Design Guidelines For Sustainable Green Roof Systems Environmental Sciences Essay
In Malaysia, green roofs are considered as a fairly new concept although the concept offers many benefits. Green roofs promotes amenity and aesthetic benefits, environmental benefits, and economic benefits. The principal aim of this research is to improve the quality of green roof systems in Malaysia by develop design guidelines for green roof systems. This research will identify the performance benefits of green roof, the current phenomenon of green roof as well as their obstacles to adopt green roof systems. 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. Survey will be conducted among three target populations, namely developers, architects and landscape architects who work in the Malaysian construction industry. Individuals for the sample group will be selected because as providers of green roofs, their views and actions have a direct influence on green roof development. The categorization of the building professionals will enable easy identification of any disparity in views between them. Besides that, the case studies also one of the vital steps to achieve the objective of this research. The Case Studies will combine different methods to compile an understanding of design guidelines for green roof systems. Case study methods involve an in-depth, longitudinal examination of a single instance or event. They provide a systematic way of looking at events, collecting data, analyzing information, and reporting the results. This research is attempted to develop design guidelines for green roof systems in Malaysia. The findings from this research will 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.
GREEN ROOF SYSTEM
The green roof is a system that used growing medium and vegetation on the top of the building roof (Cresswell, 2007). 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 also have a filter system to make sure that the plants have a sufficient water supply during dryer day (Long et al., 2006, Piper, 2003). Green roofs have been increasingly popular in Germany, United Stated of America and Europe (Koonce, 2010) not just because of the aesthetic value, but also for improving environment (Li et al., 2010). As discussed by (Castleton et al., 2010) the roof of a building can be partially or completely covered with a layer of vegetation. Many expert confirm that green roof can be classified into two types of systems which are intensive and extensive (Long et al., 2006, Molineux et al., 2009, Cresswell, 2007, Castleton et al., 2010). Intensive systems is 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 (Molineux et al., 2009, Cresswell, 2007). The extensive system is opposite of intensive systems which have a thin substrate layer with low level planting, typically sedum or lawn, and can be very lightweight in structure (Castleton et al., 2010). Instead of lightweight, these roofs require little or no additional structural support from the building, less expensive, low maintenance, and designed for limited human access. Plants selected for extensive system are usually have a shallow root system, good regenerative abilities, resistance to direct solar radiation, harsh winds or heavy rainfall, and ground cover species on slopes up to 30% (Long et al., 2006, Cresswell, 2007).
There are many potential benefits of green roofs. These may be considered to fall into three main categories, Amenity and Aesthetic Benefits, Environmental Benefits, and Economic Benefits, although there is a great deal of crossover between categories. Amenity & 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. These benefits operate at a range of scales. Some will only operate if relatively large numbers of green roofs are implemented in any particular area and their benefits will only be apparent at the larger neighborhood or city scale. Others will operate directly on an individual building (Michael and Thomas, 2003, Vancouver, 2009). Therefore, it is important to adopt green roof as it gives many benefits to reduce the environmental impact. The purpose of this research is to develop design guidelines for green roof system in Malaysia.
The phenomenon of global warming or climate change has led to many environmental issues including higher atmospheric temperatures, intensive precipitation, increase greenhouse gaseous emission and of course increase indoor discomfort condition (Asmat Ismail et al., 2010). Some scientists believe that changes are part of natural variability (Radhi, 2009) while others point to human activity (Oh and Chua, 2010, Nordell, 2003) as the cause of increasing atmospheric concentrations of greenhouse gases (GHGs) and the key driver of climate change. As the Carbon dioxide (CO2) in atmosphere increases, the ability of earth surface to reradiate heat to the atmosphere is lessen. 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, building will experience indoor discomfort. The demand for mechanical ventilation will be critical and eventually lead to higher energy consumption in building (Asmat Ismail et al., 2010). The heavy reliance on air conditioning typically increases energy use, increased emission of CO2, increase other GHGs to power the system (Calm, 2002) and also adding to negative impacts of global warming (Wilkinson et al., 2007). Therefore, it is vital important to reduce the energy consumption in building by reducing the usage of air conditioning system where the air conditioning systems release the carbon into the air which has been identified as the element that insulates planet and one of the major contributor in global warming.
