of multidisciplinary papers 50% 25% 44.4% 36.8% 48.1% 47.6% 55.6% 61.9% 48.8%

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1 3 1 4 7 13 10 14 23 75

Total papers published 1 1 1 2 8 8 9 19 27 21 27 42 166

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1999 2000 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Total

No. of sub-themes 2 3 4 1 1 1 2 1 4 0 2

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Year

Other multidisciplinary papers with two sub-themes, included an experimental study of a living wall which looked into thermal performance and its relation to irrigation and soil moisture [53], an investigation into crop production for edible and evergreen plants with medium of a living wall in Scandinavian climate [56], a comparison of thermal performance in different VGS designs [57] and an introduction of new technology to evaluate summer green façade cooling magnitude [58]. VGS research trends

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3.2

Thermal

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Although thermal is the most researched theme in VGS, findings from other themes were as important. Research undertaken in other themes showed importance on how VGS was treated as an integrated system. New technologies have emerged due to research advancement in this field, particularly the uptake of sustainable materials to improve the life-cycle analysis and cost–benefit ratio. Information for this review covered laboratory-scale experiments, pilot projects and large-scale projects on state-of-the-art buildings. This section discusses findings of new technologies and advancement of VGS including thermal, design, vegetation, phytoremediation, economics, acoustics, social studies, biodiversity, irrigation and crop production.

Thermal was the most researched topic in outdoor VGS studies. The passive cooling benefits offered by VGS were typically demonstrated by either comparing a control wall surface temperature with VGS covering façade [59–64] or by calculating heat transfer through both control and VGS façades [19,53,65]. Comparisons of green façades and living walls have also been conducted. In tropical Singapore maximum surface temperature reductions of 11.58 ℃ for living walls and 4.36 ℃ for green façade were recorded [47]. A field experiment was conducted in Lleida, Spain on three identical house-like cubicles equipped with an air conditioning heat pump providing heating and cooling in each cubicle – one was a reference structure, one covered with green façade on three sides, and one covered with living wall on three sides. Comparing summer energy consumption against the reference structure yielded 33.8% passive energy saved by the green façadeclad structure and 58.9% saved by the living wall-clad structure [66]. 13

ACCEPTED MANUSCRIPT Heat transfer mechanisms into buildings with VGS were also studied [53,65,67–70]. Reduction of heat flux through building façades with VGS installed can explain the lower façade temperature which are then translated into building energy savings. Reduction of heat flux is possible as the heat is absorbed by VGS’ plants and moist substrates for evapotranspiration and evaporation processes, respectively [71].

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Building orientation also plays an important role in how VGS performs on the growth of plants and amount of solar irradiance received. Hence, more heat flux will be absorbed by VGS into building façades with more vegetation canopy, but more heat will pass through less-shady VGS [67]. A study found the linear relationship of green façade with coverage of vegetation on the building façade [58].

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Studies agreed that when outside conditions are more extreme, the cooling and heating potential gain of a VGS increases. VGS absorbed higher heat flux when solar irradiance is at its highest [66,67,72], and is most effective as winter insulators when the temperature is at its lowest [73,74]. For well-insulated buildings, VGSderived savings from cooling [75] and heating may be not as pronounced [73].

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Heat flux into a building with VGS is reduced in winter. Insulation created by VGS vegetation canopy reduced heat losses from the building into the atmosphere, hence increased the energy efficiency for heating [74,76,77]. In a building with VGS in Hong Kong, in winter the reduction in heat discharge kept the building warmer by up to 3 °C [78].

TE D

Studies into air gap distance between a VGS and the building façade were not conclusive as to whether VGS performance is affected. In one study, a small air gap promoted better cooling performance but increased the humidity of the VGS-façade opening, and may not be ideal in a humid climate [60]. Another study [72] suggested that a deeper gap is preferable, but that study was conducted with limitations that may have affected its results. Hence, more in-depth exploration on how the air gap may affect cooling of a building would be required. Air infiltration into buildings influences a building’s usage of energy for heating and cooling [79,80]. A study on green façades covered in Parthenocissus tricuspidata revealed that the layer of vegetation in front of a building façade reduces air infiltration into the building hence contributed to energy savings [81].

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A lesser impact on temperature fluctuations were recorded in studies comparing a bare wall surface with a vertically vegetated wall [53,59]. Hence, building façades may also be protected from damage caused by rapid temperature fluctuations. VGS has also been compared to other passive cooling designs to achieve thermal comfort [82,83]. The design of passive cooling systems should be carefully considered as what has worked successfully in one climatic setting might not deliver the same benefits in a different climate. Educating building occupants is also important to optimise energy efficiency, and this applies to all passive cooling systems including VGS [83]. A study in Genoa, Italy had a building which extracted air from outside to its room showed fresh air intake behind a VGS could results in intake temperatures up to 10 °C cooler with a monthly average difference of 5 °C in summer, allowing the building to reduce energy for cooling demand by an average of 26% in summer [15]. This improvement represents an indirect benefit, reducing the energy consumption of the mechanical cooling equipment, in addition to the passive cooling benefits for the building itself. Innovations in thermal-related aspects of VGS complement its applications, including introducing a simple sensor platform to measure energy savings in real-time [84]. The platform incorporates input from temperature and energy sensors, occupant and billing information that report the amount of energy saved. This platform was

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ACCEPTED MANUSCRIPT compared to conventional models with theoretical results and showed less than 2% discrepancy. The study showed the platform could be operated simply by a non-professional. A green façade optimisation (GFO) approach was developed to simulate thermal behaviour of a green façade with varying insulation thicknesses [85]. The study used a living wall system planted with sedum showed that a VGS of 3 to 9 cm thickness is ideal, more than 9 cm thickness will not significantly contribute to more energy savings.

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A new method was proposed to evaluate direct green façade cooling benefits from thermal infrared and threedimensional point cloud data in Nanjing, China [58]. Results from this study could be used as a guideline in future green façade and VGS applications. The study found that plant coverage and cooling has a linear relationship, while plant thickness, density and volume are exponentially related to cooling.

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A boundary condition for UHI simulation using VGS was developed in another thermal model [75]. Findings from this study can be expanded further for application in computation fluid dynamics (CFD) simulations of VGS heat flux.

3.2.2

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Studies introducing multifunctional systems whereby a green façade is positioned in a semi-enclosed space between a building surface and photovoltaic panels showed unique management and manipulation of VGS thermal benefits by cooling both the building surface and photovoltaic (PV) panels with the green façade[86] . This system achieved all year round but acted best as insulator in extreme summer condition [87]. However, this system is at the cost of the VGS aesthetics, which may be countered by savings generated from cooling the building and improved PV performance in summer and heating the building in winter. Design

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Most of the papers classified as design-related are review papers presenting benefits of different VGS types. These include characteristics [3], energy savings [2] and experimental setups of experiments [41,88]. A study on viewing VGS as a part of the bigger ecosystem services (ESS), which are more popular in green roofs, discussed that the impact can only be felt with substantial investment into both VGS and green roofs in order to accurately measure ESS benefits [89].

