Pushing Performance: How VIG is Defining Energy Efficiency

By Jordan Scott

Vacuum insulating glass (VIG) isn’t new, but awareness of the technology is still growing within the U.S. VIG technology is being pushed to help meet the potential for tough energy codes globally due to its thinness and energy efficiency.

Using thick glass, such as approximately 5/16- or 3/9-inch (8- or 8.5-mm) glass for VIG creates higher energy performance and a lower U-factor compared to using approximately 1/8-inch (3-mm) thick glass for VIG. According to Kyle Sword, business development manager at Pilkington North America of Toledo, Ohio, thicker glass is more rigid which means it’s stronger and provides greater wind resistance so it can be used in larger sized units.

While thicker glass in VIG units provides higher energy performance, Sword says there are several benefits of using thin glass for VIG as well. One benefit is that thin glass weighs less.

“Thicker glass increases the weight by 33 percent. If you scale that up to the entire size of the building it’s a lot heavier,” says Sword.

According to Martin Bracamonte, president and COO of VIG Technologies in Jupiter, Fla., VIG can achieve an R-value that’s four-times better than standard IG units.

“This is not an incremental improvement,” he says.

VIGs are also less likely to be impacted by the effects of gravity, so their energy performance remains the same if horizontal, which is important for applications such as skylights.

Michael Spellman, founder of VIG Technologies, says he sees the potential
for an R-value of R10 in architectural curtainwall due to the energy efficiency
of VIG.

“This is really where the window becomes the wall,” says Spellman.

A Retrofit Solution

Thin VIGs are often an ideal solution for historic restoration and renovations
because the windows and sash were built thin in older buildings.

“The thicker you go, the thicker the sash has to be to accommodate it. For
new windows, you can often design a thick, heavy sash but then you’ve got
to adjust your counterbalances and you’ve got to use thicker plastic, vinyl
or wood,” says Sword.

Replacing single-pane glass provides much better energy efficiency, according to Greg Kemenah, director of Guardian VIG at Guardian Glass, based in Auburn Hills, Mich.

“Using Guardian Vacuum IG in commercial retrofits allows direct replacement of single-pane glass. A single pane has an R-value of R1, and replacing it with VIG takes the R-value up to 12,” he says. “This is the key benefit of using VIG. If you are replacing the window glass with a standard double unit, you have to replace the entire window, which can be very costly over the entire project.”

Guardian Glass has seen steady growth for VIG in new construction and retrofits, despite the continued perception that window upgrades have a poor return on investment (ROI).

“We’re still seeing that, even in older buildings with single pane monolithic
glass, facility managers are looking first to low-hanging fruit for energy efficiency gains. Some are staying away from the envelope because to go from single-pane monolithic glass to double-pane insulating glass and replace the windows isn’t a very good ROI story,” says Kemenah. “We enjoy explaining how VIG units solve this problem. Two fully tempered glass lites are held apart by nearly microscopic pillars and, because there is no gas between the lites, there is no medium to transfer heat … There is tremendous payback, and the added benefit of noise reduction and possibly increased daylighting.”

Sword says there is a barrier to creating even thinner VIG units. If the glass
is thinner, the vacuum pressure would pull in between the micro-spacer array that holds the glass lites apart, making it more likely to break due to higher pressure points.

Code Driven

“Building codes are just going to get tougher, forcing architects and facility managers to carefully evaluate options for new construction and retrofits. Getting the best window assemblies possible for a facility is a means to future-proof the envelope by adding value to the building, increasing the thermal comfort and visual comfort of the people inside,” says Kemenah.

Sword says that the new energy standard proposals in Canada for 2025 and
beyond required a U-factor so low that he doesn’t know if it’s achievable with
double glazing or even triple glazing.

“People can do it with quads and by adding more glass and krypton, but at
a certain level of performance it looks like VIG will have to be used at some
point,” he says.

In Japan, Pilkington has seen demand for hybrid VIG units where the standard double-glazed unit is altered by replacing one of the glass lites with a VIG.

“That gives you a triple-glazed performance with double-glazed thickness,” says Sword.

Guardian Glass offers a VIG hybrid that includes its SunGuard coated glass
on surfaces No. 2 and No. 4 to boost the R-value up to R14.6.

Bracamonte expects manufacturing of VIG in North America to grow rapidly, especially driven by the Canadian codes and early adopters in the U.S.

“The glass industry runs on codes. If not the industry will be resistant to
adopt new technologies, but I see the change coming,” he says.

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