It is well known that bio-based materials may be susceptible to attack from a range of fungal organisms and therefore must be expected to be able to withstand or prevent such attack. One necessary condition for fungal colonisation is the level of water present – generally, in wood, for example, a minimum of 18-20% moisture content is required for fungal growth. Data for wood panels, for example, shows that at high relative humidity levels the moisture content (17%) is unlikely to be high enough for fungal growth. However, at the same relative humidity, the moisture content of a wood based fibre insulation is much higher (30-40%) and easily within the range at which fungal growth is likely. Despite this, there has been little work to determine whether the combination of materials with a structural element has an effect on potential fungal growth. For example, non-wood materials such as plant or animal fibre insulation may act as moisture reservoirs or buffers, which therefore, could increase or decrease the moisture content of adjacent wooden structural elements and thus affect their durability.

This paper details hygric and moisture based studies of some building materials and explores the development of an experimental approach to determine if there could be such an effect, using a modified form of existing wood decay testing methods. The results show that the type of insulation used can indeed have an effect on the durability of adjacent wood based materials.