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Innovations in technology associated with VGS systems are aimed at reducing the carbon footprint of existing VGS systems. One method is through the introduction of recycled materials, hence improving the CBA. These innovations mostly concentrated on improving living wall applications. One study demonstrated a prototype solar-powered fertigation system to automate recirculation of drainage back to the system utilising recycled [90]. The system could control irrigation and nutrient amount for each individual pots, allowing customisation of fertigation, irrigation and nutrients of different plant species and substrates; however, the installation of the system is quite complex. The utilisation of recycled materials known as Geogreen is anew modular living wall with an interlocking system. This system demonstrated cooling benefits and claimed to be suitable for both VGS and green roof applications [91]. The system used recycled materials from mine waste (geopolymer) and locally available material such as expanded corkboard along with climate appropriate plants. The materials chosen and system designed was successful in mitigating heat transfer and reduced exterior surface temperature. A new modular living wall was presented using prefabricated lightweight materials with easy installation and maintenance in Italy [92]. This patented felt-pocket living wall system used recycle chair pads as its growing

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ACCEPTED MANUSCRIPT medium. The prototype showed that the materials used in the living wall system and its substrate could reduce thermal transmittance up to 40%.

3.2.3

Vegetation

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Studies have investigated aspects related to vegetation. To minimise maintenance cost and irrigation requirements, utilising perennial and climate appropriate plants for VGS installations is recommended [93]. Studies have utilised perennial plants [56,94,95], drought-tolerant succulent for living walls [3], salt tolerance plants [96] and native plants [59]. Several Mediterranean shrubs were experimented with in living wall studies in Sanremo in Italy and Antibes in France on all four building orientations [97,98]. One recommendation made was to select dwarf varieties of the species to minimise maintenance [98].

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Studies on leaf-area-index (LAI), defined as total leaf area per surface area, mostly of green façades have shown that higher LAI improves VGS thermal performance [2,7,61,99], mainly due to shading and evapotranspiration processes. A study in South Korea confirmed a direct relationship between higher LAI and improved building energy performance for heating and cooling [16]. The magnitude of this cooling is however are dependent on different aspects such as building orientation, climate, humidity, plant type, transpiration rate and thermal properties of the wall. The evapotranspiration process releases latent heat and is unique compared to other shading devices [100], which supported mitigation of UHI in a microclimatic condition. However, for indoor cooling, a study in Japan found that its outdoor green façade vegetation contributes to only up to 9.7% compared to shading alone [101].

Phytoremediation

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3.2.4

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A process tree developed by Perini et al. [4] recommended evergreen shrubs to be planted on living walls, and that evergreen climbing species are preferred for green façades. While addressing preferable vegetation for different VGS designs, the study also addressed different aspects of VGS, hence suitable for new VGS owners to weigh the options on the most suitable VGS systems while addressing environmental concerns, durability and costs associated with installation and maintenance of VGS.

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VGS studies have included the benefit for phytoremediation of air and water. Research on air quality involved assessing claimed benefits of VGS such as carbon sequestration [27,29] and accumulation of particulate matter deposition on the leaves, hence cleaning the air [28,50,51]. Research was also conducted on different vegetations’ air pollution tolerance index [102,103]. In a model for Mediterranean climate, an annual average of 0.44–3.18 kg CO2eq m-2 carbon dioxide captured by VGS was estimated [29]. However, a 6-month experimental study in a tropical setting revealed that VGS plants’ capability in sequestering carbon dioxide is minimum [27]. The results equates to only 2 – 33.6% amount of annual carbon sequestrated suggested by the previous study. However, it could be due to poor plant health in hot summer during the experimental period. Remediating greywater with VGS has also been explored, and although quite limited, the studies have shown promising results in treating contaminants and absorbing nutrients. Irrigating with greywater involves careful design and planning regardless of the VGS size and structure. Among the aspects investigated were plant reactions when irrigated with high salinity content greywater [104]. A study examining soil media impact in treating greywater in living walls found that hydraulically slow media was prone to clogging while the hydraulically fast media had no clogging issues but had a shorter retention time [105]. The study suggested a combination of hydraulically slow and fast media (coir and perlite) for future VGS with greywater operation. 16

ACCEPTED MANUSCRIPT A hydroponic living wall growing lettuce irrigated with treated greywater and urine showed positive results with no E.coli present on plant samples and met minimum health and chemical risks assessment [106]. Forward osmosis water treatment technique utilises osmotic pressure to allow water permeating into its membrane with the help of a draw solution [107]. One option for VGS mitigation is the treatment of raw sewage by forward osmosis integrating liquid fertiliser as its draw solution [108].

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A study found that it is feasible to innovatively demonstrate VGS as an on-site domestic greywater treatment system with a large scale column experiment [109]. The system developed in Melbourne, Australia, was effective at removing suspended solids and organics, but displayed a variable results for phosphorus removal.

3.2.5

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In an industrial example, a living wall built to treat greywater from the food and beverage manufacturing industry prior to discharging into sewers showed a lower concentration of turbidity, biochemical oxygen demand (BOD), total nitrogen and total phosphorus. However, further investigation is recommended to refine its material and optimisation of techniques [110]. One advantage of greywater use is that potable water demand for irrigating VGS can be reduced significantly. This field of studies is relatively new to VGS yet is more established in other green infrastructure research, such as green roofs. The results have been promising and it is expected to be a growing field for future studies. Economics

Cost is a significant but contentious factor in any VGS installation, as the expected benefits from the investment may be (partly or substantially) aesthetic and environmental, so the cost and energy savings may not be directly comparable. This is valid for both green façades and living walls and includes initial and maintenance costs. Initial cost varies with the design and plants, generally with direct green façades being the cheapest of all while modular and felt-layer living walls being the most expensive.

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Quantifiable benefits of VGS in terms of energy saving, increase in property value, carbon dioxide reduction and air quality improvement can all be theoretically weighed against their costs [93]. Government incentives and other social and environmental benefits, such as increased in biodiversity, reduction in microclimate temperature and aesthetics were rarely factored into LCA or CBA quantitative analysis but can be analysed qualitatively [51,93]. Psychological benefits are rarely scientifically addressed [36] hence affects the perspectives of those looking mainly at traditional benefits and their return on investment.

