Roof angle for optimum thermal and energy performance of insulated roof

Mineral wool is among the commonly used conductive insulation material for building insulation. Studies on insulated building envelope in temperate climate have shown potential energy savings towards attaining energy efficient buildings and sustainable built environment. To date, there is no empirical data on the benefits of insulated building envelope in warm humid tropical climate. Such data would provide commercial mileage to the insulation and building industries. Hence, the Center for Research and Innovation in Sustainable Energy (RISE) of Universiti Teknologi MARA has embarked on research collaboration with a local insulation manufacturing association. This paper presents the empirical findings on thermal and energy evaluation of mineral wool insulation under Malaysian sky condition. The objectives of the study are to evaluate the whole-building thermal and energy performance for mineral wool insulation at roof pitch for selected roof pitch angle, and finally to identify the optimum roof pitch angle due to the thermal and energy saving potential. The experimental works were conducted inside the Twin Energy Efficiency Test Cells inside the campus of Universiti Teknologi MARA, Shah Alam Selangor. Two test buildings named as Test Cell A and Test Cell B has identical building design with conventional envelope constructions. Test Cell A was the control unit while Test Cell B was later modified with the installation of mineral wool insulation of thickness 75 mm at roof pitch angle of 10°, 15° and 20°. Both cells were installed with a normal 750 W split unit air-conditioning system. Identical automated outdoor and indoor data logging systems were installed inside both test cells for simultaneous data collection. For each roof pitch angle, ten days data from Test Cell A and Test Cell B were simultaneously and consecutively monitored in a 24-hour air conditioned (AC) mode. Ambient temperature for outdoor and attic were collected for the thermal performance analysis. Electrical data of current, voltage, power and energy consumption were collected and analysed for the building cooling energy performance. The thermal and energy performance of the mineral wool insulation were appraised by the cooling load savings. The findings identify the optimum roof pitch angle and conclude that the mineral wool insulation at roof pitch produces nominal thermal improvement but noteworthy energy savings.