Opportunities and Challenges for Acceptance and Adoption of Thin Glass Triples

Ellen Rogers

No matter how promising the performance, market acceptance of new glazing products and technologies often moves at a snail’s pace. Everyone wants to see it before they’ll believe it—and buy it. Electrochromic glazing knows this all too well. It’s been readily available since the early to mid-2000s and is now shifting closer to the mainstream, thanks partly to recent tax credits.

More recently, the architectural glass industry turned some attention to thin glass products measuring around 1 mm thick, sometimes a little more, sometimes a little less. These glass products are rooted in the consumer electronics industry, used in smartphones, tablets and smartwatches. Strength and scratch resistance are important for those applications—characteristics that are also important in architectural glass.

In 2012 the architectural glass industry got a look at thin glass possibilities when Corning brought its Gorilla Glass to the glasstec trade fair in Düsseldorf, Germany. The company focused on its potential in the architectural market, highlighting lightweight and durability. Two years later, Corning returned with a concept application that offered a glimpse into one possible use of thin glass. The display featured a retractable-foldable canopy constructed with Gorilla Glass that was laminated by SFL of Austria. This was only an example of what might be possible with thin glass. In reality, thin glass products are used architecturally in applications such as elevator cab systems, as a durable, lightweight material that provides a way for designers to customize appearances.

Thin glass triples—triple-glazed insulating glass units (IGU) that use thin glass as the center lite—represent another emerging opportunity. Also called skinny triples, these IGUs have been available since around 2020 and are just scratching the surface in terms of awareness, interest and use. However, not everyone is convinced something so thin will keep its promises. As with most new products, seeing is believing, and some still want to see more.

Thin Thinking

To understand where thin glass technology is going, first, understand where it’s from. Thomas Bertin-Mourot is the Advanced Windows innovation growth leader for Corning Inc. He says the company invented the fusion process (see sidebar on page 51) in 1964, which by the 1980s had “revolutionized the way liquid crystal display glass was manufactured, making thin, flat glass with exceptional thermal stability and unparalleled surface quality.

“Corning’s fusion platform remains central to several of [our] key business units, including display, mobile consumer electronics, automotive and now architecture—with the company expanding into this space as one of the first manufacturers to produce an ultra-thin glass substrate and manufacturing process to meet the needs of the architecture market,” he says.

Corning’s most recent thin glass development is its Architectural Technical Glass (ATG). Bertin-Mourot says this ultra-thin glass was developed in response to the U.S. Environmental Protection Agency’s new Energy Star Version 7, set to take effect in October 2023.

“Current mega trends in the architecture market are pushing windows to do more for us—including larger windows that let in more natural light. Historically, adding layers of traditional window glass often resulted in heavier, bulkier windows with reduced optical clarity,” says Bertin-Mourot. “However, an additional layer of Corning ATG configured as the center pane of a traditional double pane window cavity can help enable that performance while also improving acoustics, optics, storm protection and home security.”

Alpen High Performance Products, based in Louisville, Colo., has been at the forefront of lightweight, high-performance glazing, working with suspended coated films in IGUs for 40 years. CEO Brad Begin says their work is a 50-50 split between commercial and residential applications. The company was introduced to thin glass in 2018 through contacts at the Department of Energy (DOE).

“We began our testing with thin glass and introduced it in products about 3.5 years ago,” he says. “We first did a ton of testing and validation, and as we got comfortable with its durability, we began introducing it as an option to suspended coated film.”

Thin glass, he says, means different things to different people. “For us, it’s in the .5 mm to 1.3 mm range. When we use it, about 20% is in quad units. We use traditional low-E coated glass on the outside and thin glass as the center layer or layers,” he says.

Driving Forces

With increasingly stringent energy codes nationwide, the industry is seeing a growing push for high-performance products. Begin says thin triples can help existing products meet new and evolving energy codes.

“Most of what we do is in colder weather, but we ship all over North America to all climate zones,” he says. “Where we see the most growth, though, is in pockets of the U.S. [where there are] rapidly evolving energy codes (the West, upper Midwest, Northeast) and an interest and need for high-performance products.”

He adds that there is also tremendous interest due to its low-carbon features.

“[Float] glass is energy-intensive, and this is a low embodied carbon solution compared to big and heavy traditional windows,” he says.

Thin glass triples may offer a solution that can help improve energy performance, but not everyone is convinced it can stand up to the job. Cocerns about strength, durability and field performance are some of the primary concerns.