Buildings are important contributors to the ever-increasing carbon emission and its impact on global warming (Kui, 4 october 2010; The Star, May 2009). Buildings last longer, and over that lifetime they play a part in contributing to the destruction of the environment. Over its life cycle, a building uses many resources and is the source of much pollution emissions (Yoon, 2009). In Malaysia, commercial and residential building use up 48% of the electricity generated (Li, 2009). 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, 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 (Singh and Ping, 2010, Fernandez, 2010). Therefore, one way to reduce the impact of global warming and improve urban environmental quality is by adopting the green roof technologies (Williams et al., 2010). However, the question arises, why Malaysian construction industry must adopt the green roof technology? It is because most of the heat 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 (Lu, 2009). 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 (Fioretti et al., 2010, Michael and Thomas, 2003, Lawlor et al., 2006). Furthermore, green roof lead to lower energy bills, and provide a carbon sink in urban areas, along with many other diverse ecological advantages (Sihau, 2009). Thus, in order to reduce the amount of heat entering through the roofs, such buildings must be adopted with green roof technology.
In Asia, the use of green roofs has arisen in Japan, Singapore, Hong Kong and China. Although the idea of green roofs in Asia is new, these countries are active in developing, practicing and conducting research on green roofs, particularly in Singapore (Wan et al, 2010). According to Wong (2005) roofs present 21%-26% of urban areas and this can provide a unique opportunity to improve the environment if green roofs are used. In urban areas such as Kuala Lumpur, there are a lot of opportunities to implement green roofs in the development because of rapid expansion in these areas. By having a green roof, the areas taken from nature to be developed are made to come alive again. Green roofs in Malaysia are considered as a fairly new though lots of benefits are offered. However, in country that has similar climate with Malaysia such as Singapore have grown remarkable on green roof. Compare to Singapore, Malaysia are far behind in terms of research done, policies, technology and practice in this area (Govindaraju et al., 2005, Chandran et al., 2009). Malaysia still remains many potential obstacles to their more widespread adoption. This obstacles include a lack of standards, high costs when green roof installers are inexperienced, few demonstration examples to inspire and give confidence to developers considering a green roof and a lack of relevant and reliable research to provide confidence in the economic and environmental benefits of green roofs (Williams et al., 2010) (Williams et al, 2010; Sihau 2009; Michael & Thomas, 2003). Besides that, Malaysia has a very different climate to the temperature regions of the northern hemisphere where green roofs are more common. Relying on northern hemisphere research, experience and technology is problematic, due to significant differences in rainfall, temperature, available substrates and suitable vegetation (Wilkinson, 2009). This may introduce unacceptable levels of risk and unnecessary expense to development projects considering green roofs. Since Singapore is advance in developing green roof system, therefore Malaysia should put Singapore as an example to move towards green roof system. This research examines green roofs in Malaysia, the status of the industry and discusses information gaps requiring research. Therefore, it is important to overcome the obstacles by adopting green roof technology in Malaysia in order to get the benefits offers from the technology.
In recent years, green roofs are becoming more and more popular in the world and have also attracted much attention in Malaysia. However, when people consider applying green roof systems, they often find it difficult to understand the technical requirements, design an effective system and evaluate their performance. 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 (Hui, 2010). 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. Their ‘Guideline for the Planning, Execution and Upkeep of Green-Roof Sites’ (FLL-guidelines) reflects the latest developments in German acknowledged state-of-the-art technology (Philippi, 2005). 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 center for green roof technology. Its capital, Tokyo, is the first city to mandate building vegetation must constitute 20 percent of all new construction (Wark, 2003). 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.
