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In 2008, a Dutchman named L. Korn found himself in Toronto buying windows for a house he was building back in the Netherlands. Unavailable at the time in Europe, the quad-pane insulated glass he wanted could be ordered from a Canadian manufacturer, and Korn was ready to do business.
Korn placed an order for 193 insulated glass units — just the glass, no frames — with Eco Insulating Glass Inc. of Mississauga, Ontario in April 2009. The $40,400 order went to a warehouse in New York and from there was shipped by sea to his house in the Netherlands. Carpenters inserted the glass into frames that had been made in Guatemala and installed them.
The krypton-filled insulated glass units (IGUs) consisted of two sheets of glass and two sheets of Heat Mirror film. The high-performance windows were part of Korn’s plan to use only the best green building materials he could find in the construction of his 3,000-square-foot, €1.2 million home. He also bought one spare unit and stored it in a garage, just in case something happened to one of the windows in the house.
And by 2016, something did start to happen to the windows in his house. They began imploding.
“The first IGs imploded in 2016,” Korn said in an email. “It made a big bang. I had no idea what happened. I reported the problem to Eco Insulating Glass on 29 November 2016.”
Now, two years later, a total of nine windows have imploded. The manufacturer blames the problem on Korn’s decision to glue wood grilles on the outside faces of the glass and has voided its warranty. An engineer hired by Korn says the practice is common in Europe and that a manufacturing defect, not the grilles, is the most likely reason that the glass panels are failing.
In the meantime, Korn is left with a number of shattered windows and a €135,000 estimate to replace them.
The problem is not unknown
Insulated glass units consist of two or more panes of glass, with the sealed space between them typically filled with gas, often argon or krypton. After the units are manufactured, the outer panes of glass are susceptible to some distortion as temperature and air pressure change, says Dutch engineer Walter Frank Westgeest. The phenomenon is well known in the glass industry, but it rarely results in a problem.
“Yes, I’ve seen many glass panes that are curved by air pressure differences or other causes, but it hardly ever results in breaking,” Westgeest said in a telephone call. “If you look at buildings, you can see all kinds of curvature in the glass panes, especially with a certain ratio of length and width.”
An exasperated Korn hired Westgeest to find out what happened after an extended exchange of emails with the manufacturer got him nowhere. Westgeest, who works for the Dutch firm Bouwkans, is a building scientist who spent 10 years working solely for a glass consultancy.
In a report on Korn’s windows last year, Westgeest said that all of the IGs he inspected, except for one, appeared to be concave, with interior panes always distorted more than the exterior pane of glass. The wood window grilles that had been glued onto the glass were often detached, meaning they had pulled away from the glass and could no longer impede movement.
Westgeest said that he measured distortion with a straight ruler and a sliding gauge. The distortion ranged from 2mm to 8 mm (0.06 inch to 0.31 inch) on the inside pane, and from 1 mm to 4 mm (0.03 inch to 0.157 inch) on the outside pane. The uninstalled spare unit also showed an inward distortion: 3.8 mm (0.149 inch) on the inside pane.
Why do glass surfaces deflect?
Westgeest cites three reasons why insulated glass units become concave or convex in shape:
- The gas content inside the IG is constant, but the ambient air pressure where the window is installed varies. The IGU is convex at low ambient air pressure and concave at high ambient air pressure. He describes this as a “dynamic process whereby the IGU will eventually return to its original flat shape …” It is not, he adds, enough to break glass panes, but the effect is magnified when the unit was manufactured under air pressure conditions significantly different than where the windows are put into service.
- Sealants and spacers are designed to contain the gas inside the IGU, but the gas can still leak out. Argon and krypton have a tendency to move from an area of high concentration to an area of low concentration, and materials used for sealant barriers let some molecules go through more easily than others. Krypton and argon can get out, but larger oxygen and nitrogen molecules in the atmosphere can’t get in to replace it. Westgeest calls this a “molecular sieve.” In time, the sealed space inside the window is at a much lower pressure than ambient air pressure.
- A dessicant is placed inside the sealed space to absorb moisture, but when a dessicant with the wrong specifications is used, gases like argon, krypon and nitroten are absorbed instead. “Because these gases are the main content of these IGUs, the absorption or ‘disappearance’ leads to a lower pressure in the unit, which will lead to concave shaping of the IGU,” his report says.
