Fungal growth on a hemp-flax-cotton biobased insulation materials and their potential to emit microbial volatile organic compounds (mVOCs)

Bio-based insulation materials contribute to building decarbonization and good hygrothermal performance. However, in humid conditions, they can promote fungal growth and the emission of mVOCs, affecting indoor air quality. The aim of this study is to assess the influence of aging on the susceptibility of bio-based materials to promote fungal growth and VOC emissions, and to investigate potential mVOC emissions. To this end, a hemp-flax-cotton insulation material was subjected to a 3-month accelerated aging process under alternating humidity cycles. The material was exposed to weekly dry (11± 4%) and humid (60± 2%) conditions at 25± 0.8°C. Native and aged materials were inoculated by fungal spores using dry aerosolization system and incubated at 95 ± 1% for 30 days. Fungal development was quantified using the cultured cell method. VOCs and SVOCs were characterized for both native and aged materials, whereas mVOC emissions were monitored from inoculated native materials on days 1, 7, 9, 15 and 30. All compounds were identified and quantified using TD-GC-MS/FID and HPLC. Results showed strong fungal proliferation on both native and aged materials, with spore concentration reaching 100–1000 times the initial inoculum. The material was identified as very low VOC emitter in its native state. Aging did not significantly modify the overall VOC emission profile. During 30 days of incubation, emissions of 74 VOCs decreased, whereas 10 newly detected compounds (1–13 µg m −2 h −1 ) appeared between days 7 and 9, peaked on day 9, and then progressively declined, suggesting fungal metabolic degradation of the material.