Design Guideline For Sustainable Green Roof System

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vegetation on the top of the building roof [1]. The vegetation is planted in a layer of soil or growing medium as the top layer of the roof. ..... three of the four top.
Design Guideline For Sustainable Green Roof System Haziq Abd Aziz and Zulhabri Ismail Legal Aspects in Built Environment Initiative Group Universiti Teknologi MARA (UiTM) 40450 Shah Alam, Selangor [email protected], [email protected]

Abstract— Green roof system has many potential benefits such as environmental benefits, amenity and aesthetic benefits, and economic benefits. The principal aim of this research is to improve the quality of green roof systems in Malaysia by developing design guidelines for green roof systems. This research will identify the performance benefits of green roof, the current phenomenon of green roof as well the obstacles to adopt green roof system. Mixed method of qualitative and quantitative approach will be applied in this research. The review of the literature will be conducted to gather information about green roof in order to identify the benefits of green roof systems. Surveys will be conducted among two target populations, namely developers and architects who work in the Malaysian construction industry. Developers and architects will be selected because of their involvement in the design stage of the building construction. Case study will be the important component to achieve the objectives of this research. This research is attempted to develop design guidelines for green roof systems in Malaysia. The findings from this research will hopefully open new avenues and fields for future researchers and academicians to carry out extensive researches on the topics concerned. Keywords-Green roofs, Global warming, Energy saving, Design guidelines, Environmental impact.

I.

GREEN ROOF SYSTEM

The green roof is a system that used growing medium and vegetation on the top of the building roof [1]. The vegetation is planted in a layer of soil or growing medium as the top layer of the roof. The water membrane system is positioned between growing medium and roof deck to carry away access water and have a filter system to make sure that the plants have a sufficient water supply during drier days [2]; [3]. Green roofs have been increasingly popular in Germany, United States of America and Europe [4] not just because of the aesthetic value, but also for improving environment [5]. As discussed by [6] the roof of a building can be partially or completely covered with a layer of vegetation. Experts confirmed that green roof can be classified into two types of systems which are intensive and extensive [1]; [2]; [6]; [7]. Intensive systems are more like a roof garden supporting large tree and shrubs, but require deep substrates and regular maintenance. Therefore, it is generally heavy and requires a specific support from the building [1]; [7]. The extensive system, however has a thin substrate layer with low level planting, typically sedum or lawn, and can be very light weight in structure [6]. Roofs with extensive systems require little or no additional structural support from the building, are less expensive, need low maintenance and are designed for limited human access. Plants selected for

extensive systems usually have shallow root system, good regenerative abilities, resistance to direct solar radiation, harsh winds or heavy rainfall and are commonly cover species on slopes of up to 30% [1]; [2]. Green roofs have many potential benefits that may fall into three main categories which are amenity and aesthetic benefits, environmental benefits, and economic benefits [8]. Amenity and aesthetic benefits include leisure and open space, visual aesthetic value, health and therapeutic value, and food production. Environmental benefits include ecological and wildlife value, water management, air quality, sound absorption, and reducing the urban heat island effect. Economic benefits include increased roof life, building insulation and energy efficiency, and green building assessment and public relations [9]; [10]. Therefore, it is important to adopt green roof as it gives many benefits to reduce the environmental impact. The purpose of this paper is to provide an overview on the research which is currently undertakes to develop design guidelines for green roof system in Malaysia II.

RESEARCH STATEMENT

Global warming or climate change phenomena have caused environmental issues including higher atmospheric temperatures, intensive precipitation, increase greenhouse gaseous emission and increase indoor discomfort condition [11]. Some scientists believe that changes are part of natural variability [12] while others point to human activity [13]; [14] as the cause of increasing atmospheric concentrations of greenhouse gases (GHGs) as the key driver of climate change. As the carbon dioxide (CO2) in atmosphere is increases, the ability of earth surface to re-radiate heat to atmosphere will decrease. Carbon dioxide acts as a blanket over the surface and keeps the earth warmer than it would otherwise be. The warmer climate outside will also affect the indoor temperature of building. When the outdoor air temperature increases, the occupants in the building will experience discomfort. The demand for mechanical ventilation will be critical and eventually lead to higher energy consumption in building [11]. The heavy reliance on air conditioning typically increases energy use, increased emission of CO2, increase other GHGs to power the system [15] and will also add to negative impacts of global warming [16]. Therefore, it is very important to reduce the energy consumption in building by reducing the usage of air conditioning system where the air conditioning systems release the carbon dioxide into the air which has been

