Haberer's GANA Presentation Focuses on Laminated Low-E Glass
April 9, 2009

Did you know using low-E glass in a laminated unit actually negates the low-emissivity (U-factor) performance qualities of the coating?

"This is because the low-E coating is buried inside the laminated lay-up," explained Jeff Haberer of Cardinal Glass Industries yesterday during his presentation, which was part of the Glass Association of North America's Glass Fabrication and Glazing Educational Conference in Cincinnati, Ohio. "A laminated low-E laminated glass does provide solar control," he added.

In his presentation on laminated low-E glass, Haberer talked about how low-E coatings and laminated glass can be used to make a great combination.

"Much like chocolate and peanut butter," said Haberer.

He explained that there is a need for these products because they can be used to meet certain code requirements and also improve visual aesthetics.

Haberer's presentation focused on emissivity and U-factor, solar control, coating types, as well as product concerns. He explained that low-E coatings are designed to reflect far infrared (heat) energy and that they need to have an air space, as in an insulating glass unit, to perform. When used in a laminated make-up, the coating reflects and absorbs ultraviolet and near infrared heat. Most of the visible light passes trough so the glass does offer high visible transmittance, as well as a low solar heat gain coefficient (SHGC).

Haberer also talked about the different types of coatings, sputtered (soft coat) and pyrolytic (hard coat). Both can be laminated and both have pros and cons. Product concerns for either include adhesion, aesthetics and durability issues.

When considering adhesion, Haberer said that with laminated glass, the way the interlayer bonds to the coating may be different than when working with non-coated glass. To make sure that the glass composition is right he stressed the importance of testing including the pummel test, boil test, ball drop and bag drop tests.

When considering aesthetics, Haberer said that layers are tuned to keep the coating neutral in appearance and the interlayer could shift in colors, so they may need to be adjusted to make sure you have the right color.

Durability issues, such as corrosion and delamination, also need to be addressed.

"Pyrolytic coatings are less susceptible to corrosion since they are fired onto the glass," said Haberer. "Sputter coatings are more susceptible since they are silver-based and silver, which is sensitive to moisture, can tarnish."

Likewise, there can also be concerns with the interlayer materials. Some, such as PVB, are hygroscopic, which means they tend to wick moisture away. He said while they do work, corrosion is still possible with PVB. Other materials, such as an Ionoplast interlayer, are not hygroscopic, so there is no moisture wicking and less risk of corrosion.

To ensure a product will perform, Haberer recommended both accelerated testing and field testing.

Assembly concerns can include knowing the right surface onto which the coating should go. Haberer suggested the number two or number three surface, though the number three side could offer better adhesion. However, he noted that on the number three side UV is blocked by the interlayer, offering higher reflectance and better SHGC.

Haberer added that it is important to make sure and select the glass make-up that will best optimize the performance, aesthetics, durability and customer needs of the given application. And also, "Test to make sure your combination will work so that the product will be successful."

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