Window is a critical component in the design of energy efficient buildings. To increase the energy efficiency of a building by minimizing the heat loss, insulation performance of glazing has to be improved. Manufacturing of vacuum glazing has been motivated by the possibility of making windows of very good thermal insulating properties for such applications. Vacuum glazing is made by maintaining vacuum in the gap between glass panes. Pillars are placed between them to withstand the atmospheric pressure. To reduce conduction through the edge, edge covers are applied. Accurate measurements have been made of the radiative heat transfer, the pillar conduction and the gas conduction using a guarded hot plate apparatus.
Vacuum glazing is found to have low thermal conductance roughly below 1 W/$m^2$K. Among the heat transfer modes of residual gas conduction, conduction through support pillar and radiation, the radiative heat transfer between the glass panes is dominant to the overall thermal conductance. Vacuum glazing using very low emittance Al-coated glass has an overall thermal conductance of about 0.7W/$m^2$K. Vacuum glazing can be applied not only to buildings but also to many digital appliances thanks to the small thickness and good insulation performance.