The impact of acoustics on human productivity in commercial and industrial buildings is profound. Studies such as one published in Electronic Physician have shown that there is a direct and significant association between levels of sound present in an environment and the quality and length of human output.1 Additionally, both the U.S. Environmental Protection Agency and the Occupational Safety and Health Administration (OSHA) have published requirements and standards for maximum noise levels in interior spaces, recognizing sound as a significant environmental factor that affects our health. Metal building insulation (MBI) plays a critical role in both the thermal efficiency of a structure as well as its acoustical performance.
Table courtesy NIA
Due to its porous nature, MBI is an excellent absorber of sound. According to the North American Insulation Manufacturers Association (NAIMA), MBI can reduce noise levels in a building by up to 5 to 6 decibels (dB).2 In addition to decreasing outside noise transmission to the interior environment, MBI also reduces noise created inside a building. Sound abatement properties may seem like an added benefit, but MBI becomes a crucial building material for applications in which sound potentially reaches dangerous noise levels, such as compressor stations and other buildings with loud, heavy machinery.
Table courtesy NIA
When it comes to assessing acoustical performance, sound transmission class (STC) ratings are important. Intended to demonstrate the amount of sound that can pass through an assembly, STC ratings have been utilized for many years and are based on speech sounds. The higher the STC value, the better a construction reduces sound transmission. The average metal building ranges from a low of about 20 to a high of 55.3
In addition to STC ratings, there are three important fundamentals to sound transmission:
- Decibels (dB), which is a measurement of how loud a noise is.
- Sound transmission loss (STL), which is the ability of a wall or roof to reduce the amount of sound transmitted. STL is calculated as the dB difference between the two sides of a wall or roof.
- Frequency, which is quantified in Hertz (Hz), is the measurement of a tone. When conceptualizing frequency, it is helpful to think of a musical instrument. High-tone instruments have a 2,000 Hz range, and low-tone instruments have a 29 Hz range.
Table courtesy NIA
Another important sound transmission assessment is the concept of noise reduction coefficient (NRC) ratings, which measure how well a material absorbs sound. NRC ratings range from 0 to 1, with 0 indicating no sound absorption and 1 indicating 100 percent sound absorption. For example, a 0.85 rating equals 85 percent sound absorption.
Building codes should also be part of the acoustics conversation, as newer energy codes require more insulation in metal buildings than ever before. Gone are the days of installing 152.4 mm (6 in.) R-19 roof insulation and 101.6 mm (4 in.) R-13 wall insulation on all projects. Today, high R-value insulation systems have become standard in many climate zones, meaning thicker rolls of fiberglass—and more of them—are installed in roofs and walls. Fiberglass is the most common MBI material choice for a variety of reasons, including ease of installation, low installed cost per R-value, excellent thermal
Table courtesy NIA
performance, and superior acoustical properties. The greater thicknesses of fiberglass required by today’s energy codes lead to better overall acoustical performance (see Figures 1 and 2 ).
Conclusion
Pre-engineered metal buildings are known for their durability, versatility, and economic value, and they represent a significant portion of new commercial and industrial construction in the United States. However, as with any construction type, metal buildings pose their own unique set of challenges. At the top of that list is noise transmission, which can be addressed with the right amount of NAIMA 202-certified fiberglass.
Notes
1 Read more on the impacts of sound exposure: Khajenasiri F, Zamanian A, Zamanian Z. The Effect of Exposure to High Noise Levels on the Performance and Rate of Error in Manual Activities. Electron Physician. 2016 Mar 25;8(3):2088-93. doi: 10.19082/2088. PMID: 27123216; PMCID: PMC4844473.
2 Learn more with the NAIMA’s resource: “Insulation Facts #58: The Facts About the Acoustical Performance of Metal Building Insulation,” NAIMA, Pub. No. MB315 4/01.
3 Learn more with the NAIMA’s resource: “Insulation Facts #58: The Facts About the Acoustical Performance of Metal Building Insulation,” NAIMA, Pub. No. MB315 4/01.
This article was written by a task force from the National Insulation Association’s (NIA’s) Metal Building Laminator Committee. The member companies that make up this committee include Bay Insulation Systems, Inc. (www.bayinsulation.com); DAW Construction Group, LLC (www.dawcg.com); The E.J. Davis Company (www.ejdavis.com); International Insulation Products, LLC (www.iiproducts.com); L&L Insulations (www.llinsulation.com); Silvercote, A Service Partners Company (www.silvercote.com); and Therm-All, Inc. (www.therm-all.com).
This article was reprinted with permission and was originally published in the September 2024 issue of Insulation Outlook magazine, copyright © 2024 National Insulation Association (NIA), all rights reserved. Since 1953, NIA has been the voice of the insulation industry and is dedicated to keeping the commercial and industrial insulation industry up to date on the latest industry trends and technologies. For more information, visit www.insulation.org or email niainfo@insulation.org. Learn more about metal building insulation at www.insulatemetalbuildings.org.
