The Vacuum Insulated Glazing (VIG) is a thin, light weight, highly thermally insulating window technology that has now a commercial lifetime of over 20 years. Much of the performance of the VIG has been well documented in the scientific literature. Nevertheless, in the last decade it has become clear that the thermo-mechanical performance of the VIG as a complete window structure in a building envelope requires further attention. VIG design changes, U-value requirements, and the structural variety in building construction, means that defining the constraints within which to examine the VIG performance is not a trivial matter. It is the purpose of this talk to define the fundamental properties of the VIG device and that of the faming element within the building envelope, from which results of thermal load scenarios are presented and discussed. It is found that there is a clear difference in the VIG application, relative to the existing gas filled technology. A novel frame design optimisation is presented and shown to provide a complete window application that well suits the future thermos-mechanical requirements of the building stock.