Assessment of fungal development risk on bio-based thermal insulation

Integrating bio-resources into building materials appears as a key point in reducing the environmental impact of the construction industry. Hemp fibre, a locally sourced and annually renewable plant resource, is particularly well-suited for insulation applications. This article aims to determine whether the environmental conditions to which loose-fill thermal insulation in an attic is exposed promote fungal development. To investigate this, the insulation solution is applied in the attic of a demonstration house, and its in-situ behaviour is continuously monitored. Sensors are embedded within the insulation layer to measure temperature and relative humidity at various depths over an 18-month period, capturing the extreme conditions the material encounters. Such conditions are then considered to investigate, in laboratory, the risk of fungal development on hemp fibre. After inoculation and incubation, fungal growth is evaluated through visual analysis and colony-forming unit counts. An isopleth of the tested hemp fibre is then constructed, and the relationship between fungal development and available water is explored through the sorption curve. The results indicate that the risk of fungal growth is reduced under the conditions studied.