Vacuum Insulation Glazing
Improving the thermal insulation of commercial buildings has an important role in tackling increasing energy demand and CO2 emissions. Reducing the heat transfer through the building fenestration has a big impact: often more than 60% of the heat is lost or gained through windows, which show a very high heat transfer (U-value ~0.8 W.K-1.m-2) compared to other building envelopment elements such as roofs or walls. Current solutions to reduce the U-value display a variety of problems, such as reduced light income or high weight, which are limiting their widespread adoption.
Compared to conventional glazing, VIGs potentially offer a much improved thermal performance (U-value ~0.3-0.5 W.K-1.m-2) and substantial reduction in weight as just two glass panes are needed. The edge sealing constitutes the main technical challenges for the wide uptake of VIGs: a rigid edge seal limits the size and thermal performance of the VIG as the differential thermal expansion of the inner and outer pane can cause the glazing units to break. As part of the European Winsmart Consortium (winsmart.eu), the Superinsulation Materials Group develops novel edge sealing technology for the production of VIGs. The flexible Winsmart edge seal consists of two laser welded metal ribbons that can accommodate the differential thermal expansion between inner and outer pane. At Empa, we use our patented technology for liquid solder anodic bonding to bond metal ribbons to glass (Koebel et al. 2011 , El Hawi et al. 2013, Elrefaey et al. 2014). Prototyping at the 0.5x0.5 m2 scale has been completed and we are currently developing 1x1 m2 prototypes.