Westgeest said the insulated glass industry has, in time, learned to cope with these problems and that reports of glass failure now are unusual. For example, IGUs can be subjected to big differences in air pressure when they are shipped from a low-altitude manufacturing plant to a house high in the Swiss Alps. Manufacturers counter the problem by inserting very small tubes that vent the interior of the window and let excess pressure escape. When the windows arrive at their destination, the tubes are sealed.
Westgeest believes that either a faulty dessicant or a faulty sealant is to blame for Korn’s window problems. “I can’t imagine anything else,” he said. “That’s the only thing I can really think of. It can be worsened by transport, but I don’t think that’s the primary cause.”
In the U.S. early IGU makers learned to tweak the internal pressure of the windows so they wouldn’t rupture on the trip from a manufacturing site in the Denver area (elevation of 5,000 feet) to the Houston area, one expert who didn’t want to be quoted by name told GBA. Early on, windows failed. Then manufacturers learned how to adjust. These days, failures on the scale of Korn’s experience are rare indeed.
The manufacturer blames the applied grilles
Glenn MacEachern, vice president for sales at Eco Glass, believes the problem with Korn’s windows stems from the decision to glue wood grilles to the outside of the glass, not a manufacturing defect.
That was the basis of a letter from Eco attorney Stephen Walters to Korn last year in which the company disavowed any responsibility for the breakage. Walters said the 20-year warranty on the window units excludes “glass breakage from any cause” and exempts units that have been retrofitted with “any type of solar film or tinted film or any other added covering to the original glass surface.”
“We have inspected the unit you shipped to Eco for review and note that your complaint is in respect of the breakage of the glass and that, in addition, the glass had an added covering to the original glass surface,” Walters wrote.
“As such, the products supplied are exempted from any warranty coverage. The glass breakage is excluded from coverage, and the glass was covered with a non-factory covering and excluded from coverage.”
Bottom line: “Eco has no obligation pursuant to the warranty or otherwise to replace the glass.”
In a telephone call, MacEachern said the grilles could interfere with the “pumping action” that any IGU undergoes with changes in ambient air pressure. “It’s a violation of the warranty,” he said. “A unit has to be able to change with changing environmental conditions.”
He said he suspects Eco’s warranty is no different on that point than a “vast majority” of IGU manufacturers. Moreover, Eco has not had any other complaints of this kind in the more than 30 years it’s been making IGUs with the Heat Mirror film developed by Southwall Technologies.
“If this problem were going to be across the board, we would have had a similar situation exist in production other than Mr. Korn’s,” he said. “This one example is the only one that we’re aware of … If there’s a problem with our production methodology then why is it just this one specific job? That’s it. I’ve not seen it anywhere else.”
The privately held company manufacturers IGUs, but not finished windows, for the North American market. MacEachern declined to be specific about production volume or sales.
A long string of emails goes nowhere
Korn has posted his tale of woe online, including a series of email exchanges with MacEachern, another Eco Glass executive named Jim Larkin, and officials at Eastern Chemical, which owns the Heat Mirror technology. The emails trace Korn’s repeated requests for an explanation and help, from the early days following the initial implosion in 2016 through his frustrated accusation last month that Eco Glass was refusing to take responsibility for its production errors and didn’t seem to care about damaging its reputation.
Eco at first seemed eager to help. In January 2017, MacEachern wrote that he was trying to find an engineer in Europe who could help assess the problem. He offered possible causes for the breakage — the frames around the units were too tight, or the sealant on the window edges was not sufficiently protected from UV light.
“Please rest assured that we are working diligently to address your situation,” he said in an email. In a followup email in April 2017, MacEachern told Korn that he was waiting to hear from Eco’s gas supplier as well as suppliers of polyurethane and silicone, who might also have some ideas.
“I’ve always been a proponent in assessing the root cause for failures so that we simply do not repeat the problem again for you,” MacEachern said. “I want to get to the bottom of things and correct the situation.”
But as time went on, the correspondence became less cordial.
By last month, Eastman was asking to be dropped from any further inquiries, and Eco made it clear it was at the end of its efforts to help.
“The bottom line here is that Eco Insulating Glass Inc. simply cannot be responsible for the mishandling or misuse of our product after delivery,” Larkin wrote.
Next steps uncertain
Korn, 56, said he originally found Eco through a Google search. No one in Europe was using Heat Mirror film at the time, so he piggybacked a visit to the Eco factory with a family trip. The visit went well. “It was all OK,” he said, “they’re not a big company.”
Separately, Korn had selected a Guatemalan firm at a building fair to manufacture the frames. He also visited that company before placing his order. The window frames were shipped separately to Holland where they were married up with the glass from Canada and installed in the house.
