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NRC testing and ASTC ratings
The National Research Council of Canada (NRC) is the federal government’s world-renowned research organization supporting innovation, the advancement of knowledge, and technology development. It recently tested multiple configurations of proprietary 15.9-mm (5/8-in.) noise-reducing, single-layer laminated drywall and noise-reducing interior stud-designed fibreglass insulation, offering 42 wood-frame and one CLT examples of ASTC- and STC-rated assemblies. Additionally, 22 steel-stud examples of ASTC- and STC-rated configurations of these materials were tested by NRC. All of these 65 examples received an ASTC rating of 47 or higher and STC 50, meeting or exceeding code requirements.
To comply with ASTC and STC requirements in the construction of mid-rise wood-framed and all types of high-rise structures, there are numerous options, such as assemblies employing a combination of laminated drywall, noise-proofing sealant, noise-proofing putty, and noise-reducing insulation to effectively reduce the transmission of airborne and flanking sound. For wood-stud assemblies (Figure 3), specifying such a system offers noise-reducing capabilities by dissipating sound and minimizing the transmission of noise through flanking paths to potentially achieve 54 ASTC and 54 STC ratings. For steel-stud assemblies (Figure 4), ratings of ASTC 48 and STC 50 are achievable.
With these systems, the specialized drywall means fewer layers than is required for a traditional gypsum system needed to meet ASTC standards. This results in less labour and faster construction, while also reducing material usage and reclaiming lost square footage. Further, the use of the proper noise-proofing sealants and putties help restrict the flow of air, reducing the risks of spreading fire and smoke between dwelling units.
The payoff of better acoustics and fire protection
Due to the link between the two, noise transmission is limited when the best available technology in fire prevention is used and vice versa. The myriad benefits when smart acoustic design and additional fire protection measures are incorporated in mid-rise wood-framed construction also apply to hospitals and schools.
Creating a comfortable acoustic environment in healthcare environments plays an important role in supporting safety, health, healing, and well-being for all occupants. Additionally, maintaining speech privacy in healthcare facilities helps reduce medical errors as it supports open conversations among patients. For example, Saskatoon’s Jim Pattison Children’s Hospital (Figure 5) makes use of a high-performance building envelope system along with interior acoustic assemblies for the comfort and health of patients and medical teams. Acoustic considerations include sealed electrical boxes, drywall joints, door penetrations, and floor junctions (Figure 6).
While the use of some of the necessary value-added materials may have higher initial costs, there is an overall cost savings through the recovery of usable space (Figure 7). For example, staggered stud walls are about 100 mm (4 in.) thinner than double-stud walls, thereby providing about 3.3 to 4 m2 (33 to 40 sf) of additional usable space. With approximate condo square footage costs of $500, this can be an average of $16,500 to $20,000 for an average-sized unit. (For more, see this author’s September 2016 Construction Canada article, “Implementing Smarter Sound Control Strategies.” Visit www.constructioncanada.net/implementing-smarter-sound-control-strategies.) The added bonuses of potentially achieving acoustic credits under programs such as the International WELL Institute and Leadership in Energy and Environmental Design (LEED) credits make this an even more attractive option. (In Part 3, “Wall Construction,” WELL provides credits for optimal performance by reducing air gaps and limiting sound transmission through properly sealing all acoustically rated partitions at the top and bottom tracks, staggering all gypsum board seams, and packing and sealing all penetrations through the wall. LEED v4 offers one or two credits in the Interior Environmental Quality [EQ] category’s Enhanced Acoustic Performance.)
As architects, engineers, legislators, building officials, and consumers look for affordable, more sustainable solutions with more healthy acoustics, but without compromising health and safety, there is no doubt mid-rise wood-stud and high-rise steel-stud construction will be increasingly popular solutions. Developers would be well-served to explore tested systems as options for commercial and residential projects and look to leading authorities such as the NRC to provide world-class research to support innovations. High-rise construction, hospitals, schools, offices, and other nonresidential projects will benefit from these additional steel-stud tested systems.
Conclusion
As more jurisdictions adopt and implement these new ASTC requirements, it has never been more important to take noise control measures into account. The additional benefits of better acoustic design add even more credence to the ASTC rating system. By making use of innovative technologies, designers/specifiers/developers can provide better fire safety and well-being for occupants and by extension, allow Canada to be a global leader in more innovative building system options.
Robert Marshall, P Eng., BDS, LEED AP, is a building science manager for CertainTeed Gypsum Canada. He has been appointed by the National Research Council (NRC) to the Standing Committee on Energy Efficiency in Buildings. Marshall can be reached via e-mail at robert.marshall@saint-gobain.com.
