I. Introduction
Large numbers of research and testing show that the solar radiation carrying much heat transmits through the external building glass and overheats the indoor space in summer mainly because of the poor thermal insulation properties of glass [1]. Especially in hot summer and warm winter zone in China where the outdoor temperature is high, the solar radiation is intense and the hours of daylight are long in summer, the research of the energy efficiency of external building glass has already become one of the critical tasks in building energy efficiency [2].