Effect of facade components on energy efficiency in office buildings

Highlights: • Investigation of facade properties for energy efficiency of Tokyo office buildings. • Higher reflectance for opaque parts may slightly reduce energy demand. • Lower window U-value and solar heat gain coefficient are potential solutions. • Decreased heating due to insulation did not always compensate increased cooling. • Fundamental data for adjustment of facade properties of buildings are provided. - Abstract: Properties of facade materials should be considered to determine which of them strongly affect building energy performance, regardless of the building shapes, scales, ideal locations, and building types, and thus may be able to promote energy efficiency in buildings. In this study, the effects of four fundamental facade properties related to the energy efficiency of office buildings in Tokyo, Japan, were investigated with the purpose of reducing the heating and cooling energy demands. Some fundamental design factors such as volume and shape were also considered. It was found that the reduction in both the solar heat gain coefficient and window U-value and increase in the solar reflectance of the opaque parts are promising measures for reducing the energy demand. Conversely, the reduction in the U-value of the opaque parts decreased the heating energy demand, and this was accompanied by an increase in the cooling energy demand in some cases because the total energy demands were predominantly for cooling. The above-mentioned promising measures for reducing building energy demands are thus recommended for use, and an appropriate U-value should be applied to the opaque parts based on careful considerations. This study provides some fundamental ideas to adjust the facade properties of buildings.