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Advertising supplement provided Solutia Inc. and Arch Aluminum & Glass Co.

Glazing selection

Whether single or double-glazing, the presence of one or two laminated components in a glass window or door can improve the acoustic performance of the glazing material by damping its resonance effects. In comparison, solid or monolithic glazing systems cannot as effectively control sound because of their reduced ability to screen certain frequencies of noises.

Monolithic glass (single thickness glass) has very low inherent damping because its transmission loss (TL) is affected by the mass of the glass and the bending frequency at various thicknesses. In order to get meaningful TL increases with monolithic glass, significant mass (thickness) must be added.

Typically the highest acoustical rating that can be achieved with a practically available monolithic lite is around 36 STC (12.7 mm [0.5 inch] glass). Double-glazed systems may offer an improvement over the monolithic systems, but the span of air space required to provide acceptable acoustical control introduces architectural design restraints as well as higher costs.

The installation of windows that provide an acceptable noise reduction involves first the assessment of the environmental noise and then the determination of the minimum acceptable window sound transmission class (STC) rating of weighted sound reduction index or Rw (the glass rating that is used in international and European standards).

Once a minimum sound reduction requirement has been determined, the next step is to use the information to arrive at an acceptable window glass configuration. This involves selecting or designing a glazing that has STC or Outside-Inside Transmission Class (OITC) values equal to or higher than the minimum required window performance level. The glazing selection would then be reviewed for other performance attributes such as safety, security, solar control, life cycle and aesthetics.

Laminated glass consists of a tough protective interlayer made of polyvinyl butyral (PVB) bonded together between two panes of glass under heat and pressure. Once sealed together, the glass “sandwich” acts as a single unit and looks like ordinary glass. Laminated glass made with a PVB interlayer is highly effective in reducing unwanted sound transmission and can be effectively used in standard window design.

Laminated glass with a polyvinyl butyral (PVB) interlayer provides a single unit system combining the density of glass with the sound absorbing characteristics of the PVB interlayer resulting in a single unit system that can provide the architect and specifier with a superior system for controlling unwanted sound.

For example, a 1/4-inch laminate (two lites of 1/8-inch glass bonded with 0.0300" PVB interlayer, nominal 1/4-inch overall thickness) has TL nearly equal the sound isolation provided by two pieces of glass 1/2-inch thick separated by 1/2-inch air space (1-inch overall thickness).