2026

Lappalainen, V.; Sorvari, J.; Sohlberg, Elina; Pasanen, P.

<p>Moisture damage in buildings is a significant source of indoor air problems, releasing e.g. volatile organic compounds (VOCs) and microbially produced VOCs (MVOCs), which can cause unpleasant odors and health symptoms. However, interpreting MVOCs as indicators of mold is challenging due to their various sources and limitations in analytical methods. The objective of this study was to identify the most critical factors influencing VOC emissions from moisture-damaged wall structures into the indoor environment via structural air leakages. The research was conducted using the VTT Indoor Air Quality (IAQ) Simulator and analyzed with Principal Component Analysis (PCA). The IAQ simulator was used to investigate the transport of airborne impurities from mold-contaminated wall structures in realistic building conditions and the systematic manipulation of key environmental parameters. The resulting dataset was subjected to multivariate analysis to identify the most influential factors contributing to IAQ degradation in moisture-damaged structures. The key conclusions revealed that material relative humidity was the most significant single factor affecting all VOC concentrations; higher humidity consistently increased emissions. Four specific ketones (2-pentanone, 2-hexanone, 2-heptanone, and 2-octanone) were clearly identified as originating from microbial growth, with their concentrations being significantly higher in the presence of active mold growth. Pressure differentials had only a borderline effect on gypsum board emissions, while the insulation layer showed no significant impact on any of the identified VOC components. These findings underscore the critical role of relative humidity in determining indoor VOC profiles and highlight the value of multivariate methods in assessing mold-related indoor air problems.</p>