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Advertising supplement provided by Marvin Windows and Doors

Layering and Laminating Glass

ASTM E 1425–91, Standard Practice for Determining the Acoustical Performance of Exterior Windows and Doors, establishes requirements for testing and rating acoustical performance of exterior windows and doors, regardless of their method or materials of manufacture. This practice requires concurrent testing of air leakage and operating force in addition to acoustical tests. This deals with the acoustical performance levels of exterior windows and doors only, and not openings between such assemblies and adjacent construction. It does not include roof windows, skylights, sloped glazing systems, or any interior window or door assembly.

ASTM E 1332, Standard Classification for Determination of Outdoor-Indoor Transmission Class, provides a single-number rating that can be used for comparing building facade designs, including walls, doors, windows, and combinations. It is designed to correlate with subjective impressions of the ability of building elements to reduce the overall loudness of ground and air transportation noise. It is intended to be used as a rank-ordering device.

Achieving the Best Rating

While windows and doors can add beauty to a structure and be an important source of natural light, they can also allow the transmission of damaging ultraviolet rays, unwanted solar heat gain, and noise. Fortunately, product modifications can reduce these intruders from entering commercial buildings. A general guideline is that windows and glazing systems designed to provide superior air and water resistance will also offer some level of sound reduction.

To determine noise reduction capabilities of acoustically improved windows and doors, use manufacturers’ acoustic data or seek independent third-party certification of this information.

Creating Air Space

Glass is a dense material with some inherent sound reduction properties and the thicker the glass, the greater those properties.

But simply increasing the thickness of a single window pane is not structurally or economically acceptable. So, creating air space between panes of glass has become a feasible and efficient way to buffer against sound and temperature extremes. In fact, air space between panes of glass is the most crucial factor in improving a window’s or door’s STC rating. The larger the air space the less sound is transmitted through the window and the more the STC rating improves.

Windows that offer high energy efficiency also typically provide a higher STC rating because air infiltration is the key factor in controlling energy loss and noise penetration. Generally speaking, if air can get through a window opening, so can sound.

Today the best air space for thermal efficiency is considered 5/8 inch so this is generally the maximum spacing you will find in commercially available products. To improve sound reduction, however, the air space should be increased beyond 5/8 inch to provide the optimum level.

The STC rating of the glass can also be improved by adding gases, such as argon, between the panes. The desired STC rating should first be determined for the end use application because certain gases produce greater sound transmission loss at high frequencies than do others.