By Michael Miller, assoc. AIA
The growing focus on climate change is prompting architects and their partners to re-evaluate traditional strategies and materials in search of opportunities to mitigate the environmental impact of buildings. While glass has proven instrumental in reducing facilities’ electrical demand and mechanical loads, it remains an energy-intensive material to manufacture. As a result, manufacturers have invested in a range of solutions to reduce how far they transport materials, incorporate more recycled content into their products, and adopt renewable energy solutions that power manufacturing processes, among other strategies.
Despite these advances, fire-rated glazing products present a unique challenge for specifiers searching for versatile, durable materials to lower a building’s carbon footprint. Conventional fire-rated glazing provides significant advantages alongside its invaluable passive protection properties. Yet the highest-rated products capable of achieving 120 or even 180 minutes of fire resistance generate significantly higher carbon emissions than their thinner, lower-rated counterparts. Moreover, some conventional fire-resistant products have achieved their properties through chemistries that limit recyclability, adding to their cradle-to-grave environmental impact.
Historically, fire-rated glazing is not a fast-evolving category; but when innovation happens, it is often groundbreaking. The new generation of intumescent glazing introduced this year is no exception. By delivering the same essential fire resistance in an unprecedented, dematerialized configuration, architects can more effectively protect people and the environment.
A brief history of fire-rated glazing innovations
When wired glass was introduced in 1892, it presented a novel solution for providing visibility without sacrificing safety. In the earliest iterations of fire-protective glass, wire mesh was embedded within plate glass during manufacturing. This wire held the glass together in the event of breakage. For decades, traditional wired glass was the only glazing type that could pass North American fire testing standards.
Ceramic glazing was not introduced as a wire-free alternative until the early 1980s. Through a heat treatment process, traditional glass is transformed into a crystalline material that can withstand exposure to a wide temperature range without risk of thermal expansion.
This new generation of fire-rated glazing materials in architectural applications addressed the single biggest problem with wired glass. While wire could hold sharp annealed glass shards together in a frame, the wire itself could cause serious injury or even death in the event of human impact. By eliminating this risk, ceramic glazing allowed building owners and occupants to enjoy the many benefits of glass more readily, including access to natural daylighting and visibility into egress passages in the event of a fire.
However, ceramic glazing had its limitations. While ceramic glazing protects building occupants from the spread of smoke and flames, it allows the transmission of dangerous radiant heat. This significantly limits its versatility in architectural applications. While fire-protective ceramic glazing continues to be the dominant product type for fire-rated doors, sidelite, transom, and window assemblies, it cannot be used in large spans and certain applications, such as interior stairwells and exit corridors. Since ceramic glazing allows for the passage of radiant heat, designers must also specify the use of active fire suppression technologies, such as sprinklers, to provide comprehensive protection for building occupants.
This limitation prompted its innovation with the introduction of fire-resistive intumescent glazing.
Intumescent glazing, also introduced in the 1980s, marked the last revolutionary innovation in fire-rated glass. Typical intumescent glazing products consist of thin layers of a transparent intumescent interlayer sandwiched between pieces of tempered or annealed glass. When exposed to the heat of fire, the interlayers react to form opaque, insulating layers. These layers prevent the spread of smoke and flame as well as the transfer of radiant heat, providing a versatile fire-resistant solution. Since the heat will eventually degrade the intumescent interlayer, higher fire ratings are achieved by applying multiple layers of glass and interlayers.
For decades, intumescent glazing solutions have given architects design versatility. This class of fire-resistive glazing can be specified in virtually any application for up to 180 minutes of fire and heat protection.
Climate change challenge demands new fire-rated solutions
Architects today face an entirely new set of challenges. Chief among these is the built environment’s inescapable impact on climate change. The path to decarbonization demands new design strategies and specification of new construction materials.
Glazing materials have adapted to this challenge. Today’s energy-efficient products allow architects to maximize natural daylighting deep within buildings while reducing heat transmittance. The right combination of solar design strategy and glazing materials can significantly reduce a building’s electricity demand and mechanical loads, even in fire-rated and other specialty applications.
