Vacuum insulating glass (VIG) is a high-performance glazing product that can provide increased occupant comport and reduced U-values. However, the technology is still fairly new to the U.S. market. In a webinar titled “How to Design for Sustainable Buildings with Vacuum Insulated Glass,” Tim Cope, chief technology advisor for Guardian Glass, and Andrew Kreifels, strategy business development manager for Guardian Glass, explained what VIG is, how it works and its overall benefits.
What is VIG?
It’s been 30 years since the first VIG was created in 1989. A lot of progress has been made since then in temperable glass, coatings and edge seal technology, according to Cope. VIG consists of two glass lites, pillars to keep the glass separated, an evaporable getter that absorbs gasses and other materials to maintain the vacuum, edge seal materials and an evacuation port that allows the manufacturer to evacuate air from between the glass lites.
The vacuum gap between the lites varies from manufacturer to manufacturer, but on average is 0.3 mm. The glass lites range in thicknesses of 3-4 mm.
Cope explained that in a vacuum, there are very few molecules, resulting in dramatically reduced energy transfer between the two lites in a unit. However, he pointed out that the pillars do transfer heat.
“This gives a roadmap for future improvements. As pillar spacing and design changes, the limitation for VIG is almost limitless,” he said. “If the pillars didn’t need to be there we could reach R-values as high as 60. It gives us something to shoot for in the future.”
Benefits of VIG
VIG’s performance combined with its thin construction makes it ideal for renovations or retrofit applications where a glazing system needs to fit into an existent glazing pocket.
Kreifels gave an overview of the different design criteria for high-performance building, which include thermal separation, daylight and views, occupant comfort and sustainability, as well as codes and incentives.
VIG has benefits in each of these categories, according to Kreifels. Cope said that VIG allows the architectural community to go further with the window-to-wall ratio and limit tradeoffs due to its high performance. VIG also improves thermal comfort because the vacuum does not transfer as much heat as air or argon in double pane or insulating glass units, respectfully.
Vacuums also have sound reduction properties, allowing VIG to achieve similar sound reduction performance as laminated configurations.
Kreifels explained that VIG can create a 30-60% reduction in operating carbon emissions, which is the carbon emitted from a building during its operation. He said it’s still unclear how VIG impacts embodied carbon, which is the carbon emitted during the manufacturing and construction of a building and its materials.
As far as codes are concerned, Kreifels said that many wonder if codes will push the industry toward VIG.
“The short answer is no,” he said, noting that U-factors are coming down over time but that model codes, by mandate, cannot force a really aggressive target into the code. This is because a product has to be readily available by multiple suppliers, have adequate competition and lower prices. However, local codes can impose aggressive regulations.
Kreifels also answered some common questions. He said that the current availability of supply is limited and that it’s important to make sure that the product is certified. He also explained that while the pillars and vacuum port are visible, they are not very noticeable. He anticipates that transparent or translucent pillars will be developed in the future.
The webinar was hosted by Building Enclosure and sponsored by Guardian Glass.