Acoustic Performance in Windows
According to the U.S. Census Bureau, noise is the number one complaint people have about their neighborhoods. Using one of JELD-WEN's sound-reducing glass options allows homeowners much quieter living spaces.
Having covered the basics of acoustics in An Introduction to Sound Control, let’s take a look at window options that affect acoustic performance. Specifically, we’ll review the combinations of components and window types that are optimal for sound control.
For practical solutions to sound control, dual-pane windows are nearly always the best choice. They are cost-effective, energy efficient if ordered with Low-E glass, and retain the aesthetic beauty and functionality windows were designed for. A standard dual-pane window carries an STC rating of around 27, but requesting the appropriate options can boost that value up to around STC 34.
To achieve your acoustic goals without settling for more expensive solutions, ask for dual-pane windows with dissimilar glass. While standard glass units consist of two panes that are the same thickness, dissimilar glass refers to a window with two panes of glass with different thicknesses. For instance, one pane might be 1/8" and the other 1/4".
Each pane in a dissimilar glass unit blocks different sound frequencies. One pane targets lower frequency sounds like a neighbor’s stereo or airplane noise. The other pane targets higher frequency sounds like screaming. The result is sound control over a greater range of frequencies and a significantly higher Sound Transmission Class (STC) rating than a window with standard dual-pane glass.
In fact, dual-pane windows with dissimilar glass can achieve STC ratings nearly as high, if not as high, as triple-pane or laminated glass. At JELD-WEN, for example, we offer a variety of dissimilar glass combinations on our Vinyl windows that carry up to an STC 34 rating. Consider that an average exterior wall of a stick-built home has an STC rating between 34 and 38. An STC 34 brings the windows up to the level of most of the outside envelope of the home. Anything higher is impractical because, while sound might not enter via the windows, it will just as easily enter through the lower-performing exterior walls.
Clearly three panes of glass are better than one, right? Not necessarily. In many cases, a triple-pane window has smaller air spaces between the panes of glass. These smaller airspaces are less than optimal for sound control and often create a reverberation in the sound waves that amplifies the sound level and cancels out any beneficial effects a third pane of glass provides. Our Research and Development team here at JELD-WEN has shown, through past testing, that an average triple-pane window has an STC rating about that of a dual-pane window with dissimilar glass.
The main purpose for laminated glass is to guard against high wind environments where impact resistance is required. As with triple-pane glass, laminated glass reduces the airspace and doesn’t tend to perform much better than a dual-pane window with dissimilar glass. In some cases, however, laminated glass can offer a slight (around one point) STC improvement. If meeting an architectural specification that requires, for example, an STC 35 instead of the STC 34 you might meet with dissimilar glass, laminated glass may be necessary. Be advised, though; laminated glass can add between 30 percent and 50 percent to the cost of the window, making it a fairly impractical solution from a cost perspective.
Window materials and operating types
Vinyl and wood windows, in general, perform well when it comes to blocking sound. Aluminum conducts sound and should typically be avoided as a solution to sound control.
Windows with a higher glass-to-frame/sash ratio are likely to perform better, especially if the glass in the window is designed to achieve a higher STC rating. For this reason, casements, awnings and fixed windows are the ideal operating types.
Air infiltration also plays a big role in acoustics. The tighter the window, the better it performs. In general, those same window types (casements, awnings and fixed) tend to be more airtight in their design.
Higher STC rated products
When the entire structure is engineered for sound, specifying a dual-pane window may not be sufficient, even with dissimilar glass. In that case, look for windows designed from head-to-toe for sound control. While this may mean double-sashed or 4-track window systems or storm window applications that are bulky and less than aesthetic, solutions like this can achieve STC ratings up to 40 and higher.
In conclusion, given the state of today’s technology in the window industry, practical solutions to sound control can be easily achieved with the right combination of options in dual-pane windows. And recommending or specifying dual-pane acoustic windows has additional benefits you may otherwise lose with triple-pane or windows with laminated glass. Most notably, aesthetic and functional attributes tend to decline as a window gets heavier and bulkier.
For comprehensive sound control information about JELD-WEN products, download Technical Acoustic Documents.