identified as the element that insulates planet and one of the major contributors in global warming. Buildings are important contributors to the increase of carbon emission and its impact on global warming [17]. Buildings last longer, and because of that they contribute to the destruction of environment. Building uses many resources over its life-cycle and is the source of much pollution emissions [18]. In Malaysia, commercial and residential building use up 48% of the electricity generated [17]. During the UN Climate Change Conference in December 2009, Prime Minister Datuk Seri Najib Razak made very clear Malaysia's commitment to the green cause by pledging to cut up to 40 per cent of Malaysia's carbon emission intensity in terms of GDP by the year 2020 from year 2005 levels [19]; [20]. Therefore, one way to reduce the impact of global warming and improve urban environmental quality is by adopting the green roof technologies [21]. However, the question arises, why Malaysian construction industry must adopt the green roof technology? It is because most of the heat, about 75% enters from roof compare to 25% from wall. Besides that, the roof is exposed most for the longest period to solar radiation where heat radiated from the sun is absorbed by the roof surface and the ceiling absorbs the radiated heat [22]. Apart from that, the green roof technology is able to reduce the energy consumption and can improve the internal comfort during the spring and summer seasons [9]; [23]; [24]. Furthermore, green roof lead to lower energy bills, and provide a carbon sink in urban areas, along with many other diverse ecological advantages [25]. Thus, in order to reduce the amount of heat entering through the roofs, such buildings must be equipped with green roof technology. There are few Asian countries which are active in developing green roofs such as Japan, Singapore, Hong Kong and China [26]. According to Wong [27], roofs occupy 21%26% of urban areas worldwide and this provide a unique opportunity to improve the environment. In urban areas such as Kuala Lumpur, there are a lot of opportunities to implement green roofs in the building infrastructure because of rapid development and expansion in this area. By having a green roof, the areas taken from nature to be developed are made to come alive again. Green roofs are considered as a new concept in Malaysia although it offers a lot of benefits. However, Singapore which has similar climate as Malaysia has implemented and progressed with its green roof concept. Compared to Singapore, Malaysia is far behind in terms of research, policies, technologies and practice in this area [26]; [28]; [29]. Malaysia still has many present and potential obstacles such as lack of standards, high costs, inexperienced green roof installers, lack of local research on environmental and economic benefits of green roofs as well as few examples of a constructed Malaysian green roofs [9]; [21]; [25]. Besides that, Malaysia has different climate compared to the temperature regions of the northern hemisphere where green roofs are commonly used. Relying on northern hemisphere research, experience and technology is problematic, due to significant differences in rainfall, temperature, available substrates and suitable vegetation [30]. This may introduce unacceptable levels of risk and unnecessary expense to development projects considering green roofs. Since Singapore

is advanced in developing green roof system, Malaysia should use Singapore concept of green roof as an example to move towards active application of green roof system. In recent years, green roofs are popular and have attracted much attention in Malaysia [26]; [31]. However, people often find it difficult to understand the design factor, maintenance factor, and other requirements needs in order to have an effective systems [32]. Unlike other countries that are very advance in green roof technologies such as Germany and Japan, they have their own guidelines for green roof system [33]. A brief discussion with Ishamuddin Mazlan from Ministry of Energy, Green Technology and Water (KeTTHA) indicates that there are no design guidelines for green roof systems in Malaysia. In German, the German Landscape Research, Development and Construction Society (FLL) has been working on standards for green roof technology for 25 years [34]. Over 800 green roofs can be found in Germany alone, a leader in building codes and incentives for green roof installation. In Asia, Japan has become a centre for green roof technology. Its capital, Tokyo, is the first city to mandate building vegetation must constitute 20 percent of all new construction [35]. Their guidelines are very useful to implement green roof but they should not be copied directly without adapting and considering the local conditions of Malaysia. Therefore, there is an urgent need to develop local design guidelines for green roof systems in Malaysia. III.

