Recent progress in the development of windows with vacuum glass

This contribution reports on recent advances in the utilization of vacuum glass in contemporary window construction. Generally speaking, vacuum glazing consists of two glass panes with an evacuated interstitial space. To maintain the functionality of the glazing, a vacuum-tight edge seal and a grid of distance-holding pillars are required. Vacuum glazing features a first-rate thermal performance as it significantly reduces conductive and convective heat transport rates. In comparison to multi-pane insulation glasses of comparable thermal performance, vacuum glass products feature a reduced weight and construction depth. However, the application of vacuum glass in windows requires a critical rethinking of the current practice of window construction, especially with regard to thermal bridges and the related surface condensation risk at the glass/frame-construction joints. Specifically, the glass edge seal, which can be considered to be the weak spot of vacuum glass in terms of heat transfer, requires an insulating cover that is not provided in typical insulation glass frame configurations. Further relevant aspects to be considered include the structural stability of window constructions with vacuum glass, the acoustical performance, and issues regarding usability. In this context, the present contribution highlights the methodology and findings of two recent research projects (MOTIVE, FIVA) that addressed window construction requirements with regard to vacuum glazing deployment.