Replacing wired glass

Improvements during the past few years in glass-ceramic technology mean that architects and glaziers have an alternative to wired glass as a glazing material for fire-rated doors and windows. Glass-ceramic products enable architects and glaziers to design and build fire doors and windows that are clearer, more aesthetically pleasing and safer.

Fire-rated door and window assemblies are essential to fire safety. They protect openings and prevent fire from quickly spreading throughout large buildings. An essential component in these assemblies is the glazing material, which has to be fire-protection rated and tested according to appropriate standards. For a long time, wired glass was the major glazing material used in these assemblies, since it met North American fire test standards, including the required hose stream test. The wire mesh in wired glass keeps the glass from falling out of the opening, even if the glass cracks during a fire.

Enter glass ceramics
Glass ceramics meet North American fire test standards thanks to their material properties. The high temperature resistance and zero-expansion properties of glass ceramics allow even large panels to pass fire and hose stream testing safely.

Though wired glass is still strong when it comes to fire, it is weak when it comes to force. The wire mesh built into the glass makes it look safe, but does not enable standard wired glass to meet the Consumer Product Safety Commission’s impact safety standards. Actually, it makes it less impact-resistant than other types of glass of equal thickness, meaning that it is more likely to break if someone falls into or against it. When broken, the wires in wired glass often cause serious injuries. However, some manufacturers have reinforced standard wired glass and now offer versions coated with film that meet the CPSC Cat II test and laminated versions that meet the CPSC Cat I test.

In 2003, partially due to the introduction of glass-ceramic alternatives to wired glass, the International Code Council of Washington, D.C., revised the International Building Code, and removed a key exception for wired glass. With this revision wired-glass not meeting the CPSC impact safety standards could no longer be used in hazardous locations in schools, daycare centers and athletic facilities. Just last year, the code was revised further, mandating that glass not meeting the CPSC impact safety standards could no longer be used in hazardous locations in all types of construction. The ICC recognized that with the introduction of fire-rated glass-ceramic products, wired glass was no longer the only option for fire-rated doors and windows.

Ceramics more attractive
States, cities and other jurisdictions are adopting the 2006 IBC revisions for new buildings. Many schools, hospitals and other public facilities are making their buildings safer by replacing wired glass with fire-rated, impact-resistant glass-ceramic products. In addition, architects now realize that glass-ceramic products give them the opportunity to design facilities with more attractive fire doors and windows. This has all led to a growing demand for fire-rated glass ceramic, which has in turn prompted several innovations in the market, as manufacturers seek to make their glass-ceramic products look, feel and work better.

For instance, until recently fire-rated glass ceramic had a yellow-brown tint. While this tint is minimal, some architects found it unattractive or felt it detracted from aesthetic qualities of their design. Schott researchers have found a way to adjust the mix of raw materials it usually uses to make glass ceramics. This development enables Schott to offer architects its Pyran Crystal suite of glass-ceramic products, which have a more neutral tint.

Leading glass-ceramic manufacturers, such as Technical Glass Products of Kirkland, Wash., and Vetrotech of Auburn, Wash., also are working to find ways to make glass-ceramic surfaces smoother. The surface of most fire-rated glass ceramic is slightly rough, similar to an orange peel. Until recently, polishing the glass ceramic was the only way to make this surface feel smooth. However, Schott researchers have discovered a way to alter the glass ceramic manufacturing process to produce a laminated fire-rated glass ceramic whose surface is almost indistinguishable from polished glass ceramic. Schott introduced this smooth fire-rated laminated glass product, Pyran Star L glass ceramic, at last year’s American Institute of Architects National Convention and Expo. Customer interest in the product is strong, particularly among architects who want a smooth and safe fire-rated glass for high-visibility areas.

Thanks to these and other glass-ceramic innovations, architects can now design facilities with fire-rated doors and windows that they don’t feel compelled to hide. Glaziers can provide their customers with lighter, more attractive alternatives to wired glass. And schools, hospitals and other public facilities can replace unattractive, non-impact resistant wired glass in their buildings with more attractive, impact resistant glass-ceramic products.

Despite the many advances already made in glass-ceramic technology, there is still room for improvement. Companies like Schott are currently investing in glass-ceramic research, trying to find ways to make fire-rated glass-ceramic even clearer, smoother and safer. Over the next few years, glaziers and architects can look forward to seeing the introduction of an array of new fire-rated glass-ceramic products.