hghg There were various research has been conducted in the field of green roof systems and the quantity seems to increase over the years since environmental issues become more concerning worldwide. The research that has been done in the field of green roof can be grouped into seven which are research on storm water management, research on materials, research on opportunities and barrier, research on environment, research on energy and building, research on perceptions, and research on guidelines. The research that has been done in storm water management for instance by Berghage et al (2009) conducted a research on Green Roofs for Stormwater Runoff Control. The findings of the paper indicate that the green roofs are capable of removing 50% of the annual rainfall volume from a roof through retention and evapotranspiration. Rainfall not retained by green roofs is detained, effectively increasing the time to peak, and slowing peak flows for a watershed. Whereas Berndtsson et al (2009) conducted a research on Runoff water quality from intensive and extensive vegetated roofs. This study investigated influence on runoff water quality from two full scale vegetated roofs (an intensive from Japan and an extensive from Sweden). Results show that both extensive and intensive vegetated roofs are a sink of nitrate nitrogen and ammonium nitrogen with similar performance. The intensive vegetated roof is also a sink of total nitrogen in contrast to the extensive roof. While Hardin and Wanielista (2007) has done research on a water quality assesment of a green roof stormwater treatment systems. The results of this work show that the use of green roof stormwater treatment systems for the improvement of stormwater quality is a promising treatment option. The total suspended solids results show that green roofs had a lower concentration and smaller standard deviation than the control chambers. Besides, Emilsson et al (2007) has done a research on Effect of using conventional and controlled release fertiliser on nutrient runoff from various vegetated roof systems. The findings of the paper indicate that Conventional fertilisers caused high nutrient concentrations in the runoff water. Concentrations decreased during the duration of the experiment but at the end of the experiment they were still higher than after fertilisation with CRF. Conventional fertiliser also increased the total nutrient runoff.
Research on materials for instance has been done by Molineux et al (2009) on Characterising alternative recycled waste materials for use as green roof growing media in the U.K. This study 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 characterisations.. They are also similar in price to the red brick substrate (Shireminerals, pers. comm.) and are already commercially available. While Cresswell (2007) has done a research on Characterisation of Mineral Wastes, Resources and Processing technologies. The findings indicate that Aerated concrete is a material that is suitable for use as a light weight green roof substrate. It has the appropriate density and water absorption.
Research that has been conducted on opportunities and barrier for instance by Williams et al (2010) on Green roofs for a wide brown land: Opportunities and barriers for rooftop greening in Australia. This paper examines green roofs in Australia, discusses the challenges to increasing their use and the major information gaps that need to be researched to progress the industry in Australia. While Wilkinson and Reed (2010) compile a unique building database incorporating information about 536 commercial buildings and evaluate the potential suitability of each building to undergo a green roof retrofit. A relatively small proportion of roofs are found to be suitable, partly a result of local climate conditions and rainfall patterns, and the physical property stock. On a purely physical assessment, only a very small proportion of central business district (CBD) stock is found to be suited. These buildings are most likely to be in low secondary locations, ungraded or B grade buildings, privately owned, concrete framed and not overshadowed by adjoining properties. Besides, compile a unique building database incorporating information about 536 commercial buildings and evaluate the potential suitability of each building to undergo a green roof retrofit. A relatively small proportion of roofs are found to be suitable, partly a result of local climate conditions and rainfall patterns, and the physical property stock. On a purely physical assessment, only a very small proportion of CBD stock is found to be suited. These buildings are most likely to be in low secondary locations, ungraded or B grade buildings, privately owned, concrete framed and not overshadowed by adjoining properties. Besides, Rowe and Getter (2006) conducted research on The Role of Extensive Green Roofs in Sustainable Development. This paper is a review of current knowledge regarding the benefits of green roofs, plant selection and culture, and barriers to their acceptance in the United States. Because of building weight restrictions and costs, shallow-substrate extensive roofs are much more common than deeper intensive roofs. Therefore, the focus of this review is primarily on extensive green roofs.