THEORETICAL FRAMEWORK

Global warming is one of the greatest challenges to environment and will require global solutions [36]; [37]. The buildings sector which consume about one-third of the world’s energy is the largest source of greenhouse gas emissions [36]; [38]. In Malaysia, energy consumed is 90% in the form of electricity. If these trends continue, energy consumption of buildings will be as much as industry and transport combined [39]. Therefore, the implementation of green roof can solve the environmental issues which mostly occur in urban area. Benefits of green roofs Green roof have a potential to lessen the impact on global warming by reducing energy consumption in the building. This statement is supported by work Fioretti et al [23] whose findings showed green roofs reduced daily energy demand compared to traditional roof. While investigations done by Castleton et al [6] indicated older buildings in UK with green roofs are capable of giving more energy savings than newer buildings equipped with green roofs. Besides that, Wong [27] conducted research on effect of rooftop garden on energy consumption of commercial building in Singapore. Wong study has shown that the installation of rooftop garden in a five-story commercial building could result in a saving of 115% in the annual energy consumption. Thus, these findings indicated that there are relationships between energy consumption in building and environmental impact. Therefore, implementation of green roofs will contribute in reducing the impact of global warming which is an important aspect to be considered in developing the design guidelines.

Another researcher Musa et al [40] discussed on potential of storm water capacity using vegetated roofs in Malaysia. The results showed that the vegetated roof model retained 17 % to 48 % storm water runoff from rainfall. Berghage et al [41] in the findings shown that the green roofs are capable of removing 50% of the annual rainfall volume from a roof through retention and evapotranspiration. Meanwhile Berndtsson et al [42] indicates that both extensive and intensive vegetated roofs are a sink of nitrate nitrogen and ammonium nitrogen. Studies done by Mentens et al [43] and Long et al [2] indicated that green roofs can be a useful tool for reducing urban rainfall runoff and best management practice for urban areas where land for traditional stormwater practices is unavailable. Another research by VanWoert [44] indicates that vegetated green roof systems not only reduced the amount of stormwater runoff, they also extended its duration over a period of time beyond the actual rain event. Therefore, green roofs are important to implement in an urban areas which will aid in retaining stormwater runoff. Authors believe by equipped green roofs in Malaysian buildings especially in urban area will contribute in reducing the flooding issues that happen in an urban area every year. Thus, it can be concluded that stormwater management is one of the most important factors that need to be clearly incorporated in producing design guidelines. Research about green roof materials has been done by Molineux et al [7] on Characterizing alternative recycled waste materials for use as green roof growing media in the U.K. These studies have shown that the alternative substrates perform as well if not better, than the widely used crushed red brick as growing media, in terms of plant growth and material characterizations. These studies give different perspectives that green roofs can be made by using recycle materials rather than natural resources. By using recycle materials, this can contribute to reducing environmental impact. Thus, this will add significant knowledge in formulating guidelines. Maybe the impact of adopting the material selection might not be most suitable since the case is in the UK. Studies by Ismail et al [11] on potted plants as a strategy to reduce indoor temperature in Malaysian climate confirmed that by putting the potted plants on top of the roof, the indoor air temperature of the room underneath significantly reduced. Surface temperatures of roof with potted plants also give a significant reduction which contributed to the reduction of indoor surface temperatures and indoor air temperatures. Since the design roof is conventional, the design has its limits. Thus, in authors opinion, potted plants might be useful in reducing indoor air temperature, nevertheless, it is still cannot provide substantial benefits as green roof systems holistically. Another researcher Renterghem and Botteldooren [45] studies on in-situ measurements of sound propagating over extensive green roofs. This study used experimental approach by measuring sound propagation over flat roofs in five buildings. It shows that green roofs may lead to consistent and significant sound reduction at locations where only diffracted sound waves arrive. While Li et al [5] investigates the effect of green roofs on the ambient CO2 concentration using field measurements, chamber experiments and numerical simulations. Plants can reduce the CO2 concentration in the

environment by absorbing CO2 in the daytime. The findings indicated important elements of green roofs which will reduce CO2 in atmosphere and have a potential to reduce noise from entering the buildings. Therefore, plants selection will be important to be considered in design guidelines because it has to be compatible with environment in Malaysia. Table 1 below illustrates the benefits of green roofs findings by various authors. Table 1: Benefits of green roofs Authors Fioretti et al (2010) Castleton et al (2010)