The windows were installed without incident, and it wasn’t until 2014 that someone pointed out to Korn that one of the windows seemed to have a concave shape. The following year, the first of the windows imploded, he said in a telephone call, but the window was in a room that didn’t get much use and he put the problem out of mind.
But the following year, two others went and Korn’s concerns grew. At Eco’s request, Korn removed a damaged window and sent it to the company for testing. On the advice of his engineer, he declined to send Eco the only uninstalled unit he had.
But, Korn says, he never was told what the tests revealed. Eco’s did not follow through on its initial offer to find an engineering firm in Europe to look into the problem, and the company did not comment on the results of Westgeest’s €1,200 report, he said.
In short, Korn doesn’t seem to have much leverage with Eco, and not much of a way forward without hiring a lawyer, a move he recognizes as an expensive next step. “If you start talking to a lawyer, the first thing he says is, ‘Well, send me 10,000 Euros and I’ll have a look into it.’ That’s the first thing they say,” Korn said. “… I’m looking into it but first I want to try if I could convince Eco Glass to handle this in a normal way.
“They have tried to get around it, and of course that has made me very upset and angry,” he continued. He hopes the website he has created will prompt others who have experienced the same problem to step forward, but so far none has.
“I have no idea,” he said when asked what he will do next. “I’m just waiting and hoping.”
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34 Comments
Some numbers in the article don't seem to make a lot of sense.
"Korn placed an order for 193 insulated glass units"
That's an awful lot of glass for a 3000 ft^2 house. I think that would almost certainly make the entire walls glass.
He paid $40,400 (presumably C$) for all (193!?) glass units, but the replacement of 9 is going to be over $200,000? I know there's other costs, but it still sounds nuts. Is that 193 supposed to just be 19? Even if it's half the windows, that would put a prorated price of $400,000 on the windows that he spent only $40,000 on the IGU portion originally. I'm guessing the frames may have doubled that, and with shipping and install it might come out to $100,000 for the entire lot. Still seems askew.
Trevor,
The house is 3000 ft x 2 floors and a cellar with ½ of it with glass doors hence the misunderstanding. In total I bought 193 IGU's from ECO Insulating Glass Inc. with HEAT MIRROR for my windows and doors.
The price is to dismantel all glass windows and doors and replace with new IGU's and the paint job.
I have attached a link of the report made by engineer Walter Frank Westgeest about the problems hope this will clarify your questions.
https://www.scribd.com/document/392503532/ECO-Insulating-Glass-Inc-Report-Insulating-Glass-Imploding-Problems-With-HEAT-MIRROR-film
I'm curious about what the expected life of good filled windows is. Is breakage and/or low R value at 25 years acceptable? Avoidable?
Trevor, That's about $207 each for each IGU, which sounds within the bounds of reason. I would imagine the costs quoted in the article are for replacement glass and the labor to install it. I would guess that most home owners, knowing that the glass was doomed, would rather replace all of them at once rather than replace them piece meal as they failed.
I'm not sure I agree that $207 is within the bounds of reason for high performance, quad-pane IGUs. But regardless, the sheer number of IGUs for a modestly sized house is the most eyebrow raising stat. I looked at the purchasers page, and at first I thought I saw an explanation: lots of tiny windows connected by mullions. However, on closer inspection those many windows are just one window with grilles on the faces of the glass. (Side note, why would anyone do that? Obstruct a clear view with something that has no other purpose that to obstruct your view.)
Trevor,
The grilles are a matter of design in many cities in Europe. In some locations we are obliged to place grilles on new windows to keep the look of old houses. ECO Insulating Glass Inc. does not mention in their Architect Information Binder (see attached) that glued on grilles would void their warranty. I have showed ECO Insulating Glass Inc. the drawings of my house where the grilles are clearly visible before we bought the IGU's and there was no mention that I would void the warranty by glueing the grilles.
https://www.scribd.com/document/383119017/Architect-Information-Binder-www-Ecoglass-ca-Eco-Insulating-Glass-Inc
Another off topic observation, didn't this guy completely defeat the purpose of buying these quad pane IGUs (expressly stated as "part of Korn’s plan to use only the best green building materials he could find", which I would assume has something to do with energy efficiency) by having them installed in wood frames? My understanding is that the frame contributes as much or even more to the overall efficiency of the window as the IGU. High performance PVC and fiberglass window makers go to great lengths to limit the thermal bridging within the window frame. A wood frame is a direct thermal bridge connecting the inner and outer glass.
