The effect of long term exposure on thermal performance of roofing materials in Malaysian climatic condition

Abstract

Owing to exponential increase in world population and high influx of migrants to urban areas, demand for space in form of housing and infrastructure has increased in most urban centers yielding a high number of infrastructural developments requiring clearing of vegetative land cover and replacement by roofs and paved surfaces. The materials used in most cases have higher absorptive heat capacities than the soil and vegetation they replace resulting in the phenomenon known as Urban Heat Island (UHI) where urban areas are hotter than their surrounding rural areas. In tropical regions where solar radiation intensities are higher and rainfall is all year round, thermal performance of these materials is altered by the climatic conditions. The growing population and rising demand for infrastructure calls for careful evaluation of materials used in the urban fabric as a strategy for the mitigation of the UHI phenomenon. This study was carried out on commonly used roofing materials in Malaysian tropical climate; clay and concrete roof tiles adopting two methodologies for the samples. Full scale testing for concrete tiles measured between 12- 19th April, 2011 and exposure rack method for clay tiles measured 1st- 8th July, 2011. Surface and ambient temperature measurements were taken for seven days each by HOBO U-12 Data loggers on samples which had been exposed for varying durations of above 25years, 15years, 10years and less than one year. Climatic conditions such as relative humidity, air temperature and wind speed were recorded using the Environ Data weather station set- up on the study site of the UTM campus. Analysis was made using measures of descriptive analysis on Microsoft Excel and independent paired sample t-tests were carried out on SPSS software. Results showed that after over 25 years of exposure, maximum surface temperature of concrete tile dropped by 12% while the clay rose by 3.68%. Minimum surface temperature of concrete rose by about 2% and no significant changes were observed in the clay tile at night. Thermal performance evaluation of materials used in the urban fabric is essential as a passive solution to mitigating the negative effects of UHI.