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Silica aerogel has attracted increasing interest in building glazing for energy efficiency owing to its light weight, ultra-low thermal conductivity and high visual transmittance. In this study, four types of aerogel granules with various average particle sizes (viz. 0.41, 1.03, 1.64 and 2.54 mm) were prepared by using a low-cost ambient pressure drying method. Three gaps between two pieces of glass (viz. 6, 9 and 12mm) were filled with aerogel granules, yielding 12 pieces of aerogel filling glazing. The light transmittance and reflectance of the aerogel glazing samples were experimentally measured by using a spectrometer. Based on the experimental results, the correlation between the light transmittance performance and the geometrical parameter of the aerogel glazing were established based on a proposed dimensionless geometrical parameter. It revealed that the visible light transmittance and the shading coefficient of the aerogel glazing had a positive correlation with the particle size and a negative correlation with the filling thickness. In addition, the filling thickness had a greater influence on the properties of aerogel glazing than the particle size. This opens new possibility for a multiple-objective evaluation of the aerogel glazing aiming at building energy efficiency.

Aerogel glazing units (AGUs) is a high-performance building glazing which can effectively reduce energy consumption due to its thermal and optical performance. In this paper, the effect on thermal and optical properties of AGUs with different particle sizes and filling thicknesses were investigated. The results indicated that visible light transmittance and solar direct transmittance of AGUs palpably increased as the particle size increased from 0.41mm to 0.93mm, while it lightly changed as the particle size continued to increase from 0.93mm. The heat transfer coefficient decreased by about 15% when the particle size was reduced from 2.7mm to 0.41mm. In conclusion, the increase of the thickness of aerogel can effectively decrease visible light transmittance, solar direct transmittance and heat transfer coefficient. Finally, color rendering index(CRI)the AGUs with different particle sizes and filling thicknesses were investigated and AGUs show good color performance.