Research on environment for instance has been done by Renterghemand Botteldooren (2011) on In-situ measurements of sound propagating over extensive green roofs. In this study, in-situ measurements of sound propagation over flat, extensive green roofs were presented in 5 case studies. These involved situations with either a single diffraction or double diffraction over green roofs. Measurements show that green roofs may lead to consistent and significant sound reduction at locations where only diffracted sound waves arrive. Among the single diffraction cases, acoustic green roof improvements exceeding 10 dB were found, over a wide frequency range. While Li et al (2010) study on Effect of green roof on ambient CO2 concentration. The study systematically 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. In a typical sunny day in summer in Hong Kong, the CO2 absorption rate of a plant in the daytime is much greater than the CO2 emission rate at night. The extent of the green roof effect is related to the condition of the plants, the position of the green roof and the ambient airflow condition. In a sunny day, a green roof may lower the CO2 concentration in the nearby region as much as 2%. On the other hand, Carter and Keeler (2008) conducted research on Life-cycle cost–benefit analysis of extensive vegetated roof systems. This study uses data collected from an experimental green roof plot to develop a benefit cost analysis (BCA) for the life cycle of extensive (thin layer) green roof systems in an urban watershed. The results from this analysis are compared with a traditional roofing scenario. The net present value (NPV) of this type of green roof currently ranges from 10% to 14% more expensive than its conventional counterpart. A reduction of 20% in green roof construction cost would make the social NPV of the practice less than traditional roof NPV. Besides, Jones and Alexandri (2008) studied on Temperature decreases in an urban canyon due to green walls and green roofs in diverse climates. From this quantitative research, it has been shown that there is an important potential of lowering urban temperatures when the building envelope is covered with vegetation. Air temperature decreases at roof level can reach up to 26.0 1C maximum and 12.8 1C day-time average (Riyadh), while inside the canyon decreases reach up to 11.3 1C maximum and 9.1 1C daytime average, again for hot and arid Riyadh. It can be concluded that the hotter and drier a climate is, the greater the effect of vegetation on urban temperatures.
Research on energy and building that has been done by Chang et al (2011) on Optimal Design for Water Conservation and Energy Savings Using Green Roofs in a Green Building under Mixed Uncertainties. The study identifies the optimal green roof area that keeps within the cost of a conventional home over a specific life time, such as 50 years. Research findings show that as the reliability level associated with the chance constraint was decreased, the upper bound of the green roof area did not vary much for either shingle or metal roofs. The lower bound was found to decrease in the same situation, however, due to the higher minimum cost of the cistern in relation to the greater volume of expected rainfall, forcing the required green roof area to decrease. While Fioretti et al (2010) investigate Green roof energy and water related performance in the Mediterranean climate. The investigation performed within the specific climatic context of the Mediterranean region. Full-scale experimental results are provided from two case studies, located in north-west and central Italy, consisting in two fully monitored green roofs on top of public buildings. The attenuation of solar radiation through the vegetation layer is evaluated as well as the thermal insulation performance of the green roof structure. The daily heat flow through the roof surface is quantified showing that the green roof outperforms the reference roof, therefore reducing the daily energy demand. As for water management, it is confirmed that green roofs significantly mitigate storm water runoff generation even in a Mediterranean climate in terms of runoff volume reduction, peak attenuation and increase of concentration time, although reduced performance could be observed during high precipitation periods. Besides, Castleton et al (2010) conducted a research on Green roofs; building energy savings and the potential for retrofit. This paper reviews the current literature and highlights the situations in which the greatest building energy savings can be made. Older buildings with poor existing insulation are deemed to benefit most from a green roof as current building regulations require such high levels of insulation that green roofs are seen to hardly affect annual building energy consumption. As over half of the existing UK building stock was built before any roof insulation was required, it is older buildings that will benefit most from green roofs. The case for retrofitting existing buildings is therefore reviewed and it is found there is strong potential for green roof retrofit in the UK.
