15 Aug 2018 BC Building Code: BKL Interprets Acoustical Changes for Design Professionals
In March 2019, BKL’s Phil Miville-Deschênes presented on the acoustical guidelines of the 2018 BC Building Code before members of Engineers Geoscientists British Columbia and the Architectural Institute of British Columbia during a joint meeting in Vancouver. Backed by a bounty of slides, Miville-Deschênes reviewed the latest updates to section 5.8 Sound Transmission of the Code and interpreted their significance for building designers.
Notably, he addressed the new code’s requirements for protection from airborne noise, measured by the apparent sound transmission class (ASTC), and explained how this change differed from past iterations that set criterion for sound transmission class (STC). Miville-Deschênes showed the group how STC testing, which accounts for direct noise transmission only, is not as accurate as ASTC testing, which includes direct transmission paths, as well as indirect paths—that is, noise travelling around a partition via adjoining walls and ceilings, ducts, halls, windows, structural components, and more.
Noise moving along these paths, called flanking noise, has potential to affect occupants even when STC requirements are met. Hence the updates to the Code.
Three Ways to Demonstrate Compliance
The 2018 BC Building Code requires designers to demonstrate compliance with its requirements for airborne noise. Miville-Deschênes walked participants through the options for showing compliance—prescriptive procedures, field measurements, design procedures—and highlighted the pros and cons of each approach.
For instance, the easiest way to demonstrate compliance is through prescriptive procedures, that is, selecting existing partitions and junctions from tables included in the Code and ensuring they meet the acoustical criteria. While this approach is straightforward, it restricts designers to the exact assemblies and adjoining constructions specified by the Code.
On the other hand, field measurements are highly accurate and can account for any construction type, yet they’re limited to completed buildings. Miville-Deschênes emphasized that the best time to address flanking noise is during design stages, since post-construction remedial work is often more expensive.
Using design procedures, which involves calculating ASTC ratings for partitions, is an option to show compliance early in a project, and allows for deviations from listed assemblies like cross-laminated timber and modular systems. The downside is that this approach requires acoustical expertise and specific lab test data on the components of the assemblies.
Helpful Tips from a Working Acoustical Consultant
Miville-Deschênes also shared a few acoustical best practices, such as selecting 25 gauge steel studs over 20 gauge, and installing resilient channel correctly to avoid short-circuiting. Additionally, Phil discussed about recommended impact noise insulation criterion within multi-family dwellings.
He also discussed ways to control plumbing noise, proper electrical outlet alignment, and the importance of door seals. Then he reviewed a few case studies, identifying acoustical problems and solutions for each.
New Code. Better Acoustics
The new 2018 BCBC involves important changes that will encourage architects and developers to adequately address acoustics at the design stage. In the future, as more new buildings adhere to these guidelines, anyone living or working in a high-density building will benefit from these changes. To read more about flanking noise and the 2018 BC Building Code, check out this blog post.
Otherwise, if you have a building project on the go and want to learn more about demonstrating compliance, give BKL a call. By reviewing drawings, analyzing partitions, and recommending upgrades and mitigation solutions where necessary, BKL’s acoustical consultants can bring their expertise to your project and ensure it meets the latest guidelines.