Volatile organic compound (VOC) emissions from indoor sources are large determinants of the indoor air quality (IAQ) and occupant health. Cross-laminated timber (CLT) is a panelized engineered wood product often left exposed as an interior surface finish. As a certified structural building product, CLT is currently exempt from meeting VOC emission limits for composite wood products and confirming emissions through California Department of Public Health (CDPH) Standard Method testing. In this study, small chamber testing was conducted to evaluate VOC emissions from three laboratory-produced CLT samples: One bonded with a new soy-based cold-set adhesive; a second bonded with a commercially available polyurethane (PUR) adhesive; and the third assembled without adhesive using dowels. A fourth commercially-produced eight-month-old sample bonded with melamine formaldehyde (MF) adhesive was also tested. All four samples were produced with Douglas-fir. The test results for the three laboratory-produced samples demonstrated VOC emissions compliance with the reference standard. The commercially-produced and aged CLT sample bonded with MF adhesive did not meet the acceptance criterion for formaldehyde of ≤9.0 µg/m³. The estimated indoor air concentration of formaldehyde in an office with the MF sample was 54.4 µg/m³; the results for the soy, PUR, and dowel samples were all at or below 2.5 µg/m³.

A broad range of building performance monitoring, sampling, and evaluation was conducted periodically after construction and spanning more than a year, for an occupied office building constructed using mass timber elements such as cross-laminated timber (CLT) floor and roof panels, as well as glue-laminated timber (GLT) beams and columns. This case study contributes research on monitoring indoor environmental quality in buildings, describing one of the few studies of an occupied mass timber building, and analyzing data in three areas that impact occupant experience: indoor air quality, bacterial community composition, and floor vibration. As a whole, the building was found to perform well. Volatile organic compounds (VOCs), including formaldehyde, were analyzed using multiple methods. Formaldehyde was found to be present in the building, though levels were below most recommended exposure limits. The source of formaldehyde was not able to be identified in this study. The richness of the bacterial community was affected by the height of sampling with respect to the floor, and richness and composition was affected by the location within the building. Floor vibration was observed to be below recognized human comfort thresholds.

Wood is often used as an interior surface finish in buildings, including exposed cross-laminated timber panels and other structural mass timber members. Building occupants generally have a positive reaction to visible wood elements used in building interiors due to the visual qualities associated with wood being a natural material. This study aims to identify any thermal comfort impacts of wood interior environments using subjective occupant-reported perceived thermal sensation during two experiments conducted in a climate chamber fitted with either white-painted gypsum wallboard or unfinished laminated Douglas Fir wall panels. In the first experiment, the thermal environment was continually varied while the visual stimulus of the wall type remained constant. Irrespective of wood or white wall treatment type, thermal history played a significant role in the perceived thermal comfort of participants under continually modulating temperatures. In the second experiment, a slightly warm steady-state thermal environment was maintained while one of the two wall treatments was revealed from behind a black curtain. While the shift in thermal sensation toward neutral was greater with wood walls than with white walls, the difference was not found to be statistically significant and appears to diminish after 15 min of exposure to the new visual surroundings.