Biogenic Materials for Mass Timber Wall Assemblies

Abstract

This Terminal Project investigates the potential of biogenic materials sourced from living organisms in the Pacific Northwest to enhance the sustainability of mass timber wall assemblies, specifically focusing on the insulation, the weather resistant barrier and the cladding materials. By developing a replicable model, I aim to extend its applicability to other mass timber production regions such as Australia/New Zealand and Japan. While it is recognized that mass timber sequesters carbon, many non-biogenic insulation and cladding products have been critiqued for their carbon impacts in their production, application, and lifespan (Abed, Joseph, et al, 2022). The study recognizes the carbon impacts of conventional non-biogenic insulation and cladding products, aiming to promote sustainable construction practices by exploring regionally available and novel biogenic materials, including those derived from older practices, waste products and invasive species. In the background research I explore what biobased materials are already implemented within the aforementioned regions and created a catalog of their properties and current uses. The project involves collaboration with the Material Composites Lab at Oregon State University to develop oriented-strand board cladding from wood fiber of invasive species like Western Juniper, a bioplastic weather-resistant barrier, and thermal/ acoustic insulation using agricultural wastes bound with mycelium. Insulation specimens include blue oyster mushrooms (Pleurotus ostreatus) and reishi mushrooms (Ganoderma lingzhi). Testing evaluated the thermal and acoustic properties of these mycelium panels as compared to commercially available biobased materials. Testing was performed on sample mass timber wall assembly mockups in the small acoustic testing chamber at the Energy Studies in Building Laboratory in Portland and in a fabricated thermal hotbox I made using ASTM standards to guide the construction. The assemblies, made from a 32”x 32”, 3-ply cross laminated timber (CLT) panel, that was splined together from smaller pieces, for replication of typical CLT panel connections incorporated the biogenic products outboard of the material to gather data on their viability as competitors for already commercialized biogenic materials, namely STEICO flex at 2”(50mm) wood fibre insulation. The goal is to develop a sustainable model that addresses regional challenges posed by invasive species, promotes the use of locally sourced bio-based materials, and revives traditional building practices, thereby advancing mate- rial autonomy and sustainable practices in the construction industry.