Trevor,
You are absolutely correct about energy efficiency. My goal with building this passive house was to build it as green as possible, not only energy efficient but also environmentally friendly by using green building materials hence the FSC certified wooden doors and windows.
Something shady going on at the purchaser's website. He has this heading above a bunch of links to negative reviews:
"See down below links with reviews that i found on ECO Insulating Glass inc. :"
If you actually click on those links, you start to notice pretty quickly that they are all* reviews left by Korn himself. The wording "reviews that I found" is at best misleading, and sure seems like an intentional attempt to make it appear like lots of other people are complaining. I think it's pretty disingenuous to post a review at multiple different sites, and then point to them and say "here are reviews I found".
*all the links that actually lead to reviews; several links either go nowhere, go to somewhere unrelated, or to a listing of ECO without a review actually being there
Trevor,
Have a look at the report from engineer Walter Frank Westgeest about the IGUs imploding problems you can find links that show this problem on page 15.
IMO, the bottom line... Mr. Korn should've read the warranty's fine print.
Armando,
On 24 august 2017 I received a letter from a laywer Stephen Walters hired by ECO Insulating Glass Inc. to state that ECO Insulating Glass voided their warranty stating. "1. Glass breakage from any cause..... ; and 2 Units retrofitted with any type of solar film or tinted film or any other added coverings to the original glass surface."
This is completely fabricated and incorrect. I have attached the original Architect Information Binder that I received with the shipment there is no stament in any form described by lawyer Stephen Walters hired by ECO Insulating Glass Inc. in the binder.
Per this article and without prejudice, "Walters said the 20-year warranty on the window units excludes “glass breakage from any cause” and exempts units that have been retrofitted with “any type of solar film or tinted film or any other added covering to the original glass surface."" I guess it may take Lawyers and/or a Judge to decide who is right.
Having worked in the residential design and build industry for over 35 years, I've learned that all materials, systems and appliances must be installed per manufacturer's guidelines and specifications. All my specifications and working drawings have notes on every single sheet that outlines that fact. Contrary to such instructions, making any changes, make the Builder and/or Homeowner liable for all corrections.
Many years ago, I read a study based on court case result's, that said the over 85% of all construction defects were due to installations, 8% for design and 4% for materials or systems. Since then, I've used that information in all my presentations to teach the industry about Green Building and Building Science.
Armando,
You are correct that a Judge should have a look at a situation like this. The report from engineer Walter Frank Westgeest is very clear about this particular problem. It is the sealant used by http://www.ecoglass.ca/products .
Problem is that ECO Insulating Glass Inc. and Eastman Inc. (HEAT MIRROR) are not responding to my questions of what sealant is prescribed by Eastman with the use of HEAT MIRROR film and what sealant ECO Insulating Glass Inc. used with the production of the IGU's filled with Krypton.
The fact that they are not willing to answer these question shows that they are hiding something crucial !!
See attached the emails with questions i have send to ECO Insulating Glass Inc, ( [email protected] [email protected] ) and Eastman HEAT MIRROR film ( [email protected] [email protected] )
The only warranty in that document is:
"Warrant that sealed insulating glass units shall remain free from material obstruction
of vision as a result of dust or film formation...". Nothing about cracking caused by low pressure. Maybe if you can show an internal moisture film occurring.
I think it's reasonable to expect that a warranty would cover the self destruction of whatever the product is, if it can be determined that it was a result of a flawed design or manufacturing defect. Lots of complex products can fail in countless different ways, and those are not generally enumerated in the warranty statement. I don't think the fact that it doesn't specifically list cracking of the glass automatically gets them off the hook, and it is substantially different from including wording that specifically excludes it.
I only agree if the warranty had some general phrase such as "free of manufacturing defects". But I'm not a lawyer - perhaps there is an implied warranty of merchantability that extends beyond what is written.
Another view is that so far, it's just $2000 of IGUs - not worth much of a fight.
Jon,
Thanks for taking the time to read the Architect Information Binder of ECO Insulating Glass Inc.
You are correct that there is nothing about cracking caused by low pressure this is something ridiculous that the laywer from ECO Insulating Glass Inc.
Stephen Walters 6509 Mississauga Road, Unit B Mississauga dreamt up.
See the letter from Stephen Walters attached.
Yep, you're the only one we've ever had a problem with.
Now there's a statement that I've heard many times before.
Translation: We've had problems, but we're not owning up to them. How will you ever prove otherwise.
