Improving the thermal insulation of glazing units is a common strategy of reducing building energy use for spacing cooling. This paper newly examined the application of aerogel glazing technology in Hong Kong by the means of laboratory testing and simulation. Nine prototypes of granular aerogel glazing were selected to examine their optical properties, and the measured optical properties of aerogel were used to calculate the total window thermal performance indices. A typical 40-story commercial office building was chosen for energy simulation to compare the thermal performance of aerogel glazing with different glazing technologies in Hong Kong. The results showed that aerogel glazing could achieve the promising reduction of window heat gain up to 57% and cooling energy up to 8.5% compared with double glazing. The heat insulation performance of aerogel glazing is even better than the double glazing with low-E coating in Hong Kong. Therefore, aerogel glazing can be a good alternative of glazing to comply with the existing local Overall Thermal Transfer Value (OTTV) requirement and to reduce the building energy use for space cooling in Hong Kong and other regions.