Thermal and daylighting performance of glass window using a newly developed transparent heat insulated coating

Abstract

In subtropical Hong Kong, solar heat gain through glass windows contributes to a significant proportion of building cooling load. Therefore, in cooling dominated areas, the principal of window design includes both utilizing natural daylight and eliminating solar heat gain. In this study, a new heat insulated coating combined antimony-doped tin oxide (ATO) and cesium tungsten bronze (Cs0.33WO3) was developed. Based on measured properties of different glass samples, thermal and daylighting performance of different glass windows, including a clear glass window, a double-layer glass window, a low-e glass window and a coated glass window, were evaluated based on numerical simulation. Results indicate that the developed heat insulated coating can effectively reduce the solar heat gain while maintain the indoor daylighting illuminance at a high level. Up to 9.5% of building energy use can be saved if the coating is applied to south facing clear glass windows.