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  • br Reflective roof strategy slowing down the

    2018-10-22


    Reflective roof strategy (slowing down the heat transfer into a building) Studies estimate that about 60% of urban areas are covered by roofs and pavements (Akbari et al., 2008). This figure continues to increase, given that 50% of the world׳s population are currently found in urban regions. This figure is expected to increase to 70% by the end of 2040. Such an increase has been clearly reflected in the behaviour of UHI. Wong et al. (2011) showed that the heat island intensity may increase by up to 10°C, as had happened in India. As shown in Figure 4, the effect of urban development in Singapore is reflected by the quality of the city environment. De Koninck et al. (2008) reported that the surface air temperature of urban areas is very high, reaching up to 40–50°C. Priyadarsini et al. (2008) showed that downtown areas maintain their temperature at midnight, with the air temperature reaching as high as 28.5°C. In contrast, other places in rural areas, whose air temperature reach below 4°C, as shown in Figure 4(b). Wong et al. (2011) suggested that the UHI in Singapore indicates a potential increase of urban air temperature by 1°C. Tso (1994) showed that if such trend continues, the purchase CMX001 consumption required to cool down the whole island will increase by 33GWh per year within 50 years. With a population of over 238 million, Indonesia is the world׳s fourth most populous country. This country consists of 34 provinces, with Bandung, the capital of the province of West Java, as the second largest metropolitan area. The urban areas of Bandung significantly suffer from high urban density, as shown in Figure 5. Tursilowati (2007) suggested that the surface temperature of the city will tremendously increase in less than ten years because of the construction of more roofs and pavements that come along with urban expansion. The colour of external surfaces (such that of the roof) has a remarkable counter-effect on the impact of solar radiation on buildings and the indoor temperature of buildings without air-conditioning systems. This technique is widely implemented in hot regions, but its application in the tropics remains imperfect. Concerning the issue on a small scale, Al Yacouby et al. (2011) showed that the colour of the majority of roof tiles in Malaysia is dark, as shown in Table 1. In fact, this review found that not one of the developed countries in Southeast Asia employs the reflective roof strategy. In Singapore, Building & Construction Authority launched the BCA Green Mark in 2005 to encourage the construction of energy-efficient buildings. However, no specific standard provided for the use of the cool roof technology. In Malaysia, the Ministry of Energy, Green Technology and Water specified energy efficiency standards in the building code such as Green Building Index. However, this standard does not include the use of cool roofs in Malaysia. In Indonesia, the Greenship asgreen building rating system was established in 2010 to introduce a standard for green initiatives and Overall Thermal Transfer Value (OTTV) calculation. However, no specific policy measure pertained to the use of cool roofs (Building System & Diagnostics Pte Ltd., 2011). The study of Al Yacouby et al. (2011) on Malaysia showed that 27.9% of the survey respondents prefer red as the colour for the roof tiles of their new houses, 19.6% brown, 19.2% blue, 11.1% green, 9.6% grey, and 4.8% yellow. However, 68.8% of the respondents did not object to changing the colour of their tiles to white, if only to reduce the costs of air conditioning. Given this incipient interest on reflective roofing, this approach should be fully explained to both occupants and designers. Givoni (1994) has been studying the effect of the colour of roofs since 1968 at the Technion in Haifa. His first study revealed that lightweight roofs made of a type of concrete called Ytong, which is 7, 12 and 20cm thick and painted grey, investigated with a maximum external air temperature of approximately 31°C, generate an average maximum external surface temperature of about 69°C. The maximum ceiling temperatures are likewise significantly affected by the thickness of the roof: 45°C, 39°C, and 33°C, respectively. Conversely, when the roof was painted white and investigated with maximum air temperature about 27°C, the average external maximum surface temperature was about 27.5°C. The maximum temperature of the ceiling was about 25.5°C for all roofs.