Thermal performance optimization and experimental evaluation of vacuum-glazed windows manufactured via the in-vacuum method

Abstract

Windows are essential in buildings; however, they have poor thermal performance, so extensive research has been conducted on improving their performance. In this study, we developed vacuum-glazed windows with excellent insulation via the in-vacuum method, which shortens the manufacturing time and vacuuming degree considerably. In addition, the configuration of the pillars, low-emissivity (low-e) coating, and frame from a thermal performance perspective was experimentally optimized. The results revealed that the optimal pillar placement spacing is 40 mm and that the low-e coating surface must be located inside the vacuum layer to maximize insulation performance. The vacuum-glazed window produced by the in-vacuum method was applied to an actual residential building to investigate its thermal performance, which was compared with that of a triple-glazed window. The results showed that the center-of-glazing heat flow of the vacuum-glazed window was approximately 0.8 W/m2K lower than that of the triple-glazed window. The difference between the average indoor and outdoor surface temperatures during the nighttime was found to be up to 35.1 ◦C for the vacuum-glazed window and 23.1 ◦C for the triple-glazed window. Therefore, the energy efficiency of the building can be greatly improved by applying vacuum windows manufactured via the in-vacuum method and optimized for the best thermal performance.