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LCA and CBA applied to VGS showed that direct green façades are favoured for their life-time sustainability [51,93], while modular living walls are more efficient in energy savings. Felt layers are least environmental friendly and sustainable compared to indirect green façades and modular living walls, mainly due to the material used [111]. The payback period of the systems considering only costs and benefits that can be measured and accounted for ranged from 16 to 25 years for direct green façades, 16 to 42 years for indirect green façades, and more than 50 years for modular living walls [93]. Another LCA evaluation factoring energy, water and carbon emissions found that 46% energy usage and 37% carbon emission can be saved by reducing the irrigation amount by half [1]. These studies suggested that payback period and return on investment of VGS takes a long time. They also showed that maintenance is substantial, and needs to be carefully planned and factored into costing of VGS. Through this review, a relatively low number of articles were identified that concentrated on cost-related issues was found compared to VGS research in other disciplines.

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ACCEPTED MANUSCRIPT 3.2.6

Acoustics

Studies into outdoor VGS revealed that both green façades and living walls were capable of increasing acoustic insulation properties of a building [22,23]. Interestingly, installing VGS that simultaneously offer noise reduction benefits and aesthetic benefits are preferred over other measures to control noise [33]. Hence, its relatively higher cost is outweighed by its aesthetic benefits. 3.2.7

Social studies

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Social studies on VGS are relevant as the presence of VGS and biophilic infrastructures have been associated with psychological wellbeing [112]. Three studies have shown that in the results of surveys, VGS were not completely understood to some respondents (83% of building occupants in [32], 40% in [36]), 32% in [112]), while another study on building oppressiveness in an urban environment reported that respondents preferred street trees to buildings with green façades [113].

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In cities which actively introduced greenery in its urban landscape, professionals and end-users did not mutually agree on all VGS benefits and concerns [32]. This Singapore-based study concluded that of importance to achieve the sustainable goal of VGS are the promotion of VGS development which include awareness, technical and maintenance information from professionals and incentives from the government.

3.2.8

Biodiversity

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Positive emotions were reported in 87.7% respondents of a survey conducted for a living wall at a hospital in Seville, Spain. However, willingness to pay (WTP) for the system was quite low with 58.6% respondents indicating the hospital should spend less than €1000 (USD$1175) annually on the living wall [36]. Meanwhile, media coverage saved the equivalent of 660% of its capital cost compared to what would have been spent on advertising. The living wall’s appearances in newspapers, radio and television all contributed to this cost analysis, but not online media.

3.2.9

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Greening the vertical façade of buildings in urban areas presents an opportunity to foster biodiversity in an area that would otherwise be covered in hard walls. Examples in the literature include birds being attracted to green façades in the mornings, possibly due to the presence of food or the more “natural” environment compared with other residential and urban settings [30]. A more widespread observation is that invertebrates (especially beetles and spiders) were found to be significantly more abundant in vegetated façades, especially modular living walls, compared to concrete façades [31].Through ecological engineering approaches to urban design, VGS could offer one pathway to the restoration of ecosystems and ecosystem services that have been displace by conventional urban architecture [9,114]. Irrigation

Articles focusing on irrigation in VGS generally examined two distinct aspects of irrigation systems – amount of irrigation and cost. Adequate irrigation is crucial for plants grown hydroponically and with substrate media. The ideal amount of irrigation duration and frequency for the living wall depends on many factors, including the system design, location and aspect, solar radiation, temperature and humidity, plant species and medium used [115]. Irrigation has also been identified as an important cost-contributing factor. The energy payback period and carbon footprint can be minimised if optimally designed to avoid over-watering of plants, which may be supplemented further with drip irrigation, drought tolerant plants, a rainwater harvesting system, and/or irrigation without a pumping system [1]. Hence, it was advisable to employ higher frequency irrigation with 18

ACCEPTED MANUSCRIPT lower flows and shorter irrigation time in living walls since water distribution uniformity is at its best while the substrate is still moist [115].

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Fertigation, whereby irrigation is combined with fertiliser or other nutrient–riched products, has also recently been introduced into VGS applications [98,116]. Fertigation management was introduced in a living wall experiment in Almeria, Spain, and found that only moderate fertigation was required. The study has also found that fertigation demand in summer months was higher for the top segments of the living walls, up to 60 to 90% more than other segments [116]. Irrigation is crucial in both living walls and green façades VGS. Sufficient irrigation amount is also useful in evapotranspiration process, subsequently promoting thermal cooling. 3.2.10 Crop production

SC

Studies have also explored introducing crop plants for consumption in VGS have also taken place. This creative approach maximises VGS potential and benefits from the produce which could be factored into economics analysis in the future. Integrating urban food production with VGS is possible and has worked well with chives, hyssop, thymes, raspberries and strawberries, along with other perennial plants [56].

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In another successful VGS application, a 7.5 m2 living wall yielded about 55.8 kg of produce valued at USD$527 when harvested in its growing season [117]. Among the crops harvested were basil, chives, cilantro, collards, dill, Asian leafy crop, mustard greens, radishes, salad mix, sugar snap peas, swiss chard and cherry tomatoes. This could be a way forward that could attract domestic living wall applications or when accessibility to the living wall is possible. Barriers to VGS

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Costs, maintenance, and poor financial and energy payback period are among the delimiting factors of VGS [40,51,118,119]. While articles discussed benefits of VGS such as thermal, noticeably fewer articles discussed cost–benefits or LCA, especially as their main theme. The irrigation cost was also claimed as a factor contributing to the high maintenance cost of a VGS [1]. In a study in Singapore, a green maintainability framework for tropical areas was introduced. Maintenance was among the important criteria and parameters in designing stages that should be considered to minimise risk and cost throughout the lifecycle of a VGS [119].

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Other challenges include abiotic and biotic stresses including water stress and frost in continental climates [120]. Among the suggestions were proper selection of plants and substrate medium to maximise effectiveness, otherwise costs will not justify savings generated [83]. External factors such as government incentives, subsidies, establishment of policies and mandatory applications of VGS have certainly contributed to the number of VGS projects being built, as can be seen in Singapore, Germany, Switzerland and Australia, to name a few [40]. However, VGS as a system is relatively new, and will continue to be developed; it has been predicted that a complete guideline standard for VGS is still a decade away [118]. 4

Discussion

Studies in VGS have moved away from discussing solely their thermal benefits, and are increasingly moving into multidisciplinary areas. Research in VGS has diversified from building, energy and engineering fields to multidisciplinary areas including acoustics and social studies. Moreover, VGS studies have diversified from traditional green façades to new technologies in green façades and living walls. This advancement has opened 19

ACCEPTED MANUSCRIPT up research opportunities including the development of new materials to optimise performance, particularly VGS thermal benefit. This review has also identified research undertaken in disciplines indirectly related to VGS, namely sensor development, computer modelling and building materials.