Mike,
I got an interesting email from the CEO Glenn MacEachern of ECO Insulating Glass Inc. on 12 January 2017 stating "In the meantime I have had a similar situation here locally over the holidays" .
I never received an update from the glass engineering company or http://www.ecoglass.ca of what has coursed the implosion of the IGU from their customer. See attached the email from the CEO of ECO Insulating Glass Inc. I am sure that Glenn MacEachern is regretting this email immensely.
It is dreadful how companies shamelessly try to get around their responsibilities and leave their customers with faulty products and costly damages.
My major complaint is with the CRM of these companies.
With little more effort, they could "cut the problem off at the pass", simply by conversing fully with their clients, instead of going directly in lock down mode and denial.
A while ago, I had a fault with heavy trailer brake linings that had separated from their respective brake shoe. You guessed it, I was the only one suffering this problem.
Today, aluminium brake rivets are banned from use.
I have numerous anecdotes like this, but I won't bore you with them.
I say again to all suppliers and manufacturers, talk to the complainant before going into denial.
Mike,
So true what you are saying.
ECO Insulating Glass Inc. CEO Glenn MacEachern and Eastman (HEAT MIRROR) Thomas R. Marsh believe with not responding or answering the questions raised that the problem with their faulty produced IGU's disappear.
They should take this problem seriously so they do not make the mistake again.
If ECO Insulating Glass Inc. and Eastman have any doubt that the report drawn up by engineer Walter Frank Westgeest is incorrect ECO Insulating Glass Inc and Eastman should appointed a 2e glass expert to investicate and come with a counter report.
On 2 May 2017 ECO Insulating Glass Inc. requested the following:
"Upon receipt of these failed / failing units back in North America , ECO would then enlist an outside independent laboratory to provide a written report as to the cause of the implosion(s)"
On 23 May 2017 I sent one imploded unit to ECO Insulating glass Inc., 1416 Bonhill Road Mississauga, Ont. L5T 1L3, Canada for them to have it tested.
ECO Insulating Glass Inc. never came with an report or any coment about the laboratory test neither did they report to me what they have done with the unit.
Again this is telling us that ECO Insulating glass Inc. and Eastman (HEAT MIRROR) are hiding the truth about the sealant they have used to produce the insulating glass with HEAT MIRROR and Krypton gas!!!
Since the windows were made in Canada and then traveled half the globe to get to Europe. The windows went through elevation changes ranging from sea level to probably over 7,000 feet. This put tremendous pressure on the glazing.
Did the manufacturer install some type of breather system to allow the gases within the windows to expand and contract as they traveled half the globe before reaching their destination?
Peter,
Thanks for mentioning your concern. Engineer Walter Frank Westgeest did a thoroughly research on your point the shipment passed 1800 feet on its highest point have a look at page 5 in the Investigation of damaged Insulating Glass Units report drawn on feb. 2017
https://www.scribd.com/document/393351673/ECO-Insulating-Glass-Inc-Report-Insulating-Glass-Imploding-Problems-With-HEAT-MIRROR-film
ECO Insulating Glass Inc. knew that the IGUs had to be shipped to The Netherlands.
I wish ECO Insulating Glass Inc. had put in a breather system, the IGUs would have lost the Krypton gas but in the end NO CONCAVE AND IMPLODING WINDOWS !!!
Peter,
What? 7,000 feet?
The windows were manufactured in Mississauga, which is conveniently located near the shore of Lake Ontario. Mississauga's elevation is 512 feet. The windows were probably put in a container, and then on a freighter that traveled down the St. Lawrence Seaway to the Atlantic Ocean, and thence to Holland. The highest elevation in Holland is 1,000 feet.
It's very, very difficult for an ocean-going cargo ship to reach an elevation of 7,000 feet.
Martin,
I was referring to mountain passes on land during transport once the windows reach land. For example, windows made in Phx, AZ at 900 feet elevation being transported to Flagstaff, AZ in just 3 hours of road travel will see elevations from 900 feet to over 7,000 feet elevation in just 3 hours.
There still needs to be a breather system to allow the gases within the windows to expand and contract as they traveled to their destination. Without it, even a double pane window can implode.
I believe the problem has nothing to do with the heat mirror. It's an issue of the glass experiencing stresses. I've seen true triple pane glazing implode due to the lack of proper breather tubes. These were European windows with 3 actual glass panes that imploded after a few months of being installed.
Peter,
Can you identify a mountain pass between Mississauga, Ontario, and the Netherlands?