Research on perception has been done by Wan Zuriea et al (2010) on Perception towards green roof in Malaysia. Results from interviews showed that the respondents’ perceived green roofs benefits are that they provide leisure and operational space, visual amenities value and health and therapeutic value and environment and economic advantages. From the field observation study, it was found that there is a good potential for green roof as it promotes a range of benefits that can solve the problem of ecological steps, limitation of space, greenery balance, global warming, aesthetics and lost of wildlife habitat that occur in many urban areas. While House (2009) conducted research on North Texas Stakeholders: Perceptions of Extensive Green Roofs. The findings of the paper indicate thatstakeholders perceived extensive green roofs as being appropriate for use in North Texas. Concerns were raised regarding plant selection, weight requirements, initial cost, city codes, and aesthetics. Developers and city officials indicated their concern for the performance of green roofs in the extremes of the North Texas climate, while architects and landscape architects spoke of the multitude of benefits and appropriateness for this region. Overall, perceptions of extensive green roofs were favorable, but a lack of adequate research and concerns over cost issues were frequently cited as barriers to implementation.
However, in this paper, researcher tends to focus on design guidelines of green roof system. There is no similar thorough research which has been done by any other researcher in Malaysia regarding on design guideline of green roof systems. Malaysia still do not have the design guidelines for green roof system based on the preliminary interview that has been done with Encik Ishamuddin bin Mazlan from the Ministry of Energy, Green Technology and Water (KeTTHA). For instance, Hui (2010) has develop 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. The current knowledge and latest trends of green roof technology in the world have been studied. Useful information and experience were examined for assessing the potential benefits and key design factors. By investigating the system components and practical considerations of typical green roof projects in Hong Kong and other countries, key information is established for preparing the technical guidelines. Based on the review of the previous related to the research, there seems no study that has been done on design guideline for green roof systems in Malaysia and this will be an interesting topic for researcher in this Master research. Therefore, there is a gap that has been left for researcher to fill in and to contribute to the existing body of knowledge.
AIM AND OBJECTIVE
Generally, this research seeks to have an understanding and knowledge on green roof systems. This 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:
To identify the operational performance benefits of green roof technology
To explore the obstacle to adopt green roof technology
To develop design guidelines for green roof systems in Malaysia
Research questions are framed as a guide to fulfil the research objectives. This research is expected to produce design guidelines that make best use of the potential of green roof. Having decided that, the following research questions are addressed and framed
What are the effect of the green roof to the environment
How green roof can reduce energy consumption in buildings
How importance of using green roof technology in buildings
What are the obstacles in adopting green roof systems in Malaysia
How do this obstacles effect the adoption of green roof in Malaysia
What are the factor need to be considered in designing the green roof systems
The methodology in conducting is three different stages as follows:
Literature Search & Review
Literature search will conducted to gather information about green roof in order to identify the benefits of green roof systems. The sources and information from journals, articles, books and internet are then fully analyzed and studied to gain better understanding on green roof technology.
Survey will be conducted among three target populations, namely developers, architects and landscape 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 by comparison of answers to the same set of questions. The analysis of data from the questionnaires responses may provide data from which tables of obstacles can be produced.
The Case Studies combine different methods to compile an understanding of modular green roof systems. Case study methods involve an in-depth, longitudinal examination of a single instance or event: a case. They provide a systematic way of looking at events, collecting data, analyzing information, and reporting the results. As a result the researcher may gain a sharpened understanding of why the instance happened as it did, and what might become important to look at more extensively in future research.
SIGNIFICANT OF RESEARCH
This research is expected to identify the performance benefits of green roof systems in order for green roof to be utilized 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. On top of that, this research hopes to give a better understanding and way to adopt green roof systems in Malaysian buildings. At the end of this research, it will develop new design guidelines for sustainable green roof systems in Malaysia.
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