Volume 47, Issue 6 - June 2012
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Is the Acoustic Glass Market Making More
Laminated glass suppliers have noticed a growing demand for their product for safety and decorative applications in recent years. Today, more designers than ever are asking about another property of laminated—sound reduction—and in more cases are going beyond a standard PVB interlayer to specially designed acoustic glass products.
Architects Ask for It
Schools and university jobs as well as commercial buildings that are near airports are beginning to focus on acoustical performance as a way of reducing sound transmission into the building, according to information from Viracon in Owatonna, Minn. Company representatives see a greater focus than ever before on incorporating sound transmission performance into building projects.
“Schools, hotels and hospitals are all perfect applications for the use of acoustic laminated glass,” adds Aimee Davis, architectural business manager, Americas, for Solutia in St. Louis. “Studies have shown that students do better in quiet environments, patients in hospitals heal faster and of course, guests at hotels all appreciate a quieter room.”
“We are seeing a higher demand and request for noise reduction glass both in commercial and residential applications,” reports Ken Schraufnagle, key account manager for Pilkington North America in Toledo, Ohio. “There are many types of applications calling for [acoustic glass], such as sound studios, hospitals barriers between office and factory, noise reduction walls on highways, airports and many urban applications as it relates to traffic and subway noise.”
How It Differs from Laminated
Andy Russo, residential segment director for Guardian, explains, “An acoustic laminated glass utilizes an acoustic PVB that combines two layers of standard PVB with a unique third layer. This special layer targets sounds within the 1,000 to 3,000 Hertz range. Acoustic laminated glass can provide a 10-decibel noise reduction in this range and a perceived 50-percent reduction of noise compared to standard laminated glass.”
As Schraufnagle points out, this specially designed PVB offers “enhanced sound reduction,” while also offering those standard benefits of laminated glass, such as impact resistance.
“As the world becomes a more congested place, so will the need to silence the outside world. Unlike ever before, laminated glass can now be produced in a variety of colors, or with digital imaging making the product both functional and aesthetically appealing to architects,” comments Jon Hughes, director of marketing and programs for AGC Glass Co. North America in Alpharetta, Ga.
Hughes adds that, in addition to using acoustically designed interlayers, fabricators are “combining specific thicknesses of glass and interlayer material into a single composite, or in combination with an air cavity, it is possible to ‘tune’ the glass to reduce the transmission of specific frequencies.”
“There are other glass/IG parameters that can be changed to also help reduce sound transmission and the window framing needs to be factored into the result,” Di Cesare adds. PPG published a technical document, Glass Acoustical Performance, to guide its customers on this point. Perhaps most importantly, the document reminds fabricators, “It must be remembered that the sound transmission class (STC) or outdoor-indoor transmission class (OITC) rating of a glass product does not represent the rating of the glazing system.”
The STC rating is applicable to interior building partitions and viewing windows where the sound source is human speech and/or office equipment. The OITC rating is applicable to exterior walls, including doors and windows, where the sound source is due to vehicles. These numbers are measured in accordance with ASTM E-90-02, Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements; the higher the number, the better the sound dampening.
Cost and STC Claims
Brown, for one, doesn’t see acoustic glass getting hotter in the commercial market—but sound dampening is being more consistently listed as one of the many reasons designers opt for a laminated product.
“I do see more and more requesting/wanting more noise reduction, but very few are willing to pay the premium required,” Brown says. “[Designers] do use laminated glass; that demand is rising, but to claim it is for acoustic reasons would be an overstatement. They may choose laminated for assorted reasons, including acoustic, but as with too many things, the costs override many other decisions and preferences. There are many reasons to select laminated—so many do—and most will claim it is for acoustic reasons, even if it is way down the list of why it was selected.”
Since acoustics is growing on the list of requested properties, however, designers and other specifiers are learning more about noise ratings, and the misconceptions that come with STC ratings.
Like Di Cesare, Brown cautions, “Glass STC numbers are pretty well established. They are the same, year in and year out, always getting the same STC value for the same glass product. However, some window companies abuse that—too often claiming that if laminated gets an STC of 35, then their window gets an STC of 35. This is almost never the case. Windows rarely get the STC values as good as the STC values of the glass itself, especially true of operable windows. Most window companies offer various glass configurations for each window model, to be able to get better STC values when demanded. Glass and window companies may list, but do not push, STC values. Unlike constantly improving/changing energy values, STC values are amazingly static.”
Megan Headley is special projects editor for USGlass magazine. She can be reached at email@example.com.