Abstract
Exterior building envelope walls with rainscreen cavities are now required by British Columbia building codes. The introduction of the rainscreen cavity and optional external thermal insulation can alter sound transmission loss and consequently affect indoor sound levels in single and multi-family wood-frame housing. In this study, 57 exterior wall assemblies were built and acoustically evaluated using a hybrid sound intensity technique. The variables investigated were cladding material (vinyl, fibre cement board, and stucco), exterior insulation (mineral wool and XPS), exterior insulation thickness (1½" and 3"), cladding attachment type (resilient and non-resilient), and rainscreen cavity width (3/8" and 1"). The sound transmission class of the tested wall assemblies ranged from 37 to 52; the outdoor-indoor transmission class rating ranged from 26 to 37. Results indicated that the selection and the combination of the material layers were fundamental to sound transmission loss performance. Cladding material and cladding attachments influenced sound transmission and resulted in a broad range of overall performance. The split insulated rainscreen cavity wall assemblies presented higher transmission loss than single insulation walls, provided that the exterior insulation had sound absorbing properties. The best performing wall assemblies generally have high mass cladding, resilient cladding attachment, and 3" mineral wool exterior insulation (in addition to the interior cavity insulation). Given the research outcomes, in denser and noisier urban areas, a building envelope professional has additional options to design an exterior rainscreen cavity wall to meet thermal performance and acoustical criteria for exterior sound levels in wood frame buildings.