“When we first started working with thin glass, we thought it would be fragile and breakable,” says Begin, “but it’s substantially more flexible … the flexibility allows it not to break. It’s easy to handle and manufacture. And, because it’s not structural, that puts less stress on the edge and overall IGU and we think likely improves long term durability of the insulated glass unit.”

In constructing their IGU, he says, they index the center lite back slightly from the outer lites and have had “literally zero field breakage of the center lite(s) in the field from edge stress or thermal stress to date.”

Begin says they have also done various tests, including extreme thermal stress testing at Lawrence Berkeley National Laboratory and destructive load testing, to prove its strength and durability.

“We can validate and verify with testing and units in the field,” he says.

Production and Assembly

Another common question or concern about thin glass involves how it’s handled and processed.

“It goes through all the same processes [as a dual glazed unit] … cutting, washing, spacer application … and it’s easy to handle,” Begin says.

Until recently, thin triple IGUs were assembled manually, as automated equipment wasn’t available. “A year ago, you could not find an automated IGU line that could handle thin glass. There are now two excellent solutions, and we will be investing in automating our facility in Colorado,” says Begin.

One of those solutions comes from PDS IG Equipment in Prairie du Sac, Wis. Mike Rapp, president of sales, says their approach uses a single spacer rather than a traditional triple-glazed, two-spacer approach. The company’s equipment allows customers to produce dual- and triple-glazed units on the same line. Gas filling, assembling and sealing are all done the same as in traditional production.

“Historically speaking, things move slowly in our industry, and the PDS system allows IG fabricators to make the shift from duals to triples more gradually,” says Rapp.

He continues, “Our system essentially takes the middle lite and wraps the spacer around it. With the single spacer triple, a thin center lite can be used because the two cavities are connected. We have a groove in the spacer, which is part of our T17 flexible stainless steel spacer system.”

As far as whether the equipment could handle other types of spacers, Rapp says potentially it could, but right now, they are concentrated on the T17 spacer.

“It could potentially work with others out there. Currently, our application process is patented for how we wrap the spacer around the center lite,” he says.

One challenge of using a thin center lite,Rapp says, is controlling and accommodating the windload.

“In the past, fabricators would drill a hole in the center lite of glass; now the center lite is undercut compared to the outer two lites, so there is enough communication that the pressure goes from [lite] one to three,” says Rapp. “It’s an internal component that gives an improved thermal performance. The Insulating Glass Certification Council views it as a dual-pane with an internal component, creating two convection cavities.”

Corning also confirmed it has both product and process expertise to help enable the industry to incorporate thin glass into their product designs. “We are continuing to develop a family of thin, lightweight glass technologies and process innovations for windows, and we look forward to sharing more information as updates become available,” the company told USGlass magazine.

Fabrication and Installation

Thin triples are glazed into framing—windows and curtainwall—the same way as any other IGU.

“There is no difference,” says Begin. “Early on, we manufactured the largest IG unit we could at the time (50 square feet) for destructive testing in a traditional curtainwall configuration. We simulated increasing repeated negative and positive wind speed pressure in the test chamber to simulate buffeting winds one might find in extreme weather events. The windows broke at the equivalent of 227 miles per hour wind speed, and the thin glass was the last thing to break.”

Bertin-Mourot says his company’s thin glass works seamlessly with existing window materials and building practices, which can help the window industry reduce capital investments while meeting market pull and industry demand for lighter and more energy-efficient windows.

“With a profile of less than a millimeter thin with a long edge of 10 feet and above to let in more light, triple pane windows featuring Corning ATG deliver up to 25% better insulating performance for a minimal weight increase when compared to a standard double-glazed unit window,” he says, adding that lighter and less bulky windows, can also facilitate improved installation and transportation logistics for installers. For example, a 3- by
5-foot thin triple IGU could weigh around 28% less than a traditional triple-pane IGU.

“This weight savings cascades into a window solution that is light enough for a single person to install. In addition, high-performance thin triple IGU windows are designed to fit into an existing footprint which allows architects and builders to use standard building practices without compromising existing window areas or a major window refitting.”

Challenges to Market

Joe Erb, national account manager with Quanex Building Products, says while skinny triples offer a lot of potential, much of the industry is wrestling with concerns and questions.

“From a certification point of view, how do we handle it? From a definition point, how do you define it?” questions Erb.

The Fenestration Glazing Industry Alliance is working to address these matters. Rapp is chairing the group’s thin glass and multi-cavity units task group, which was formed at this past winter meeting. He says the group is working on creating definitions and cohesion among the various information and terms.

