The projected annual cooling load and energy savings revealed that the application of a 20-mm cement render, coupled with the installation of a 100-mm thick insulation board, is recommended as the optimum roof configuration. For optimization of thermal and strength performances, silica aerogel contents of 4 wt.% and 3 wt.% were selected for the cement render and insulation board, respectively. A simulation study was performed on a Building Information Model subjected to a tropical climate to project the resultant impact of the cement render coupled with the insulation board on the thermal-energy-efficiency of the roof. Thermal conductivity and strength tests were performed on the samples. Control and silica-aerogel-incorporated samples of the composite cement paste and insulation were prepared. In the present study, the application of silica-aerogel-incorporated composite cement paste as render on the roof-top surface is coupled with the installation of a novel silica-aerogel-incorporated composite insulation board below the roof tiles. Owing to the fragility of monolithic aerogel, the development and production of aerogel-based insulation materials involve the incorporation of granular aerogel with other materials to form composite materials. Silica aerogel possesses an ultra-low thermal conductivity by virtue of its nano-structure. The simulation projected that the application of white paint on high-albedo roof tiles can generate annual energy savings of 13.14 % and, when adopted in amalgamation with the installation of bulk rafter insulation within the roof assembly, 13.91 %. Evaluation of thermal-energy performance was performed on a Building Information Model, which either adopts, solely, the application of white paint on high-albedo roof tiles, or, in amalgamation with, the installation of bulk rafter insulation within the roof assembly. Hence, thermal-energy performances of high-albedo roof tiles and bulk rafter insulation were compared to develop an energy-efficient pitched residential roof assembly that is capable of minimizing diurnal heat transfer into the building with less obstruction of the nocturnal heat transfer in the opposite direction. However, their adoption will have an influence on the nocturnal heat transfer and, accordingly, the resultant thermal-energy performance.
Diurnal heat transfer into the building through the roof assembly can be minimized by reflecting heat at the roof surface via the application of white paint on high-albedo roof tiles as well as resisting heat via installation of bulk rafter insulation within the roof assembly. Residential buildings typically employ a lightweight pitched roof with roof tiles and an attic space above a ceiling board. Residential roof assemblies in tropical countries, such as Malaysia, are exposed to intense solar radiation throughout the day all-year round due to the high altitude of the sun path as well as the horizontal orientation and high position of the roof in relation to other components of the building envelope.
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