Impact of species, coatings, and RH on microbial community structures within mass timber products

One of the advantages of mass timber buildings is the inherent biophilic nature of expressed wood structure. Interior exposed panels not only have a positive emotional impact on building occupants, but also have unseen physiological impacts on their health. This may be driven, in part, by the influence of mass timber to improve a building’s microbiome and increase moisture content of the air. Wood is a porous, natural material that can foster microbes on its surfaces. Many of these are structurally non-destructive and potentially beneficial to occupants which together shape the building’s microbiome to have a non-visual impact on the wellness of occupants. However, building surfaces are potentially also repositories for human-associated microbes, some of which could cause illness. Furthermore, wood appears to buffer indoor humidity, a result that has been shown to support human immune system health. The properties of interior surfaces and their impact on indoor air are important factors to consider affecting the longevity of hazardous bacteria, fungi and viruses in buildings and overall human immune system health. These properties are particularly relevant in light of the recent novel coronavirus outbreak. The use of natural materials, such as wood, might be an important strategy to reduce the spread of disease indoor by fostering beneficial microbes while also inactivating pathogens (through selective antimicrobial qualities) and support of human mental health (biophellia) and immune systems (humidity buffering).

Variation in wood chemistry and the addition of moisture-excluding coatings undoubtedly alter the surface environment of wood for microorganisms. Wood has also been shown to have a greater antimicrobial effect on common human-derived enteric bacteria than plastic or glass surfaces, indicating its potential to reduce the transmission and spread of pathogens on surfaces in the built environment versus synthetic materials. TallWood Design Institute and Sloan Foundation-funded UO research currently in preparation for publication, points to surface microbial community differences by material type with wood showing distinction from painted drywall, concrete and earthen plaster. That said, it is important that any positive impact on building microbiomes due to wood either be improved or at least not impaired by the addition of sealants and other protective coatings used on mass timber panels.

This research will investigate the impacts of mass timber coatings and humidity on the composition of mass timber surface microflora by performing metagenomic analysis on mass timber surfaces subjected to two different humidity regimes.  This will allow the study of microbes that would otherwise not be identified, providing better understanding of the composition of whole microbial communities which can be used to infer functional traits. In addition, this work will investigate the antimicrobial potential of a common commercially available sealant and alternative bio-based coatings being adapted for mass timber panels.  Mock microbial communities placed on the wood surfaces will be used to study the impacts of mass timber coatings on the survivability and transmissibility of viruses and bacteria of interest.