For twenty years or so, companies like Pilkington () 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 10 years now. (See Images #1 and #2 in the Gallery, as well as 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 just did a big press event at an AIA conference for their two commercially available VIG products. And then there is Florida-based , a company that uses LandGlass VIG from China.
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 their units installed as retrofits at Eastern Michigan University (see Images #3 and #4 in the Gallery). 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.
So, what is the hold up?
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, This testing includes temperature extremes and accelerated aging/weathering testing. (For more information on this standard, including descriptions of specific tests, see )
A new standard
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,
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 is 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?
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 3 to get the consumer price (glazing installed in a window), which would mean $66/s.f. for 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/s.f. retail, with Passive House triple-glazed windows in the range of $30 – $70/s.f.
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.
In addition to acting as GBA’s technical director, Peter Yost is the Vice President for Technical Services at in Brattleboro, Vermont. He has been building, researching, teaching, writing, and consulting on high-performance homes for more than twenty years. An experienced trainer and consultant, he’s been recognized as NAHB Educator of the Year. Do you have a building science puzzle? . You can also to get a free report on insulation, as well as regular posts from Peter.