Determination of optimum insulation and cement plaster thickness for bungalow buildings through a simulation-statistical approach using response surface methodology

Insulating interior side of external wall and finishing by cement plaster is one of the most appropriate methods of reducing annual energy consumption in available buildings. The aim of this study is to determine the optimum expanded polystyrene (EPS) and cement plaster thickness for bungalow building in Malaysia. The present study evaluates the effect of different thermal insulation and interior cement plaster thicknesses on the annual cooling energy consumption. Furthermore, the optimum thickness of EPS and plaster is estimated based on wall type and building orientation. Two different types of walls made of concrete and brick are considered. EPS and plaster were used in the range of 20 to 100 mm and 0 to 20mm, respectively. The results show that both thermal insulation and plaster thickness have a direct effect on annual cooling energy consumption, however, the influence of wall thermal insulation thickness is more significant than cement plaster thickness. Further, the optimum EPS thickness decreases with the increment in cement plaster thickness for different orientations and wall types. The optimum EPS thickness ranges from 31.5 mm to 53.1 mm based on wall type, orientation and cement plaster thickness. Utilizing optimum EPS and cement plaster thicknesses can thus reduce annual energy consumption by about 6 to 12% in different directions.