RI PT

Maximum cooling benefits were achieved when VGS were installed on walls receiving higher solar radiation [72]. Moreover, maximum sun exposure orientation is best for optimum plant growth to induce photosynthesis and transpiration. VGS potential and magnitude of benefits, however, may not be the same across all climates and building designs [49]. Plant choice, morphology, design and maintenance may also differ from one climate to another. Advancement in research and technologies will aim to maximise benefits of VGS to suit a climate and building. As VGS is seen as a passive cooling option, thermal studies need to compare it to other passive cooling options.

SC

The success of a VGS relies partly on the ability to select suitable plant species that can maximise the capacity and performance of VGS. Plant selection tends to be covered by general plant selection from other fields, hence studies of plant species for VGS selection should be explored further [7,8]. An extensive plant selection which may involve quality of foliage, colour, texture, leaf shape, plant size, vigour, growth habits [8] and economics (e.g. food crops) should be investigated.

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It is predicted that technical research into VGS will continue to attract interest in the future and that social studies into VGS will become more apparent. Whilst cost is a major factor, harnessing the potential of VGS with other structures or technologies may attract more attention towards a shorter economic payback. Effective measures to reduce irrigation demand should also be examined to reduce costs.

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Expansion in VGS knowledge brings possibilities to further develop the system using state-of-the-art technologies, as shown in studies on developing new and improved thermal benefits [15,86,87] and simulation models [58,75,84,85]. Some challenges around VGS need to be tackled, such as: high initial and maintenance costs, unsustainable materials, complicated design and a short life span [118]. Nevertheless, new technologies and advancement in VGS research are designed to be more cost-effective, aiming at using recyclable and sustainable materials [90–92], irrigating with greywater [105,106,109,110] or using forward osmosis techniques [107,108] and introducing urban food integration [56,117]. A thorough economic analysis should be updated to include costs and savings from introducing new technologies with thermal benefits, usage of more recyclable materials, return on investment from media coverage, recycled irrigation and revenues from crop productions. This approach could provide a platform to narrow the gaps of unknown thermal behaviours [44,85] and difficulties to quantify the full benefits of VGS [1,36,51]. Costs have always been a discriminating factor over VGS’ benefits. Therefore, managers and owners of VGS should accept that albeit with positive thermal profits, VGS are not cheap and demand continuous maintenance. Thus, knowledge of the system should be dissipated to the operators to ensure that maintenance can be acted on. Accepting the results that VGS performed best in poorly insulated buildings, paramount plans for new and well-insulated buildings to be retrofitted with VGS have to be undertaken carefully as to avoid unnecessary additional costs, reduction in energy efficiency and higher carbon footprint with minimal benefits. 5

Conclusions

Each VGS can be unique in terms of its design, system (including plant, substrate media and irrigation), climate and location. Although the capability of VGS as a passive cooling option have been continuously shown, the unique effect of the combination of interrelated variables requires more exploration. Moreover, focusing on only thermal benefits of VGS into the building will risk underestimating the full potential of VGS. VGS should 20

ACCEPTED MANUSCRIPT be seen as a long-term project and all intangible costs and maintenance should be addressed at the conceptual stage. Awareness about how the system works and acceptance of the complexities and potential disadvantages are therefore important in any VGS project, of any size and structure. It is therefore recommended that future studies into VGS – whether as an option for passive cooling, acoustics, aesthetics or a combination of these – should consider the interconnected dimensions of the system and how they determine both its cost and effectiveness.

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Acknowledgements The authors would like to acknowledge University of South Australia for funding and support towards this research. Rosmina A Bustami acknowledges Universiti Malaysia Sarawak for the PhD scholarship award and Dr Monica Behrend for her guidance. References

[5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

[16] [17] [18] [19] [20] [21] [22]

SC

M AN U

[4]

TE D

[3]

EP

[2]

M. Natarajan, M. Rahimi, S. Sen, N. Mackenzie, Y. Imanbayev, Living wall systems: evaluating life-cycle energy, water and carbon impacts, Urban Ecosyst. 18 (2014) 1–11. doi:10.1007/s11252-014-0378-8. T. Safikhani, A.M. Abdullah, D.R. Ossen, M. Baharvand, A review of energy characteristic of vertical greenery systems, Renew. Sustain. Energy Rev. 40 (2014) 450–462. doi:10.1016/j.rser.2014.07.166. M. Manso, J. Castro-Gomes, Green wall systems: A review of their characteristics, Renew. Sustain. Energy Rev. 41 (2015) 863–871. doi:10.1016/j.rser.2014.07.203. K. Perini, M. Ottelé, E.M. Haas, R. Raiteri, Vertical greening systems, a process tree for green façades and living walls, Urban Ecosyst. 16 (2013) 265–277. doi:10.1007/s11252-012-0262-3. A.M. Hunter, N.S.G.G. Williams, J.P. Rayner, L. Aye, D. Hes, S.J. Livesley, Quantifying the thermal performance of green façades: A critical review, Ecol. Eng. 63 (2014) 102–113. doi:10.1016/j.ecoleng.2013.12.021. M. Köhler, Green facades—a view back and some visions, Urban Ecosyst. 11 (2008) 423–436. doi:10.1007/s11252-0080063-x. R.W.F. Cameron, J.E. Taylor, M.R. Emmett, What’s “cool” in the world of green façades? How plant choice influences the cooling properties of green walls, Build. Environ. 73 (2014) 198–207. doi:10.1016/j.buildenv.2013.12.005. N. Dunnett, N. Kingsbury, Planting Green Roofs and Living Walls, Timber Press Inc, Portland, Oregon, 2008. L.-M. Mårtensson, A. Wuolo, A.-M. Fransson, T. Emilsson, Plant performance in living wall systems in the Scandinavian climate, Ecol. Eng. 71 (2014) 610–614. doi:10.1016/j.ecoleng.2014.07.027. T. Safikhani, A.M. Abdullah, D.R. Ossen, M. Baharvand, Thermal impacts of vertical greenery systems, Environ. Clim. Technol. 14 (2014) 5–11. doi:10.1515/rtuect-2014-0007. E. Alexandri, P. Jones, Temperature decreases in an urban canyon due to green walls and green roofs in diverse climates, Build. Environ. 43 (2008) 480–493. doi:10.1016/j.buildenv.2006.10.055. I. Susorova, P. Azimi, B. Stephens, The effects of climbing vegetation on the local microclimate, thermal performance, and air infiltration of four building facade orientations, Build. Environ. 76 (2014) 113–124. doi:10.1016/j.buildenv.2014.03.011. A. Dimoudi, M. Nikolopoulou, Vegetation in the urban environment: microclimatic analysis and benefits, Energy Build. 35 (2003) 69–76. doi:10.1016/S0378-7788(02)00081-6. Q. Chen, B. Li, X. Liu, Cooling effects of the living wall system at different distances to the wall, Int. J. Environ. Sustain. 9 (2013) 67–77. http://www.scopus.com/inward/record.url?eid=2-s2.0-84890211393&partnerID=tZOtx3y1. K. Perini, F. Bazzocchi, L. Croci, A. Magliocco, E. Cattaneo, The use of vertical greening systems to reduce the energy demand for air conditioning. Field monitoring in Mediterranean climate, Energy Build. 143 (2017) 35–42. doi:10.1016/j.enbuild.2017.03.036. S. Poddar, D. Park, S. Chang, Energy performance analysis of a dormitory building based on different orientations and seasonal variations of leaf area index, Energy Effic. 10 (2017) 887–903. doi:10.1007/s12053-016-9487-y. N.H. Wong, A.Y.K. Tan, P.Y. Tan, N.C. Wong, Energy simulation of vertical greenery systems, Energy Build. 41 (2009) 1401–1408. doi:10.1016/j.enbuild.2009.08.010. G. Pérez, L. Rincón, A. Vila, J.M. González, L.F. Cabeza, Green vertical systems for buildings as passive systems for energy savings, Appl. Energy. 88 (2011) 4854–4859. doi:10.1016/j.apenergy.2011.06.032. Y. He, H. Yu, A. Ozaki, N. Dong, S. Zheng, An investigation on the thermal and energy performance of living wall system in Shanghai area, Energy Build. 140 (2017) 324–335. doi:10.1016/j.enbuild.2016.12.083. K.W.D.K.C. Dahanayake, C.L. Chow, Studying the potential of energy saving through vertical greenery systems: Using EnergyPlus simulation program, Energy Build. 138 (2017). doi:10.1016/j.enbuild.2016.12.002. K. V. Horoshenkov, A. Khan, H. Benkreira, Acoustic properties of low growing plants, J. Acoust. Soc. Am. 133 (2013) 2554– 65. doi:10.1121/1.4798671. N.H. Wong, A.Y. Kwang Tan, P.Y. Tan, K. Chiang, N.C. Wong, Acoustics evaluation of vertical greenery systems for building walls, Build. Environ. 45 (2010) 411–420. doi:10.1016/j.buildenv.2009.06.017.

