In this prototype vacuum-insulated glazing panel, the pillars holding the panes of glass apart (the dots) are readily visible due to the low viewing angle. (The grid visible on the glass is a reflection of ceiling tiles.)
Guardian Industries, one of the world’s largest architectural and automotive glass manufacturers, with 19,000 employees in 25 countries, has under development a revolutionary vacuum-glazing panel that provides a center-of-glass insulating value of R-12 to R-13. The glass—Guardian VIG (for vacuum-insulated glass)—has a very thin (250-micron or 0.25-mm) space evacuated to 10–4
torr (for reference, thermos bottles typically have a much harder vacuum of around 10–6
torr) between two layers of glass, one of which has a low-emissivity (low-e) coating. Guardian is currently producing the vacuum glazing on a limited basis for testing and hopes to roll it out commercially by the end of 2009.
Heat travels in three modes, and the vacuum effectively eliminates two of them: conduction and convection. But the vacuum doesn’t eliminate radiation, so the low-e coating is critical to the unit’s performance, according to Scott Thomsen, the chief technology officer and group vice president of Guardian’s Science and Technology Center. The type of low-e coating also has a huge effect: a hard-coat (pyrolytic) coating yields only R-2 to R-3 insulation, and standard low-e coating yields R-4, Thomsen told
. To achieve R-12, Guardian uses its more advanced ClimaGuard Low-E glass, which has two deposited metallic layers like Cardinal’s LoE2
. Energy performance testing of the Guardian VIG panels has been done at the University of Waterloo in Ontario.