At the Fenestration and Glazing Industry Alliance (FGIA) Virtual Summer Summit, industry leaders tackled critical technical challenges. Experts led high-impact, interactive sessions on sealant selection, the new version of the North American Fenestration Standard (NAFS) and complex window glass design, equipping professionals with actionable strategies to elevate product performance.
Learning About Sealant Compatibility
In the panel “Sealants: Compatibility and Performance for Proper Selection,” three industry experts provided their distinct points of view based upon their unique experience and expertise, including Steve Altum (Dow Performance Silicones), Lori Dahlman (Bostik) and Brandon Rhoades (H.B. Fuller).
Rhoades discussed the testing and performance of sealants, starting with the difference between a single and a dual seal within an insulating glass unit (IGU). “A single seal has one seal along the edge, sealing the air space of that insulating cavity,” he said. “Dual has a primary and a secondary sealant, with the secondary being the outermost one. The primary is to be a moisture barrier and keep gas in. The secondary is meant to provide support and strength.” He warned single seals are only suitable for non-structural glazing applications.
Dahlman focused on setting windows in their frames and testing back bedding sealants. “A back bedding sealant creates a bond between the glass and the frame,” she explained. “It protects the unit from air and water.” AAMA 800 is the only specification used for a back bedding sealant, she said, adding that, if one is using a sealant in the field that doesn’t pass the prescribed tests within, “we want to know about it so we can expand on those minimum specifications.”
Altum shared his expertise on the use and performance of structural sealants, stressing it is important to know what one is trying to achieve with the application. “What is the required design performance? What market or geographical location is a job or product being sold into?” he asked. “It’s important to talk with your sealant suppliers and walk through different scenarios. Just because a sealant is approved doesn’t mean it will give the best adhesion possible for a specific application.”
The Standard of Window Glass Design
Dr. Stephen Morse (Michigan Technological University) presented “Window Glass Design Fundamentals: From Basic Principles to Modern Practice.” In this session, he introduced the fundamental mechanical behavior of architectural glass and the factors that influence its strength and performance. Morse explained how glass type, thickness, size, aspect ratio and support conditions affect load resistance and probability of breakage, then he described the role of an ASTM standard in the design and evaluation of window glass systems.
“Glass is brittle,” Morse said. “It fractures at relatively low tensile stresses due to the existence of surface flaws, exacerbated by surface damage. It makes the glass weaker.” Morse said that, over time and due to weathering, a surface flaw can reduce glass strength to approximately 60 percent of that of new glass.
For guidance, Morse recommended ASTM E1300, Standard Practice for Determining Load Resistance of Glass in Buildings. “It is used for uniform lateral load, geared toward windows and buildings and windload,” he said. “It applies to monolithic and laminated glass constructions of rectangular shape with continuous lateral support along one, two, three or four edges.” It also applies to insulating glass units with four-sided edge support, he said. Future updates to ASTEM E1300 will include expanded non-factored load charts and an expanded glass failure prediction model.
“As part of a research project, we are getting vacuum insulated glazing units from three manufacturers in three different sizes, thanks to FGIA and National Glass Association funding,” he added. “Testing is ongoing.”
Understanding Changes to NAFS
A panel discussion titled “NAFS-26 | Understanding the Changes and Impact on Testing Requirements” gave participants an idea of what to expect from edits made to the new version of the standard, which came out June 1. Panelists included Lisa Bergeron (JELD-WEN), Robert Jutras (UL Canada) and Dan Raap (AmesburyTruth), all of whom worked on the update.
The primary change in NAFS-26 clarifies requirements for the secondary designator used in fenestration product ratings. The change was proposed by the Federal Emergency Management Agency (FEMA) and accepted following discussions with the developing group. Previously optional, the secondary designator is now mandatory and must be included on product test reports and labels. The secondary designator now requires performance values for positive design pressure, negative design pressure and water penetration resistance test pressure.
“The FEMA proposals were also echoed from the Florida Building Commission, which provided us that additional push to make changes in NAFS,” said Bergeron. She noted that there will need to be additional labeling that will be worked out with the certification bodies and that marketing documents may need to be updated from just design pressure ratings to include performance grade ratings.
“The change was driven largely by increasing concerns related to water intrusion performance, particularly in coastal and hurricane-prone regions such as Florida,” said Raap.
Another change included the addition of a new FGIA document, AAMA 517, Specification for Air/Water Penetration Resistance, and Structural Load Performance of Multi-Track Doors and Windows. “AAMA 517 directs all requirements to NAFS and does not create any differences if following that pathway,” said Jutras.
