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The ever-increasing temperature of current climate has brought the attention on reducing the incoming solar heat energy into buildings. The efforts on reducing the dependency on air-conditioning for indoor cooling has led to the implementation of passive cooling strategies in buildings. This paper investigates the implementation of reflective technologies in the form of reflective insulation and radiant barrier systems in a gable roof assembly. The thermal performance of reflective insulation and radiant barrier systems was investigated by using Computational Fluid Dynamics (CFD) simulation. The thermal performance of the reflective technologies was presented in terms of thermal resistivity, RSI value. The study was conducted for several roof configurations where the thickness of reflective air space, roof pitch and the roof material were varied. The results obtained from the CFD simulation was validated against empirical measurements to ensure the simulation gives high accuracy prediction. From the parametric analysis, it was found that thicker reflective air space would provide better air ventilation in the air space area which led to higher thermal resistivity. Besides that, steeper roof pitch would enhance the buoyancy effect and increases the heat exhaustion through the ridge which also results in higher thermal resistivity. In terms of roof tiles material, only small difference was observed in terms of thermal resistivity when switching the roof tiles material between clay tiles and concrete tiles. This research was able to demonstrate the use of CFD simulation in investigating thermal insulation technologies in buildings and this method should be explored further in the future.

The trend in building energy consumption has been steadily increasing and will continue to rise significantly in the future. The application of a reflective insulation system in roof assembly is proven to be effective in reducing heat gain across the roof and can enhance indoor thermal comfort. This paper presents the development of an Indoor Solar Simulator to evaluate the thermal resistance (RSI value) of reflective insulation systems for roof assemblies. This paper also compares RSI values obtained experimentally and the RSI values listed in ASHRAE Standard. The roof assemblies studied in this paper incorporate the same reflective insulation systems as listed in ASHRAE Standard. Thermocouples and heat flux transducers are installed at various locations and the RSI values are calculated using the average method as detailed in ISO 9869-1:2014. From the error analysis, it can be concluded the RSI values obtained experimentally using the Indoor Solar Simulator and ASHRAE Standard are in a good agreement with MAPE value of 6.13%. These discrepancies could be due to the thermal bridges from mechanical supports inside the air gap, or possibly the air gaps are not completely airtight and unventilated.