Researchers at Guardian Industries have recently unveiled a new breed of vacuum-glazed super glass with an incredible R12-R13 insulation rating. For those of you who know nothing about R-value (the standard construction measurement of how insulating a material is), this is an incredible insulation value for glass. Typical insulation brick and plaster walls usually have an R12 rating, and glass usually gets a R1 or R2. That means this new vacuum glass is as insulative as a thick insulated wall. Using the same principle as a vacuum thermos bottle, these glass panels essentially negate two principal modes of heat transfer, paving the way towards windows that actually supply thermal energy instead of leaking it.
Take a look at any of the latest silver, gold, and platinum LEED superstructures and you’ll see a striking visual metaphor at play. As paragons of sustainable architecture they literally shine, sparkling with the glossy grandeur of glass encrusted façades. Now consider the fact that “Windows in the U.S. consume 30 percent of building heating and cooling energy, representing an annual impact of 4.1 quadrillion BTU of primary energy” ¹. In order to make these towers work, insulated glass is used, but it’s expensive, heavy, and requires triple glazing and multiple low emissivity coatings.
Using the same principle as a vacuum thermos bottle, researchers at Guardian industries have created a thin .25mm space between two sheets of glass that is vacuum-sealed to 10–4 torr. This vacuum mitigates the two principal modes of heat transfer – conduction and convection, while a ClimaGuard low-E coating polishes the panel off, significantly reducing heat loss via radiation. The glass panels are marvelously thin, at .26 to .43 inches, and can be reinforced for an added R1-R5 insulation value.
Stephen Selkowitz (an author of the above cited study) has lauded the development, stating: “This performance level would convert most windows in heating climates into net energy suppliers, providing more energy to the home via passive solar gain than the window loses”.
Guardian hopes to roll out these new vacuum-sealed vitrines in 2009.
¹ Steve Selkowitz, Dariush Arasteh, Josh Apte, Marc LaFrance, “Zero Energy Windows”, EETD Conference, 2006. p. 1.