AC C

[1]

21

ACCEPTED MANUSCRIPT

[29] [30] [31] [32] [33]

[34] [35] [36]

[37] [38]

[39] [40]

[41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51]

RI PT

[28]

SC

[27]

M AN U

[26]

TE D

[25]

EP

[24]

G. Pérez, J. Coma, C. Barreneche, A. De Gracia, M. Urrestarazu, S. Burés, L.F. Cabeza, Acoustic insulation capacity of Vertical Greenery Systems for buildings, Appl. Acoust. 110 (2016) 218–226. doi:10.1016/j.apacoust.2016.03.040. M.R. Ismail, Quiet environment: Acoustics of vertical green wall systems of the Islamic urban form, Front. Archit. Res. 2 (2013) 162–177. doi:10.1016/j.foar.2013.02.002. G. Guillaume, B. Gauvreau, P. L’Hermite, Numerical study of the impact of vegetation coverings on sound levels and time decays in a canyon street model, Sci. Total Environ. 502 (2015) 22–30. doi:10.1016/j.scitotenv.2014.08.111. K. Perini, M. Ottelé, S. Giulini, A. Magliocco, E. Roccotiello, Quantification of fine dust deposition on different plant species in a vertical greening system, Ecol. Eng. 100 (2017) 268–276. doi:10.1016/j.ecoleng.2016.12.032. S. Charoenkit, S. Yiemwattana, Role of specific plant characteristics on thermal and carbon sequestration properties of living walls in tropical climate, Build. Environ. 115 (2017) 67–79. https://www.sciencedirect.com/science/article/pii/S0360132317300185 (accessed March 27, 2018). U. Weerakkody, J.W. Dover, P. Mitchell, K. Reiling, Particulate matter pollution capture by leaves of seventeen living wall species with special reference to rail-traffic at a metropolitan station, Urban For. Urban Green. (2017). doi:10.1016/j.ufug.2017.07.005. M. Marchi, R.M. Pulselli, N. Marchettini, F.M. Pulselli, S. Bastianoni, Carbon dioxide sequestration model of a vertical greenery system, Ecol. Modell. 306 (2015) 46–56. doi:10.1016/j.ecolmodel.2014.08.013. C. Chiquet, J.W. Dover, P. Mitchell, Birds and the urban environment: The value of green walls, Urban Ecosyst. 16 (2013) 453–462. doi:10.1007/s11252-012-0277-9. F. Madre, P. Clergeau, N. Machon, A. Vergnes, Building biodiversity: Vegetated façades as habitats for spider and beetle assemblages, Glob. Ecol. Conserv. 3 (2015) 222–233. doi:10.1016/j.gecco.2014.11.016. N.H. Wong, A.Y.K. Tan, P.Y. Tan, A. Sia, N.C. Wong, Perception Studies of Vertical Greenery Systems in Singapore, J. Urban Plan. Dev. 136 (2010) 330–338. doi:10.1061/(ASCE)UP.1943-5444.0000034. K. Veisten, Y. Smyrnova, R. Klæboe, M. Hornikx, M. Mosslemi, J. Kang, Valuation of green walls and green roofs as soundscape measures: Including monetised amenity values together with noise-attenuation values in a cost-benefit analysis of a green wall affecting courtyards, Int. J. Environ. Res. Public Health. 9 (2012) 3770–3778. doi:10.3390/ijerph9113770. M. Weinmaster, Are Green Walls a “Green” as They Look? An Introduction to the Various Technologies and Ecological Benefits of Green Walls, J. Green Build. 4 (2009) 3–18. doi:http://dx.doi.org/10.3992/jgb.4.4.3. X. Wang, X. Liu, Blue Star: The proposed energy efficient tall building in Chicago and vertical city strategies, Renew. Sustain. Energy Rev. 47 (2015) 241–259. doi:10.1016/j.rser.2015.02.047. L. Pérez-Urrestarazu, A. Blasco-Romero, R. Fernández-Cañero, Media and social impact valuation of a living wall: The case study of the Sagrado Corazon hospital in Seville (Spain), Urban For. Urban Green. 24 (2017) 141–148. doi:10.1016/J.UFUG.2017.04.002. G. Pérez, J. Coma, I. Martorell, L.F. Cabeza, Vertical Greenery Systems (VGS) for energy saving in buildings: A review, Renew. Sustain. Energy Rev. 39 (2014) 139–165. doi:10.1016/j.rser.2014.07.055. S. Manso, W. De Muynck, I. Segura, A. Aguado, K. Steppe, N. Boon, N. De Belie, Bioreceptivity evaluation of cementitious materials designed to stimulate biological growth, Sci. Total Environ. 481 (2014) 232–241. doi:10.1016/j.scitotenv.2014.02.059. S. Charoenkit, S. Yiemwattana, Living walls and their contribution to improved thermal comfort and carbon emission reduction: A review, Build. Environ. 105 (2016). doi:10.1016/j.buildenv.2016.05.031. P.J. Irga, J.T. Braun, A.N.J. Douglas, T. Pettit, S. Fujiwara, M.D. Burchett, F.R. Torpy, The distribution of green walls and green roofs throughout Australia: Do policy instruments influence the frequency of projects?, Urban For. Urban Green. 24 (2017) 164–174. doi:10.1016/j.ufug.2017.03.026. A. Medl, R. Stangl, F. Florineth, Vertical greening systems – A review on recent technologies and research advancement, Build. Environ. 125 (2017) 227–239. doi:10.1016/j.buildenv.2017.08.054. A. Mavrigiannaki, E. Ampatzi, Latent heat storage in building elements: A systematic review on properties and contextual performance factors, Renew. Sustain. Energy Rev. 60 (2016) 852–866. doi:10.1016/J.RSER.2016.01.115. D. Moher, A. Liberati, J. Tetzlaff, D.G. Altman, Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement, Int. J. Surg. 8 (2010) 336–341. doi:10.1016/J.IJSU.2010.02.007. H.F. Di, D. Wang, Cooling effect of ivy on a wall, Exp. Heat Transf. 12 (1999) 235–245. doi:10.1080/089161599269708. R.L. Hindle, A vertical garden: origins of the Vegetation-Bearing Architectonic Structure and System (1938), Stud. Hist. Gard. Des. Landscapes. 32 (2012) 99–110. doi:10.1080/14601176.2011.653535. P. Blanc, V. Lalot, The vertical garden : from nature to the city, W.W. Norton, New York, 2008. N.H. Wong, A.Y. Kwang Tan, Y. Chen, K. Sekar, P.Y. Tan, D. Chan, K. Chiang, N.C. Wong, Thermal evaluation of vertical greenery systems for building walls, Build. Environ. 45 (2010) 663–672. doi:10.1016/j.buildenv.2009.08.005. N.H. Wong, A.Y.K. Tan, P.Y. Tan, N.C. Wong, Energy simulation of vertical greenery systems, Energy Build. 41 (2009) 1401–1408. doi:10.1016/j.enbuild.2009.08.010. A.M. Hunter, N.S.G. Williams, J.P. Rayner, L. Aye, D. Hes, S.J. Livesley, Quantifying the thermal performance of green fa??ades: A critical review, Ecol. Eng. 63 (2014) 102–113. doi:10.1016/j.ecoleng.2013.12.021. M. Ottelé, H.D. van Bohemen, A.L.A. Fraaij, Quantifying the deposition of particulate matter on climber vegetation on living walls, Ecol. Eng. 36 (2010) 154–162. doi:10.1016/j.ecoleng.2009.02.007. M. Ottelé, K. Perini, A.L.A. Fraaij, E.M. Haas, R. Raiteri, Comparative life cycle analysis for green façades and living wall