Aside from these explanations, Erb says there are other fundamentals to address.

“The industry is working through the definitions and the terms we want to use to be technically sound to bring these products to market, and it seems to be gaining traction and interest,” he says. “However, one question to address is what you do in cases where tempered glass is needed [for safety glass applications] since the thin glass cannot be tempered.”

According to information provided by Corning, the company “is working on multiple solutions and assessing with customers and industry partners how to best integrate thin glass into window applications while meeting the ANSI Z97.1 [American National Standard for safety glazing materials used in buildings].”

Begin adds that in his company’s products, both exterior lites are tempered, and while the inside lites are not tempered, the company has a tested solution to meet codes. He agrees that in a safety glazing application, the use of thin glass as the center layer in a tempered unit is an issue the industry is sensitive to and interested in better understanding. “We have studied it intensively and understand it extremely well. We have multiple tested and practical solutions to the issue of how to use thin glass in a safety glazing application, but because it includes confidential and proprietary information, we are prepared to share our learnings and solutions with the industry on a case-by-case basis in individual discussions with whoever is interested in learning more.”

Commercial vs. Residential

While Alpen offers its thin glass triples as a solution for commercial and residential applications, others see residential as the true starting point.

“We see [commercial applications] as the second phase of market adoption because it’s a more risk-averse market,” says Erb.

“I think there will be earlier adoption of something a bit thinner [for commercial], but not to the extent of the ultra thin residential glass we are seeing,” he says.

Mark Molinaro, director of new markets and business development with Quanex, says residential and commercial products need different approaches.

“I don’t think anyone has taken that step as it applies to commercial windows,” he says. “Once the safety glass issues are overcome, it will expand quickly.”

And when the market is fully ready, Erb says Quanex will also be prepared with its solution.

“Our Super Spacer® construction is a technology we know works. We feel we have the solution when the market is ready, but we’re not going to over-promote it when there are areas the industry still needs to address,” he says.

Speaking of differences in spacers, Molinaro says Quanex developed a process that creates a slit [in the spacer] to cushion and hold the glass between the two outer lites.

“This allows the two cavities to communicate since it’s not a sealed unit. It fits within the process easily,” he says.

The industry is facing a big opportunity with thin glass triples. However, given that traditional triple-glazed units currently comprise a Quanex developed a process for skinny triples that creates a slit in the spacer to cushion and hold the thin glass between two outer lites.

“This allows the two cavities to communicate since it’s not a sealed unit. It fits within the process easily,” he says.

The industry is facing a bof opportunity with thin glass triples. However, given that traditional triple-glazed units currently comprise a mere fraction of the market, it could be some time before thin triples see significant growth. Aside from some of the questions and concerns, there’s also the matter of cost. According to the DOE, thin triples cost 10-40% more than typical windows. As production volume increases, the price will come down.

Rapp sees durability in the finished product as likely the biggest obstacle to address.

“I think that’s an area where companies may be a little nervous because the complexity of these units may offer more [potential for] failure,” he says. “I feel that’s where our process is more like a dual-pane, and people can be more comfortable from a durability perspective.”

For Begin, though, there are far more reasons to advance the use of thin glass triples than to hold back.

“The marketplace needs to get past [reasons] why it can’t work,” he says. “There are dozens of field validation reports. I’m surprised it hasn’t been grabbed up as an obvious technology solution that’s practical, effective and affordable-especially for the many excellent but narrower frame designs preferred in the United States marketplace.”

What is the Glass Fusion Process?

Corning’s fusion process is an essential part of the company’s thin glass products. But what is it, and how does it work?

According to the company’s website, raw materials (pure sand and other inorganic materials) flow into a large melting tank. “The molten glass is homogenized and conditioned before it is released into a large collection trough with a V-shaped bottom, known as an isopipe. The isopipe is carefully heated to manage the viscosity of the mixture and ensure uniform flow.

“Molten glass flows evenly over the top edges of the isopipe, forming two thin, sheet-like streams along the outer surfaces. The two sheets meet at the V-shaped bottom point of the isopipe and fuse into a single sheet.”

The website explains that while still attached to the bottom of the isopipe, “the sheet feeds into drawing equipment as it lengthens and begins to cool in midair … The sheet is carefully cooled and stabilized until it reaches the bottom of the draw, where it is cut and moved to a nearby area to complete processing and packaging.

Ellen Rogers is the editorial director of USGlass magazine.
Email her at erogers@glass.com and connect with her on LinkedIn.

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