The highest point in the Netherlands is about 320m (1000'). I don't think this guy lives on the top of that mountain, however (and it's nowhere near the sea coast). So the maximum likely change in elevation was between the factory and sea level, about 150m.
Even if the windows did undergo a large elevation change, if the windows were going to implode due to that, wouldn't it happen around the time the elevation difference was experienced, rather than years later, when it's at approximately the same elevation as they started?
Martin,
I was just making a general comment about window transportation from factory to job site and how elevation changes put stresses on the glazing. Without the proper breather tube assembly, these stresses can result in windows that shatter months or even years later.
I did not do a geographic trace of where the windows were made, the route taken, the semi truck that picked up the windows and the route it traveled before delivering to the job site.
I would also add that semi trucks pick up not just that single freight of windows but numerous other freight, fully loading the semi. That semi will travel to different places before it actually stops and delivers the windows at that job site. I've seen trucks pick up windows in a Texas sea port and then travel in elevations of over 7,000 feet and back down to 900 feet, making over 8 stops before delivering windows. So those windows saw elevations from just above sea level to mountain passes, back down to below 1,000 feet.
I am sorry for the confusion. I did not research the geography of the Netherlands and Ontario and I was not aware of the ledger route the windows took from truck to shipping container back to truck.
There are a few possible lessons from this story. One concerns the possibility that IGUs can distort, becoming convex or concave; I looked into that phenomenon for a series of articles on reflections from windows that melt vinyl siding. (For more on that issue, see "Window Reflections Can Melt Vinyl Siding.")
The second possible lesson -- and this is speculative -- is that the well-known fact that European window manufacturers have chosen to avoid the use of suspended plastic films (Heat Mirror technology) in favor of true (all-glass) triple glazing may be based on appropriate caution.
The third possible lesson is that a homeowner gets better warranty service when purchasing manufactured windows than when purchasing IGUs from one supplier and window frames from another supplier, and then hires a local contractor to put the parts together and glue wooden muntins on the glass. In the latter case, the homeowner because a fabricator, and assumes much of the liability traditionally assumed by window manufacturers.
Fourth: read the warranty carefully and make sure it covers all the failure modes of interest.
The third one is especially important. Even if ECO did honour the warranty, their only obligation is to replace the units, or issue a refund. So that would still leave him with a loss of about $160,000. Whereas if he bought the windows as full units, and any part of them failed, the supplier would be looking at replacing the whole window.
Martin et al,
I am a (very satisfied) Colorado customer of Alpen HPP window Co. I live in Colorado and the NetZero project in which we used their suite of windows in is located 8 miles from their plant. Still a minority of the windows came over with breather tubes and their (proprietary ?) gas filled flexible bladder for site sealing. Why, some uits and not others, I don't know. Of interest here, Alpen as spec'd., supplied from the factory their composite, adhered muntins on both exterior and interior glazing - one of their standard options.
As you may know the Alpen IGU and that of the ECO company appear to use very similar components- both using up to 2 Heat Mirror films for interior insulating chambers. Alpen has developed their own system for manufacturing the IGU's in house using their materials and methods. You can see in their marketing that they are very sensitive to the longevity and reliability of their units. They are recently installed in the Empire State Building rehab. project as a testament to how developed the technology has become. I see no advantage to using 3 heavy sheets of glazing as the Euros seem to think is so wise. We know the stories of installing these monsters
Personally I would think that the muntins would offer added reinforcement to the glazing enhancing the resistance to any deformation. I suggest that in our 130-160 wind design area that a bigger component to all of this could be due to the gust loading that would affect large area IGU's especially the lift and slide doors he is probably using. I might suggest to Mr. Korn that he investigate the Alpen HPP system with their use of applied muntins.
What is the total airspace thickness? Units with multiple glazing layers act like dual glazed units with larger airspace thickness. You would not make a dual glazed IGU with a 2" airspace, that's four times the air in the unit to expand and contract according to the ideal gas law PV=nRT. This would result in much greater pane deflection than a typical IGU.
Alan Dalglesh formally of the National Research Council (now retired) did extensive research during the development of the Canadian Glass Standard CAN/CGSB 12.20M, and developed software tools for predicting glass deflection and strength of IGU's in response to wind loads, barometric pressure and temperature changes, and elevation. He might be able to assist with some analysis, but I suspect the root cause is loss of krypton which is not being replaced with nitrogen due to sealant and dessicant selection.
Have you considered installing capillary tubes?
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