Cenk Kocer

The Vacuum Insulated Glass (VIG) is a highly thermally insulating device. Currently, there are commercial products that can reach a thermal conductance value, air-to-air, center-of-glass, of about 0.35 W m-2 K-1. Even though such performance in a building window would save a significant amount in energy use per year, the overall energy embodiment must be considered to quantify better the total energy saving outcomes of the VIG technology. This paper presents an input-output based life cycle analysis of the VIG technology. Taking into consideration all the upstream and downstream contributions in raw materials, production equipment, production steps, labor, transport, etc., the energy savings and embodiment are calculated. A sensitivity analysis of the production process is also provided to understand better the dominant contributions. Finally, a total impact on the return point of the technology is addressed.

The Vacuum Insulated Glass (VIG) device consists of two panes of glass, hermetically sealed around the perimeter. An array of spacer elements (well-known as pillars) is placed between the glass panes, to maintain separation under atmospheric pressure. These pillars are typically 0.5 mm in size, and can be of various shapes. The pillars strongly contribute to heat flow since each pillar is a thermal bridge. Furthermore, due to their small size, the contact pressure on the glass can be quite high because of atmospheric and other external loads. This paper presents the known processes that dictate the thermal and mechanical outcomes of pillars, with respect to their size, shape, and the underlying material they are made from. Analytical formulas are presented to provide a means to determine, with reasonable accuracy, their overall impact on the design outcomes of a VIG unit. It is found that there is a performance balance between the required thermal resistance and the mechanical strength. A complete design process for the VIG is detailed considering the pillar performance.