Window Sound Transmission Coefficient
Category : Replacement Windows
By Craig A. Shutt
*Window Sound Transmission Coefficient*
If your clients complain that they’re tired of hearing the next-door neighbor mowing his lawn at 7 a.m. Saturday or are sick of his barking dog, they’re offering you a great opportunity if you are up-to-date on the acoustic control benefits of new window designs and window-installation techniques. Window manufacturers are well aware of the increasing demand for enhanced window acoustics.
Two key factors affect a window’s sound transmission coefficient (STC): the window’s design and its installation, Head says. Windows, as with other materials, are rated with an STC, which indicates how well the window blocks sound waves. A typical double-pane window with 2 1/2-mil, single-strength glass provides an STC rating of about 28 to 32. The higher the STC number, the better the sound control. Airport locations often require windows with a 35 to 40 STC rating. The good news is that excellent acoustic control works hand in hand with high energy efficiency. The same air that brings in noise also brings in air that must be cooled or heated, reducing energy efficiency. When you select high performance windows that lower energy costs, you gain the added benefit of less noise intrusion, Head explains. Proper sealing during installation is also vital. The best way to reduce noise infiltration is through a high-quality weatherstripping system, Head says, since the weather stripping is usually the weak link in the system. “It’s easier to penetrate than wood or glazing. Weatherstripping both the frame and the sash creates additional points of contact to reduce infiltration of anything — dust, water, air, sound.” Window manufacturers are working to create window designs that do more to foil noise infiltration. The key is to disrupt the sound waves as they pass through the window. This can be done by using different thicknesses of glass, creating different vibrations that deflect the waves. Additional layers, such as with a tri-pane system, also can be beneficial. Vinyl-window makers achieve this acoustic disruption by creating baffles and catacomblike systems in their hollow extrusions; that also creates thermal breaks that aid energy efficiency.
Laminated glass may aid noise reduction because it is a thicker product. The additional cost for laminated glass is significant, but the product also provides enhanced safety levels.
Noise is encroaching more and more, Head adds. “We’re becoming more urban, with higher density in home construction. That creates more need for us to block out neighbors and traffic.” Selecting windows with higher Sound Transmission Coefficient ratings and insisting on tighter seals during installation can go a long way toward keeping out this noise pollution.