Wong (2005)

Musa et al (2008) Berghage et al (2009)

Berndtsson et al (2009)

Mentens et al (2006), Long et al (2006)

VanWoert (2005)

Molineux et al (2009)

Ismail et al (2010)

Renterghem and Botteldooren (2011)

Li et al (2010)

Findings Drawn Conclusion Factors Associated Green roofs reduced daily Sustainable building, energy demand compared to energy consumption traditional roof Older buildings with poor Energy consumption, existing insulation are structural capacity, retrofit, deemed to benefit most from insulation a green roof The installation of rooftop Energy consumption, garden in a five-story commercial building commercial building could result in a saving of 1-15% in the annual energy consumption Vegetated roof model Water quantity, stormwater retained 17 % to 48 % storm management, vegetated water runoff from rainfall roofs Green roofs are capable of Stormwater control, design removing 50% of the annual specifications, materials rainfall volume from a roof through retention and evapotranspiration Extensive and intensive Heavy metals, nutrients, vegetated roofs are a sink of runoff quality nitrate nitrogen and ammonium nitrogen Green roofs can be a useful Water retention, urban tool for reducing urban hydrology, runoff, filter rainfall runoff and best media, pollutant loadings management practice for urban areas Vegetated green roof systems Stormwater retention, roof not only reduced the amount surface, sloop, media depth of stormwater runoff, they also extended its duration over a period of time beyond the actual rain event Alternative substrates have Extensive green roof, great potential in the green substrate-based roofs, roof market lightweight aggregates, material characterisation Potted plants on flat roof had Global warming, potted a great potential in reducing plants, indoor temperature, the indoor temperature of the carbon dioxide room underneath and could contributed to the reduction of energy consumption in building. Green roofs may lead to Vegetated roof tops, sound consistent and significant propagation, diffraction, sound reduction at locations acoustic measurements where only diffracted sound waves arrive Air quality, CO2 Plants can reduce the CO2 absorption velocity, concentration in the numerical simulation, field environment by absorbing measurement, chamber CO2 in the daytime experiment

Obstacles of green roofs Although that green roof is very popular in other countries, it seems that each country has obstacles to adopt this system. According to Peck and Callaghan [46] research findings, green

roofs in Canada are not very well utilized due to the few examples of building with green roof systems. This was also supported by Williams [21] which concur that the obstacles exist. In the findings stated that there are many obstacles to implementation of extensive green roofs in Australia. While House [47] has identified the obstacles in green roofs implementation which is lack of adequate research and concerns over cost issues. Meanwhile, study by Zuriea et al [26] indicate that there are several problems identified in existing buildings with green roofs in Malaysia as an obstacle to more adoption of this system. Thus, the findings will add significant values which will assist the research identifications in defining the obstacles and significantly contributes with design guidelines. Table 2 below illustrates the obstacles of green roofs findings by various authors. Table 2: Obstacles of green roofs Authors Peck and Callaghan (1999) Williams (2010)

House (2009)

Zuriea et al (2010)

Findings Drawn Conclusion Factors Associated Green roofs in Canada are Green roofs and vertical not very well utilized due to garden, awareness the few examples of building with green roof systems Many obstacles to Climate, intensiveimplementation of extensive extensive roof gardens, green roofs in Australia irrigation sedum, substrate vegetation Identified the obstacles in Stakeholders, extensive green roofs implementation green roofs, perceptions which is lack of adequate research and concerns over cost issues Several problems identified Perceptions, Facilities in existing buildings with manager, problems with green roofs in Malaysia as an existing green roofs obstacle to more adoption of this system

with cooperation Dubai Green Roof [50]. Their guidelines for planning, execution and maintenance of green roof and wall are very useful for UAE countries. Other studies [51] has been done to develop guidelines for green roof retrofits, including prototype details and specifications for green roof retrofits for the City of Boston’s municipal buildings. Studies by Tolderlund [52] has establishes green roof design, implementation and maintenance recommendations and requirements which apply in general terms to green roofs in the semi-arid and arid regions. However, these guidelines are not suitable to apply in Malaysia because of the different types of environmental conditions but it can be used as a guide in developing design guidelines for green roofs in Malaysia. Currently, there is no clear guideline provided to the Malaysian industry on green roof systems. Therefore, there is an urgent need to develop local design guidelines for green roof systems in Malaysia. Table 3 below illustrates the design guidelines of green roofs findings by various authors. Table 3: Design guidelines of green roofs Authors Hui (2010), Townshend (2007)

