FAQ - MISCELLANEOUS

From time to time, we compile some of the most frequently asked questions from our clients. We have organized those questions into the following categories:

1. Insurance & Tax discounts (read more)
2. Design characteristics (read more)
3. Testing & Permitting (read more)
4. Cost (read more)
5. Energy Efficiency (read more)
6. Miscellaneous (read more)
7. Technical (read more)

A Practical Approach to STC and OITC Ratings

Sound Transmission Class (STC)

Simple Definition: For STC ratings, a higher number is better. A higher number correlates to less sound passing through the window assembly. The STC rating is based on frequencies of speech and is most applicable to interior office environments where vocal noise is of importance.

Technical Definition: A single-number rating calculated in accordance with ASTM E 413 using sound transmission loss values. It provides an estimate of the sound insulation performance of an interior partition in certain common sound insulation problems. The frequency range used is typical of indoor office noises.

What the Numbers Mean: A generic single pane window will receive an STC Rating of around 25. PGT impact windows are rated between 25 and 38. The chart below shows the perceptible difference as the STC ratings increase or decrease.


                     *For further information go to www.stcratings.com

Outdoor-Indoor Transmission Class (OITC)

Simple Definition: For OITC ratings, a higher number is better. A higher number correlates to less sound passing through the window assembly. The OITC rating is based on frequencies of traffic noises and is most applicable to exterior windows, where traffic and airplane noise is of importance.

Technical Definition: A single-number rating calculated in accordance with ASTM E 1322, using values of outdoor-indoor transmission loss. It provides an estimate of the sound insulation performance of a façade or building elements. The frequency range used is typical of outdoor traffic noises.

What the Numbers Mean: A generic single pane window will receive an OITC rating of around 18. PGT impact windows are rated between 22 and 32. The chart above, although specifically used for STC, can be used in principal to depict that perceived noise will considerably decrease by moving toward a higher OITC rating.