VIG Technology Could Allow for Greater Window-to-Wall Ratio

While vacuum insulating glazing (VIG) is relatively new in the United States, what's driving the technology is the increased performance requirements in the building codes, says Dave Cooper, advanced insulating glass (IG) program leader at Guardian Industries of Auburn Hills, Mich., and president of the Insulating Glass Manufacturers Alliance (IGMA) of Ottawa, Ontario. Use of VIG would allow for greater window-to-wall ratio, so it's in the best interest of the glass industry to develop and use such a technology, he says.

Nippon Sheet Glass of Japan has been producing VIG for six years now. "VIG is accepted and sold routinely in Japan," Cooper says. "There are some logistic issues in bringing that to the [United States], but Pilkington does sell the NSG Spacia VIG product in the States. There have been tens of thousands of VIGs produced, bought and installed throughout the Pacific Rim. So, it's not like a technology that's not been accepted."

The U.S. IG industry is looking into making VIG more mainstream. The newly formed Emerging Technology and Innovation Committee of IGMA formed a task group on VIG that

As a first step, the group will develop a white paper on what's VIG, describe the technology, define some of the acronyms and words associated with the technology, Cooper says. It should be done in the next one year, between January and March 2013. Following that the task group will start looking at creating a test standard for VIG.

"There is a VIG standard from China that doesn't include testing," Cooper says. "So, it's more like a specification, not a standard. [Next] windload tables will have to be developed for VIG. Nothing exists. Information also will have to be acquired based on impact studies on how VIG would perform in hurricanes and other natural disasters. We don't have any studies around that."

VIG started in Australia in the Solar Energy Research Group at the University of Sydney under Professor Richard Collins about 20 years ago, Cooper says. NSG is licensed under that technology to produce the IG. The major places of development are in the United States and Germany, he says. However, Europe also doesn't have any VIG standards.

There are two companies in China involved with VIG, one of which has limited commercial production, Cooper says. "There's a consortium in Europe, Pro VIG, led by Grenzebach [in Germany]," he says.

Primarily two manufacturers, QH Glass in Qingdao, China, and NSG, produce VIG. Several other companies have prototypes, such as Guardian, EverSealed Windows Inc. in Evergreen, Colo., and Grenzebach. Guardian's looking at commercializing its product in the near future, Cooper says.

VIGs are best used in sloped glazing and in extreme climatic conditions. "In vertical IGs there's a certain thermal performance based on standard convection," Cooper says. "When that's sloped, the convection within the IG is degraded. So, with sloped glazing VIG is a good choice. And in extreme conditions, you pick up some thermal performance with the added cavity and glass, and also reduce the thermal differential load per glass plate."

Various forms of VIG may include hybrids, where the VIG is used with a conventional spacer and sealant system, and super windows that consist of engineering technologies such as electrochromic or thermochromic coupled with VIG, Cooper says.