Glass Breakage in Insulated Glazing Units in Spandrel Assemblies

This presentation initially took place at the 2020 Convention.

Curtainwall and window wall systems today commonly use insulating glass units (IGUs) for vision glazing and for spandrel panel cladding. A risk for IGU in insulated spandrels is higher thermal stresses on the glass lites, compared to older approaches with single glazing. When ceramic enamel (frit) opacifiers are used, there is increased stress from solar absorption. Thermal stress is generally addressed by heat-treating at least the opacified lite. Multiple incidences of thermal stress-related fracture of ceramic enameled spandrel glass in North America, Europe, and elsewhere have shown that ceramic enamel weakens glass, reducing the added benefit of heat treatment, so there remains a risk of in-service thermal stress breakage.

This presentation will give examples of breakage, describe causes, show results of a test program that shows ceramic enamel reduces the strength of heat-treated glass, and describe options to control the potential for in-service breakage. The discussion will be of interest to building owners, designers, and builders considering the use of curtainwall and window wall systems with opacified glass.

George P. Torok, CET, BSS

Morrison Hershfield Corporation | Ottawa, Ontario

George Torok is a façade specialist in the façade engineering team of his firm’s Ottawa, Ontario, office. He provides specialist consulting services to architects, building owners, developers and builders, and façade system manufacturers across Canada and the U.S. He has over 30 years of experience in new building enclosure design and construction and existing building performance failure investigation, rehabilitation, and renewal. His specialty is fenestration systems, including windows, doors, skylights, curtainwalls, window walls, sloped glazing, and glazed architectural structures. He is a past president of the Ontario Building Envelope Council and the Building Envelope Council Ottawa Region, and a director of the Building Science Specialist Board.