AC C

[23]

22

ACCEPTED MANUSCRIPT

[58]

[59] [60] [61] [62] [63] [64] [65] [66]

[67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80]

RI PT

[57]

SC

[56]

M AN U

[55]

TE D

[54]

EP

[53]

systems, Energy Build. 43 (2011) 3419–3429. doi:10.1016/j.enbuild.2011.09.010. K. Perini, M. Ottelé, A.L.A. Fraaij, E.M. Haas, R. Raiteri, Vertical greening systems and the effect on air flow and temperature on the building envelope, Build. Environ. 46 (2011) 2287–2294. doi:10.1016/j.buildenv.2011.05.009. C.Y. Cheng, K.K.S. Cheung, L.M. Chu, Thermal performance of a vegetated cladding system on facade walls, Build. Environ. 45 (2010) 1779–1787. doi:10.1016/j.buildenv.2010.02.005. Y. Stav, G. Lawson, Vertical vegetation design decisions and their impact on energy consumption in subtropical cities, WIT Trans. Ecol. Environ. 155 (2011) 489–500. doi:10.2495/SC120411. V. Serra, L. Bianco, E. Candelari, R. Giordano, E. Montacchini, S. Tedesco, F. Larcher, A. Schiavi, A novel vertical greenery module system for building envelopes: The results and outcomes of a multidisciplinary research project, Energy Build. 146 (2017) 333–352. doi:10.1016/j.enbuild.2017.04.046. L.-M. Mårtensson, A.-M. Fransson, T. Emilsson, Exploring the use of edible and evergreen perennials in living wall systems in the Scandinavian climate, Urban For. Urban Green. 15 (2016) 84–88. doi:10.1016/J.UFUG.2015.12.001. M. Ottelé, K. Perini, Comparative experimental approach to investigate the thermal behaviour of vertical greened façades of buildings, Ecol. Eng. 108 (2017) 152–161. doi:10.1016/j.ecoleng.2017.08.016. H. Yin, F. Kong, A. Middel, I. Dronova, H. Xu, P. James, Cooling effect of direct green façades during hot summer days: An observational study in Nanjing, China using TIR and 3DPC data, Build. Environ. 116 (2017) 195–206. https://www.sciencedirect.com/science/article/pii/S036013231730080X?via%3Dihub (accessed June 20, 2018). M. Razzaghmanesh, M. Razzaghmanesh, Thermal performance investigation of a living wall in a dry climate of Australia, Build. Environ. 112 (2017) 45–62. doi:10.1016/j.buildenv.2016.11.023. Q. Chen, B. Li, X. Liu, An experimental evaluation of the living wall system in hot and humid climate, Energy Build. 61 (2013) 298–307. doi:10.1016/j.enbuild.2013.02.030. I. Susorova, M. Angulo, P. Bahrami, Brent Stephens, A model of vegetated exterior facades for evaluation of wall thermal performance, Build. Environ. 67 (2013) 1–13. doi:10.1016/j.buildenv.2013.04.027. H.S. Basher, S.S. Ahmad, A.M.A. Rahman, N.Q. Zaman, The use of edible vertical greenery system to improve thermal performance in tropical climate, J. Mech. Eng. 13 (2016) 57–66. M.P. de Jesus, J.M. Lourenço, R.M. Arce, M. Macias, Green façades and in situ measurements of outdoor building thermal behaviour, Build. Environ. 119 (2017) 11–19. doi:10.1016/j.buildenv.2017.03.041. E. Cuce, Thermal regulation impact of green walls: An experimental and numerical investigation, Appl. Energy. 194 (2017) 247–254. doi:10.1016/j.apenergy.2016.09.079. D. Tudiwer, A. Korjenic, The effect of living wall systems on the thermal resistance of the façade, Energy Build. 135 (2017) 10–19. doi:10.1016/j.enbuild.2016.11.023. J. Coma, G. Pérez, A. de Gracia, S. Burés, M. Urrestarazu, L.F. Cabeza, Vertical greenery systems for energy savings in buildings: A comparative study between green walls and green facades, Build. Environ. 111 (2017) 228–237. doi:10.1016/j.buildenv.2016.11.014. C.Y. Jim, Thermal performance of climber greenwalls: Effects of solar irradiance and orientation, Appl. Energy. 154 (2015) 631–643. doi:10.1016/j.apenergy.2015.05.077. C.Y. Jim, Cold-season solar input and ambivalent thermal behavior brought by climber greenwalls, Energy. 90 (2015) 926– 938. doi:10.1016/j.energy.2015.07.127. M. Haggag, A. Hassan, S. Elmasry, Experimental study on reduced heat gain through green façades in a high heat load climate, Energy Build. 82 (2014) 668–674. doi:10.1016/j.enbuild.2014.07.087. R. Djedjig, E. Bozonnet, R. Belarbi, Analysis of thermal effects of vegetated envelopes: Integration of a validated model in a building energy simulation program, Energy Build. 86 (2015) 93–103. doi:10.1016/j.enbuild.2014.09.057. S.C.M. Hui, Z. Zhao, Thermal regulation performance of green living walls in buildings, in: Jt. Symp. 2013 Innov. Technol. Built Environ., Hong Kong, 2013: pp. 1–10. L.S.H. Lee, C.Y. Jim, Subtropical summer thermal effects of wirerope climber green walls with different air-gap depths, Build. Environ. 126 (2017) 1–12. doi:10.1016/j.buildenv.2017.09.021. C. Bolton, M.A. Rahman, D. Armson, A.R. Ennos, Effectiveness of an ivy covering at insulating a building against the cold in Manchester, U.K: A preliminary investigation, Build. Environ. 80 (2014) 32–35. doi:10.1016/j.buildenv.2014.05.020. R.W. Cameron, J. Taylor, M. Emmett, A Hedera Green Façade – Energy Performance and Saving Under Different MaritimeTemperate, Winter Weather Conditions, Build. Environ. (2015). doi:10.1016/j.buildenv.2015.04.011. T. Šuklje, S. Medved, C. Arkar, On detailed thermal response modeling of vertical greenery systems as cooling measure for buildings and cities in summer conditions, Energy. 115 (2016) 1055–1068. doi:10.1016/j.energy.2016.08.095. T. Hong, J. Kim, J. Lee, C. Koo, H.S. Park, Assessment of seasonal energy efficiency strategies of a double skin façade in a monsoon climate region, Energies. 6 (2013) 4352–4376. doi:10.3390/en6094352. J.E. Taylor, R.W.F. Cameron, M.R. Emmett, The role of shrubs and climbers on improving thermal performance of brick walls during winter, Acta Hortic. (2016) 353–359. doi:10.17660/ActaHortic.2016.1108.47. C.Y. Jim, Assessing growth performance and deficiency of climber species on tropical greenwalls, Landsc. Urban Plan. 137 (2015) 107–121. doi:10.1016/j.landurbplan.2015.01.001. G. Happle, J.A. Fonseca, A. Schlueter, Effects of air infiltration modeling approaches in urban building energy demand forecasts, Energy Procedia. 122 (2017) 283–288. doi:10.1016/J.EGYPRO.2017.07.323. K. Gowri, D.W. Winiarski, R.E. Jarnagin, Infiltration modeling guidelines for commercial building energy analysis, United

