Seeing Clearly: Transparent Components Create New Aesthetic Possibilities

By Jordan Scott

Increased transparency has been a growing trend for years, thanks to larger and larger sizes of glass and minimal framing that helps reduce sightlines. Now, companies are introducing transparent components and sealants to create further transparency in insulating glass units (IGUs).

While these products are pushing the aesthetic boundaries of architectural glass, they aren’t likely to be used on every building. Manufacturers and suppliers anticipate these products will be used for applications where transparency is of upmost importance.


Architectural Glass North America (AGNORA), based in Ontario, Canada, has created an IGU-to-IGU corner junction without anything visible in the corner. According to Louis Moreau, AGNORA’s head of technology and innovation, the product has been on the company’s research and development agenda for a few years. AGNORA is currently testing a prototype which uses proprietary glue in the corner to hold the IGUs together. Moreau says the company plans to offer an Insulating Glass Manufacturers Alliance (IGMA) certified unit with a warranty. He adds that, excluding the corner, the rest of the IGU is conventional. As for possible applications, Moreau says the first market will most likely be high-end residential projects.

“Curved glass could be used in the corner, but it reveals a double image that can be distorted,” he says. “This is like having nothing there. It’s open on both sides. From the interior it’s quite striking.”

Moreau describes the process of making a corner IGU as an artisan process. He says the company could not make 20 corner IGUs like that per day.

“Now it’s really time-consuming and expensive to do,” says Moreau, who adds that the company is working on industrializing the process.

Another challenge is that the structure of the corner IGUs cannot support the surrounding load, requiring a cantilever. While the demand for this glass is purely for aesthetics, the corner-to-corner IGUs still must meet energy efficiency requirements. Moreau says AGNORA uses coated glass with no edge deletion inside the IGU so there is coating against coating. The IGUs include stainless steel spacers and the glass is the same color as the
adjoining windows.


Jean-Paul Hautekeer, global strategic market director for high performance building at Dow Consumer Solutions, which is based in Midland, Mich., has also noticed architects’ increased desire for more transparency without compromising thermal efficiency.

“Architects want the edge seal and the perimeter of glass to be more natural,” he says.

Dow began offering structural silicones in more natural colors, such as different shades of gray, to meet that demand. Later, the company realized there was an opportunity for a transparent structural silicone and started the development phase.

The ability to create a transparent silicone lies with the chemistry. The key was finding a filler with the same refractive index of the silicone polymers to end up with an optically transparent silicone.

DowSil TSSA, a transparent silicone structural adhesive, allows architectural
glass to be installed without the need to drill holes, which prevents gas-leakage due to deteriorated gaskets. Hautekeer says TSSA is suitable for point-fixed glazing applications and all-glass architectural projects such as Apple stores. The technology can also be used on glass stairs and high-end balustrades.

One challenge TSSA presents is that the more transparent a project, the more critical installation becomes. Any defects in the application of the silicone will be magnified, says Hautekeer.

“Attention is needed when applying this product … Dow has a system where we sell the product with a project management system. We want to work with customers to advise on the best way to use these products,” he says.

He adds that Dow’s technology provides firmness and flexibility to account for building movement. The next step in transparency for Dow is to develop a transparent IGU with a transparent spacer. The company has developed this technology for use in consumer refrigerator applications but not yet for the architectural market.

“We’re working on potentially getting additional transparency on the edge of an IGU. We’re in the research and development phase now. It’s an exciting direction for us,” says Hautekeer.


A glass spacer may seem more conceptual than a reality, but sedak, of Gersthofen, Germany, has developed a glass spacer for architectural use. The task came about when sedak was approached by an architectural firm in Switzerland to replace glass spacers used in a project 25 years ago.

The sedak Isopure spacer can be used in the vertical (visible) glass edges and corners of IGUs to provide a transparent appearance. The company can manufacture a spacer up to 196 inches (5 meters). If the glass is larger, two spacers would have to be stacked on top of each other. However, the joint is not at eye level and not noticeable.

Maic Pannwitz, vice president, says they’ve seen interest from architects, however, there is still some hesitance since the glass spacer hasn’t been used widely.

“They have the feeling that they’re taking on the full risk of everything,” he says. “For now, in a project we’re working on, we’re giving them the full warranty.”

Pannwitz always recommends a visual mock-up so that architects and project stakeholders are aware of what to expect. He says the biggest challenge is to apply the spacer to the glass without the glue creating any bubbles.

“If you’re at eye level with the glass and you can see bubbles it hurts the eyes,” he says.

Pannwitz anticipates the glass spacer being used for storefront and lobby facades as well as residential buildings.

“People want an unobstructed view. Sometimes it’s not logistically possible to put a big lite of glass in,” he adds.

The glass spacer is more expensive than a conventional spacer, but Pannwitz says that part of sedak’s product development was to make it as energy efficient as possible. He says its U-values are comparable to a conventional spacer.

The company’s next step is to set up its fabrication so that the glass spacer can be sold as a regular product rather than a special product. Pannwitz says it’s important that if an IGU with a glass spacer gets damaged, sedak can replace it quickly. The company fabricates the entire glass unit. It does not sell the spacer separately, so an IGU with a glass spacer must be fabricated in Germany and then shipped to the jobsite, which can add to the cost, particularly when shipping to the U.S.

Transparent components for IGUs and other glazing systems are starting to be developed and installed in projects. While the cost may prevent these products from being used extensively, they certainly have a place in high-value projects designed by architects who value transparency and aesthetics.

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