Blog Post

R-10 Vacuum-Insulated Glazing

For real this time?

In this close-up photo of a Spacia vacuum-insulated glazing unit, the "pillars” holding the two panes of glass apart appear as white dots on a dark surface and dark dots on a light surface. The pillars only show up at certain viewing angles. About 50% of people don’t see the pillars until someone points them out.

For twenty years or so, companies like Pilkington (Spacia) have been cranking out R-5ish (center-of-glass) vacuum-insulated glazing (VIG). The attraction of glazing units with a very thin profile, relatively low weight, and a high level of performance is strong, particularly for retrofit applications.

But it sure seems as though we have been promised commercially available VIG with double that thermal performance for more than ten years now. (See this 2009 blog post by Alex Wilson.) The technological challenges for this level of performance have been significant, and so have costs.

My good friend and colleague, Charlie Curcija — senior researcher in the glazing program at Lawrence Berkeley National Lab — is the guy I always go to for the latest and greatest news on high-performance glazing. He says we very well could be there.

“The breakthroughs required for R-10+ VIG were in three areas:

  • One, producing uniformly flat tempered glass (this is important for pillars to stay where they are supposed to);
  • Two, having temperable low-e (Guardian was one of first companies, if not the first to develop temperable low-e); and
  • Three, developing a low-temperature edge sealing process, so that glass does not de-temper.”

According to Curcija, who recently returned from Asia, there are about seven or so Chinese companies that are producing VIG in the R-10+ range (center-of-glass) and just one being produced in the U.S. (by Michigan-based Guardian Glass). Guardian just did a big press event at an AIA conference for their two commercially available VIG products. And then there is Florida-based VIG Technologies, a company that uses LandGlass VIG from China.

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Vacuum-insulated glazing relies on empty space rather than a gas between the layers of glass for thermal performance.  "Getter” material is a reactive deposit or coating used to absorb or chemically react with any remaining gas inside the vacuum space of the glazing unit. 

Image: VIG Technologies.
So, we're are all set and just need to talk about pricing, right?

Are the products even available?

Not so fast; both Guardian and VIG Technologies are still very tight-mouthed about the major U.S. window manufacturers they claim to be working with. Apparently, you can’t order product from either of these VIG producers or any window manufacturers to date.

There are real VIG installations in the U.S.: VIG Technologies has units installed at Viracon headquarters in Minnesota (Viracon is the largest glazing manufacturer in the U.S.), and Guardian has some of its units installed as retrofits at Eastern Michigan University. By all reports, these units are performing really well. Curcija observed the Viracon units on a cold winter day and said that the units looked great and the thermal comfort near the units was impressive. Robert Densic, Eastern Michigan University’s manager for planning and design, is working on some initial Guardian Glass installations as a proof-of-concept project for much broader applications of  VIG products across the campus.

This chart shows the two IGU configurations that lead to R-10+ thermal performance for a VIG, in this case from Guardian Glass. Note how incredibly thin the units are (with a gap between the panes of glass just 0.3 mm and very thin tempered glass).

Image: Guardian Glass.
So what is the holdup?

A lack of industrial capacity

One trusted window industry source told me this: it’s really hard to focus on and marshal resources for new high-performance glazing when the industry is as stoked as it is right now. Charlie Boyer, vice president of research & development for Viracon, backed that up. He said, “We are very interested in this technology but we simply don’t have the capacity right now and are not quite ready to make the very substantial investment required to set up a whole new facility for VIG.”

Additionally, when I asked Guardian Glass some very pointed questions about commercialization, one of their written responses was: “The Guardian Vacuum IG team is focused on multiple industries, with commercial refrigeration leading the way. We have partnered with Anthony International, the leader in the refrigeration door industry.” Huh? Refrigerator doors?

Another trusted industry source told me this: no one in the window/glazing industry has seen any third-party-certified laboratory testing of the new VIG product using the industry standard, ASTM E2190, “Standard Specification for Insulating Glass Unit Performance and Evaluation.” This testing includes temperature extremes and accelerated aging/weathering testing.  (For more information on this standard, including descriptions of specific tests, see “Certification & Testing for Insulating Glass Units.”)

A new standard

A wall of VIG Technology units installed in a Viracon office at their headquarters. The thermal performance is reportedly outstanding. Note the high visual transmission as well. 

Image: Viracon Industries.
If you lose the vacuum seal on these IGUs, the thermal performance does not fade—it crashes.

There is a new standard being developed specifically for stress-testing VIG:  ISO/DIS 19916-1, “Glass in building—vacuum insulating glass—Part 1: Basic specification of products and evaluation methods for thermal and sound insulating performance.”

Rob Tenent of the National Renewable Energy Lab (NREL) is gearing up for a project looking into the specific stress-testing needs of VIG, working with Lawrence Berkeley National Labs (LBNL). Frankly, no one seems to know, or be willing to state, whether these new VIGs require stress testing tuned to their performance or properties. But that is exactly what this NREL/LBNL project is about.

The refrigerator door market

All of this concern could be one of the reasons that Guardian Glass is focusing on the refrigerator door market: While the temperature difference from inside to outside the refrigeration units is large, it represents a fairly steady delta-T.

I am not saying that the VIG seals or long-term performance are suspect; I am saying that no one seems to know or be willing to talk openly on this issue, and it is really important.

How much do these IGUs cost?

A variety of Guardian Glass VIG units have been installed at Eastern Michigan University (EMU) as part of retrofit projects of existing building (in and around December 2017). Thermal performance studies of these units are being conducted. Faculty and students report better thermal comfort and acoustics with the VIG units. 

Image: Robert Densic, EMU.
What about costs? Not surprisingly, it’s impossible to get this sort of information from VIG Technologies or Guardian Glass at this point. But here is what Curcija learned while in Asia: Chinese VIG producers gave manufacturing costs of up to 1,500 Yuan/m2. Using $1 = 6.7 yuan and roughly 10 sf/m2, that equates to $22 per square foot. In the U.S., it’s typical to multiply manufacturing cost by three to get the consumer price (glazing installed in a window), which would mean $66/sf for a consumer buying windows with VIG. Note that this price does not include any tariffs. For comparison purposes, standard double-glazed IGU in the U.S. is about $10/sf retail, with Passive House triple-glazed windows in the range of $30–$70/sf.

New VIG from Guardian Glass (made in the U.S.) and VIG Technologies (made in China) are poised to make serious inroads into the high-performance glazing market in the U.S. They are not cheap, but if their long-term thermal performance can be verified, they may very well be worth the cost.

Published October 22, 2018

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