AC C

[52]

23

ACCEPTED MANUSCRIPT

[87]

[88] [89] [90] [91] [92]

[93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108]

RI PT

[86]

SC

[85]

M AN U

[84]

TE D

[83]

EP

[82]

States, 2009. doi:10.2172/968203. I. Susorova, P. Azimi, B. Stephens, The effects of climbing vegetation on the local microclimate, thermal performance, and air infiltration of four building facade orientations, Build. Environ. 76 (2014) 113–124. doi:10.1016/j.buildenv.2014.03.011. H. Omrany, A. Ghaffarianhoseini, A. Ghaffarianhoseini, K. Raahemifar, J. Tookey, Application of passive wall systems for improving the energy efficiency in buildings: A comprehensive review, Renew. Sustain. Energy Rev. 62 (2016) 1252–1269. doi:10.1016/j.rser.2016.04.010. F. Ascione, Energy conservation and renewable technologies for buildings to face the impact of the climate change and minimize the use of cooling, Sol. Energy. 154 (2017) 34–100. doi:10.1016/j.solener.2017.01.022. Y.C. Tseng, D.S. Lee, C.F. Lin, C.Y. Chang, A novel sensor platform matching the improved version of IPMVP option C for measuring energy savings, Sensors (Switzerland). 13 (2013) 6811–6831. doi:10.3390/s130506811. F. Olivieri, R.C. Grifoni, D. Redondas, J.A. Sánchez-Reséndiz, S. Tascini, An experimental method to quantitatively analyse the effect of thermal insulation thickness on the summer performance of a vertical green wall, Energy Build. 150 (2017) 132– 148. doi:10.1016/j.enbuild.2017.05.068. M.S.P. Moren, A. Korjenic, Green buffer space influences on the temperature of photovoltaic modules, Energy Build. 146 (2017) 364–382. doi:10.1016/j.enbuild.2017.04.051. M.S. Penaranda Moren, A. Korjenic, Hotter and colder – How Do Photovoltaics and Greening Impact Exterior Facade Temperatures: The synergies of a Multifunctional System, Energy Build. 147 (2017) 123–141. doi:10.1016/j.enbuild.2017.04.082. E. Yuksel, A.N. Turkeri, A litterature review of experimental setups monitoring thermal performance of vegetaed facade systems, J. Facade Des. Eng. 5 (2017) 83–101. M.E.C.M. Hop, J.A. Hiemstra, Contribution of green roofs and green walls to ecosystem services of urban green, Acta Hortic. 990 (2013) 475–480. doi:10.17660/ActaHortic.2013.990.61. M. Urrestarazu, S. Burés, Sustainable green walls in architecture, J. Food, Agric. Environ. 10 (2012) 792–794. http://www.scopus.com/inward/record.url?eid=2-s2.0-84856901857&partnerID=tZOtx3y1. M. Manso, J.P. Castro-Gomes, Thermal analysis of a new modular system for green walls, J. Build. Eng. 7 (2016) 53–62. doi:10.1016/j.jobe.2016.03.006. L. Bianco, V. Serra, F. Larcher, M. Perino, Thermal behaviour assessment of a novel vertical greenery module system: first results of a long-term monitoring campaign in an outdoor test cell, Energy Effic. 10 (2017) 625–638. doi:10.1007/s12053016-9473-4. K. Perini, P. Rosasco, Cost–benefit analysis for green façades and living wall systems, Build. Environ. 70 (2013) 110–121. doi:10.1016/j.buildenv.2013.08.012. R.W.F. Cameron, J.E. Taylor, M.R. Emmett, What’s ‘cool’ in the world of green façades? How plant choice influences the cooling properties of green walls, Build. Environ. 73 (2014) 198–207. doi:10.1016/j.buildenv.2013.12.005. L. Jørgensen, D.B. Dresbøll, K. Thorup-Kristensen, Root growth of perennials in vertical growing media for use in green walls, Sci. Hortic. (Amsterdam). 166 (2014) 31–41. doi:10.1016/j.scienta.2013.12.006. L.J. Whittinghill, D.B. Rowe, Salt tolerance of common green roof and green wall plants, Urban Ecosyst. 14 (2011) 783–794. doi:10.1007/s11252-011-0169-4. M. Devecchi, F. Merlo, A. Vigetti, F. Larcher, The cultivation of mediterranean aromatic plants on green walls, Acta Hortic. 999 (2013) 243–247. doi:10.17660/ActaHortic.2013.999.34. F. Larcher, F. Merlo, M. Devecchi, The use of Mediterranean shrubs in green living walls. Agronomic evaluation of Myrtus communis L., Acta Hortic. 990 (2013) 495–500. doi:10.17660/ActaHortic.2013.990.64. G. Pérez, J. Coma, S. Sol, L.F. Cabeza, Green facade for energy savings in buildings : The influence of leaf area index and facade orientation on the shadow effect, Appl. Energy. 