Peck and Kuhn (2008)

Velazquez (2005)

Design Guidelines green roofs In this paper, a proposed method is suggested to obtain sufficient information to help in developing design guidelines for green roof system in Malaysia. For instance, Hui [33] has developed technical guidelines for green roof systems in Hong Kong. This paper describes the major findings of a research to develop technical guidelines for green roof systems in Hong Kong. While Townshend [8] conduct a review of the latest concepts and technology on green roofs and recommend guidelines adapted to suit local applications in Hong Kong to promote public understanding and awareness. Thus, this guideline will add significance value in developing design guidelines since the environment in Hong Kong is quite similar as Malaysia. In other countries such as Germany, Canada, Japan, and America, they have their own guideline which has been standardized. Research done by Peck and Kuhn [48] on design guideline for green roofs in Canada provides an introduction to green roof infrastructure and describes how to implement and market a green roof, looks at costs, and presents three case studies. Another researcher Velazquez [49] discusses on the design of green roofs in America with details on system components, maintenance, cost issues, and the range possible applications. In United Arab Emirates (UAE), Dubai has already developed design guidelines by Dubai Municipality

Tolderlund (2010)

IV.

Findings Drawn Conclusion Factors Associated Green roofs can help reduce Develop technical three of the four top guidelines, green roof problems facing the society systems in Hong Kong, such as energy, water, and environment Green roofs are a proven Intensive and extensive technology that provides green roofs, green roof building owners with benefits opportunities to utilize often wasted roof spaces for energy efficiency, storm water management, sound insulation, and aesthetic improvements. Green roofs play an Design of green roofs, important role in promoting system components, sustainable design. maintenance This document offers Green roof types, benefits, guidance on green roof design, maintenance design, implementation and maintenance

AIM AND OBJECTIVES

Generally, this research seeks to have an understanding and knowledge on green roof systems. This proposed study aims to improve the quality of green roof systems in Malaysia by develop design guidelines for green roof systems. In order to achieve the aims above, three (3) correlative objectives are outlined as follows: 1.

To identify the operational performance benefits of green roof technology

2.

To explore the obstacles to adopt green roof technology

3.

To propose a design guideline for green roof systems in Malaysia

V.

RESEARCH METHOD

The methodology will be conducted in three different stages as follows: a)

Literature Search & Review

Literature search will conducted to gather information about green roof in order to identify the benefits of green roof systems. b) Survey Surveys will be conducted among two target populations, namely developers and architects who work in the Malaysian construction industry. Set of questionnaires will be distributed to explore the obstacles to adopt green roof technology in Malaysia. The analysis of data from the questionnaires responses may provide data from which tables of obstacles can be produced. c)

Case Study

Seven case studies will be examined to gain depth understanding on green roofs design from each building equipped with green roofs. The case studies combine different methods to compile an understanding of green roofs systems. As a result the researcher may gain a sharper understanding of why the instance happen as it did, and what might become important factor to be considered when producing the design guidelines of green roofs.

VI.

SIGNIFICANCE OF RESEARCH

This research is expected to identify the performance benefits of green roof systems in Malaysian buildings. Besides that, this research will identify the obstacles to adopt green roof and develop recommendation to overcome this obstacles. Furthermore, this study will add to the body of knowledge that green roof systems can enhance the environment of the urban area, reduce energy use in buildings, and help to reduce effect of global warming especially in urban area in Malaysia. In addition, this proposed research will give better understanding and options for adoption of green roof systems in Malaysian buildings. With this concluded research, it is hoped that new design guidelines for sustainable green roof systems will soon become a reality.

ACKNOWLEDGMENT The author would like to thank the Encik Ishamudin bin Mazlan from the Ministry of Energy, Green Technology and Water (KeTTHA) for providing information regarding this research. The researchers also wish to express their gratitude for the financial support from MOHE (Minister of Higher Education) under Fundamental Research Grant Scheme (FRGS) and UiTM under Excellence Fund Scheme given to this research.

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