A mere 20 years ago, the idea of using glass to protect buildings from hurricanes might have raised a few eyebrows. Many would have scoffed at the idea of using colored glazing as a design element, or using glass to dampen unwanted environmental noise from the interior of a building.
Today, post-hurricane rebuilding efforts drive sales of impact-resistant glass, color trends continue to be a significant market driver for decorative glazing design, and environmental noise pollution fuels the demand for acoustic glass. As the construction industry grows aware of the possibilities of laminated glass, emerging technologies make it easier and more affordable to incorporate glazing systems into residential and commercial projects.
Laminated glass is not a new concept. The idea of laminating a polyvinyl butyral (PVB) interlayer between two layers of glass has been around for almost 70 years, and its use has been mandated in automotive windshields for more than 60 years. What is new are the unique uses and enhancements for laminated glass.
Powerful Protection
The devastating hurricanes of the past five years underscored the need for buildings to withstand the forces of Mother Nature. Evacuation has long been advised as the safest way to survive a hurricane; however, Hurricane Katrina was a grim reminder that evacuation is not always possible. With thousands of people potentially in the path of a storm, it is critical for essential facilities, such as storm shelters, hospitals and police stations, to be able to withstand the weather.
A glazed opening is generally considered the weakest part of a building. In a hurricane, high winds and complex pressures exert tremendous force on the exterior envelope of a structure. Even a small break in that envelope, such as a broken window, allows pressure, wind and water to enter. While wind and water can wreak havoc on a building’s contents, interior pressure can cause severe structural damage, potentially blowing the roof off and the walls out.
Laminated glass made with PVB interlayers in a properly designed and tested framing system can be an important element in protecting the building envelope. If the glass is impacted—even by debris blown at hurricane-force wind speeds—it may crack. However, the interlayer keeps the glazing intact, which helps keep it in the framing system and prevents debris from penetrating the building and entering the structure.
Many contractors working on projects in hurricane-prone areas are familiar with the large missile impact test that requires firing a 9-pound two-by-four at 50 feet per second (fps) toward designated areas of a window to demonstrate impact resistance. ASTM E 1996 labels this large missile impact test a Level D test.
However, another category listed in ASTM E 1996 requires an even higher functionality of performance called Level E. ASTM created Level E to ensure the safety of essential facilities that must remain functional during a storm. Level E testing requires the 9-pound two-by-four to be fired at 80 fps—that’s 50 mph rather than 34 mph for Level D.
Until recently, meeting Level E meant choosing from less-than-optimum options: polycarbonate, double-laminated insulating units or no window openings at all. With polycarbonates, costs and long-term aesthetics can be an issue. Double-laminated insulating configurations can more than double the cost of standard laminated glass and may require custom framing systems to support the weight and thickness of two lites of laminated glass. And of course, windowless bunkers are not ideal in terms of design.
Today, a high-performance interlayer that meets Level E is available in a single lite of laminated glazing. The new solution eliminates the need to use a double-laminated insulating glazing system, making hurricane protection more affordable and easier to incorporate. The glass looks and functions like a single piece of ordinary glass, but is stronger than some burglary-resistant products on the market.
The Sound of Silence
Significant progress also has been made using laminated glass as an acoustic barrier. Rush-hour traffic, airplanes, construction equipment and blaring music all contribute to the accelerating noise pollution in urban environments. The Environmental Protection Agency’s Office of Noise Abatement and Control notes that “noise constitutes a real and present danger to people’s health and can produce serious physical and psychological stress.” With that in mind, improving the ability of windows to resist the passage of airborne sound into building spaces is a high priority for architects and builders.
Previously, glass was considered a weak acoustical point of a building, but new technologies make glass a powerful noise abatement tool. Windows made with an acoustical interlayer reduce noise with the same—or thinner—glass thicknesses as tempered glass or laminated glass made with a standard PVB interlayer.
A multilayer acoustical interlayer, which consists of a layer of special acoustical PVB sandwiched between two layers of traditional PVB, suppresses the coincident effect that prevents glass from blocking sound. It delivers up to 10 decibels of noise reduction (transmission loss) in the critical frequency range of 1,000 hertz to 5,000 hertz (the range in which most speech is heard and understood), compared to laminated glass made with standard PVB.
Additionally, the acoustical interlayer meets all U.S. federal safety glazing requirements and can be used in areas deemed as hazardous locations by the building code, such as doors, skylights, and overhead and sloped glazing.
Designing with Color
Every year, colorists predict the colors that will dominate everything from clothing to cars. These prognosticators try to read the mood of the country and note trends that will influence color direction. According to the Color Marketing Group (CMG), a not-for-profit international association for color design professionals, today’s hottest color trends are influenced by two major issues: the economy and optimism for the future.
Color trends are significant market drivers for the glazing industry. Custom color interlayer systems in laminated glass can produce a broad spectrum of colors and moods that are unachievable using stock selections of glass. Interlayers can be combined to produce transparent, translucent or opaque color options to help create unique tones and intensities—with all the performance benefits of laminated glass, including safety, security, sound reduction and structural integrity.
Curtainwalls, atriums, skylights, partitions and conference rooms are just a few applications where laminated colored glass allows architects and builders to create expressive and beautiful structures.
According to CMG, some of the most noteworthy color trends for 2009 include:
- The right white. Today, white is more than just a blank slate on which to showcase color. It can complete a design through balance and strength. In both interior and exterior applications, white interlayers allow for total opacity for private settings or translucent designs to let the light shine in—plus greater flexibility between these extremes. White interlayers can be used alone as a single layer in a glass laminate, or combined with colored interlayers to achieve two different colors of glass in a single unit (e.g., white on one side and a tranquilizing blue on the other) to allow designers to create original, sometimes reversible, designs.
- The new hue of blue. Going green has been one of the hottest trends of recent years and has been represented by various shades of green. This year, the new green message is being symbolized through greens that are grayer and bluer, trending away from yellow-based shades of green. An entire range of blue hues, from watery blues to sky blues, will now represent going green.
- Vivacious yellows. Look for bright cheerful yellows as the newest accent color to represent the energy needed to rebuild the economy.
Glass BreakthroughsThe use of laminated glass in building applications is clearly gaining momentum. The growing adoption of high-performance glass for protection from Mother Nature and man-made environmental noise continues to be fueled by technological breakthroughs in the glazing industry. Innovations in colored interlayers provide greater design versatility while retaining the benefits of standard laminated glass. Laminated glass has changed the construction landscape and the style of modern architecture today—reinforcing what a long way the industry has come.