187 (2017) 424–437. doi:10.1016/j.apenergy.2016.11.055. M. Scarpa, U. Mazzali, F. Peron, Modeling the energy performance of living walls: Validation against field measurements in temperate climate, Energy Build. 79 (2014) 155–163. doi:10.1016/j.enbuild.2014.04.014. T. Koyama, M. Yoshinaga, K. ichiro Maeda, A. Yamauchi, Transpiration cooling effect of climber greenwall with an air gap on indoor thermal environment, Ecol. Eng. (2015). doi:10.1016/j.ecoleng.2015.06.015. A.K. Pandey, M. Pandey, B.D. Tripathi, Assessment of Air Pollution Tolerance Index of some plants to develop vertical gardens near street canyons of a polluted tropical city, Ecotoxicol. Environ. Saf. (2016). doi:10.1016/j.ecoenv.2015.08.028. A.K. Pandey, M. Pandey, B.D. Tripathi, Air Pollution Tolerance Index of climber plant species to develop Vertical Greenery Systems in a polluted tropical city, Landsc. Urban Plan. (2015). doi:10.1016/j.landurbplan.2015.08.014. A. Escalona, M. del C. Salas, C.D.S. Coutinho, M. Guzmán, How does salinity affect mineral ion relations and growth of Lobelia erinus for use in urban landscaping?, J. Food, Agric. Environ. (2013). V. Prodanovic, B. Hatt, D. McCarthy, K. Zhang, A. Deletic, Green walls for greywater reuse: Understanding the role of media on pollutant removal, Ecol. Eng. 102 (2017) 625–635. doi:10.1016/j.ecoleng.2017.02.045. F.E. Eregno, M.E. Moges, A. Heistad, Treated Greywater Reuse for Hydroponic Lettuce Production in a Green Wall System: Quantitative Health Risk Assessment, Water. 9 (2017) 454. doi:10.3390/w9070454. T.-S. Chung, L. Luo, C.F. Wan, Y. Cui, G. Amy, What is next for forward osmosis (FO) and pressure retarded osmosis (PRO), Sep. Purif. Technol. 156 (2015) 856–860. doi:10.1016/J.SEPPUR.2015.10.063. M. Xie, M. Zheng, P. Cooper, W.E. Price, L.D. Nghiem, M. Elimelech, Osmotic dilution for sustainable greenwall irrigation by liquid fertilizer: Performance and implications, J. Memb. Sci. 494 (2015) 32–38. doi:10.1016/j.memsci.2015.07.026.

AC C

[81]

24

ACCEPTED MANUSCRIPT

[116] [117] [118] [119] [120]

RI PT

[114] [115]

SC

[113]

M AN U

[112]

TE D

[111]

EP

[110]

H.S. Fowdar, B.E. Hatt, P. Breen, P.L.M. Cook, A. Deletic, Designing living walls for greywater treatment, Water Res. 110 (2017) 218–232. doi:10.1016/j.watres.2016.12.018. S. Wolcott, P. Martin, J. Goldowitz, S. Sadeghi, Performance of green wall treatment of brewery wastewater, Environ. Prot. Eng. 42 (2016) 137–149. doi:10.5277/epe160411. H. Feng, K. Hewage, Lifecycle assessment of living walls: Air purification and energy performance, J. Clean. Prod. 69 (2014) 91–99. doi:10.1016/j.jclepro.2014.01.041. A. Magliocco, K. Perini, The perception of green integrated into architecture: installation of a green facade in Genoa, Italy, AIMS Environ. Sci. 2 (2015) 899–909. doi:10.3934/environsci.2015.4.899. M. Asgarzadeh, T. Koga, N. Yoshizawa, J. Munakata, K. Hirate, Investigating Green Urbanism; Building Oppressiveness, J. Asian Archit. Build. Eng. (2010). doi:10.3130/jaabe.9.555. W.J. Mitsch, What is ecological engineering?, Ecol. Eng. 45 (2012) 5–12. doi:10.1016/j.ecoleng.2012.04.013. L. Pérez-Urrestarazu, G. Egea, A. Franco-Salas, R. Fernández-Cañero, Irrigation Systems Evaluation for Living Walls, J. Irrig. Drain. Eng. 140 (2014) 04013024. doi:10.1061/(ASCE)IR.1943-4774.0000702. M. Urrestarazu, G. Carrasco, J.E. Álvaro, Design of a Modular Vegetative Unit and Fertigation Management for NoiseAbatement Walls in a Semiarid Climate, J. Irrig. Drain. Eng. 143 (2016) 1–6. doi:10.1061/(ASCE)IR.1943-4774.0001147. L. Nagle, S. Echols, K. Tamminga, Food production on a living wall: pilot study, J. Green Build. 12 (2017) 23–38. doi:10.3992/1943-4618.12.3.23. B. Riley, The state of the art of living walls: Lessons learned, Build. Environ. 114 (2017) 219–232. doi:10.1016/j.buildenv.2016.12.016. M.Y.L. Chew, S. Conejos, Developing a green maintainability framework for green walls in Singapore, Struct. Surv. 34 (2016) 379–406. doi:10.1108/SS-02-2016-0007. A. Wolter, F.G. Schroeder, Effect of drought stress on the productivity of ivy treated with rhizobacterium Bacillus subtilis, Acta Hortic. 1004 (2013) 107–114.

AC C

[109]

25