Development of a laboratory test method to assess the resistance of bio-based insulation materials against moulds

Abstract

Bio-based insulation materials have been increasing in the construction market in Europe. However, there is a lack of reliable standardised test method to determine their resistance against moulds. Moreover, existing test methods do not take into account real hygrothermal conditions in use. This research project aimed to develop a laboratory test method to assess the resistance of bio-based insulation materials against moulds. The test method was applied to different bio-based insulation materials: wood fibre, loose fill cellulose, straw and hemp-flax. The materials were artificially contaminated with moulds. Based on a hygrothermal study on use classes, two different climatic conditions were tested: 26°C 95 % of relative humidity and 26°C 85 % of relative humidity. After four weeks of mould exposure, both a visual examination and a counting of cultivable fungal units were performed. It was clearly demonstrated that the quantitative analysis of mould growth was necessary to assess the resistance of bio-based insulation materials against moulds. Results from two different laboratories gave evidence that this test method was reliable whatever the tested bio-based material. It was shown that among 8 tested materials, 2 were resistant to moulds at 95% of relative humidity. In addition, 2 untreated bio-based insulation materials which were not resistant to moulds at 95 % of relative humidity were resistant to moulds at 85% of relative humidity, thus enhancing the suitability of bio-based materials for insulation. A proposal of a mould test taking into account realistic hygrothermal conditions was discussed.