Manufacturers also address the embodied carbon generated through glass’s energy-intensive manufacturing process. As with any building product, more material equates to more embodied carbon. In the case of fire-resistive intumescent glazing, each added layer of fire protection carries an environmental toll. In the case of one fire-rated glazing product, a 60-minute-rated material includes 58 kg/m2 (127 lb/sf) of raw material compared to 110 kg/m2 (242 lb/sf) raw material for an equivalent 120-minute fire-rated product. With a global warming potential of 7.24E+01 kg CO2 equivalent (CO2e) per square meter, any reduction to raw material and subsequent processing provides a significant opportunity to minimize a building’s environmental impact. Now, fire-resistant glass can benefit from the glass industry’s decarbonization efforts.
Transformative fire-rated glazing redefines protection
With decarbonization among the largest looming challenges facing the AEC industry, fire-rated glazing manufacturers set out to develop a new solution to reduce their environmental impact. As of this year, specifiers can now select a next-generation intumescent glazing product with less embodied carbon. This product features only a single chamber containing a heat-absorbing polymer interlayer between two 6-mm (152-in.) sheets of tempered glass, whether the rating is 45 minutes or 180 minutes. The result is a fire-resistive material with up to 35 per cent less embodied carbon than traditional fire-resistive glazing systems. This introduction marks the first potentially industry-transforming innovation in 40 years.
This single intumescent chamber, combined with the least amount of glass seen on the market, has created a solution that has demonstrated higher levels of environmental stability than conventional fire-resistive glazing in testing. Due to its advanced environmental stability, building owners can reduce the future cost of replacement glass materials by disposing of fewer lites of glass over the course of a building’s life cycle.
When it does come time for disposal, this new intumescent glazing technology delivers a significant additional advantage. The product incorporates no carcinogenic or otherwise hazardous materials, improving the chemistries of certain conventional fire-resistant products in compliance with the gold star of environmental regulations, the European Union’s Registration, Evaluation, and Authorisation of Chemicals (REACH) regulations. Enhancing time-tested chemistry means that this improvement in fire protection is now better able to protect the environment.
Breaking barriers to innovation
The fire-rated glazing industry has seen firsthand that innovation can take hold slowly. In 2002, an epidemiologic study of Consumer Product Safety Commission (CPSC) injury data determined that 90 per cent of the 2,500 glass door injuries tracked each year in the CPSC system involved wired glass. Despite decades of evidence that wired glass caused as much harm as it prevented—and that a safer fire-rated glazing alternative had been available since the 1980s—it was not until 2006 that wired glass was removed from the International Building Code (IBC), and not until 2017, when it was finally removed from the Canadian General Standards Board’s safety glazing standard, CAN/CGSB-12.1, Safety Glazing.
This new intumescent glazing product may be easier for architects to adopt. As the newest iteration of an already widely used product, there are no building code hurdles for architects to overcome prior to specifying it. Moreover, the thinner profiles and greater variable light transmittance give architects greater design freedom.
This product’s versatility also significantly simplifies the work of specifiers. Since this new class of product has the same fire ratings as the walls into which it is installed, there are virtually no limits as to how it can be used. It can be specified for any application where architectural glass is found: interior partitions, exterior windows and walls, flooring, and more. It can be easily integrated into multifunctional units with a range of security and other performance characteristics. In some cases, it may even reduce reliance on redundant fire suppression systems.
Glaziers are juggling several opposing factors that can make it difficult to find and use paths and products that are better for the environment, from cost-cutting building owners to limited availability of products and even the preferences of designers. Standards such as LEED and WELL are cutting through those difficulties, as are regulations and building codes that mandate the use of sustainable products in construction projects. The benefits and value of this new class of products become even more tangible when it comes to transportation and installation of a thinner, lighter product.
The drive to develop a more durable, sustainable material may have led to this evolutionary leap in fire and heat protection, but the result has raised the bar for form and function even further. The newest generation of intumescent fire-resistive glazing reduces design barriers and simplifies the process of searching for safe, secure materials to bring the design advantages of glass to life.
Author
Michael Miller brings more than a decade of expertise to his role as the North America sales manager for Vetrotech.com/en-us, specializing in fire-rated glazing. His background spans commercial construction, real estate development, technology startups, and government, and he holds degrees in architecture and political science from Ball State University.
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