Durability and hygrothermal performance of bio-based materials in Northern European climate
Bio-based building materials (3BMs) are one of the solutions for how the construction industry can mitigate its negative environmental impact because of energy consumed in material production and due to the insufficient thermal insulation of buildings, as, in general, these materials sequester CO2 in them and have low thermal conductivity. One of the obstacles that these materials must overcome in order to become more widely accepted is the general belief that they are inferior to traditional building materials in terms of durability – mostly biodegradation. The objective of this study is to assess biodegradation of 3BMs in real operating conditions. In order to achieve it, this article analyses the in-situ hygrothermal performance of 3BMs in the Northern European climate, situated in various parts of the structure, to measure their operating conditions with relative humidity sensors when subjected to humid continental climate conditions. The results are then used to simulate the humidity conditions in the laboratory for the biodegradation tests. Several hemp-based materials are tested as well as traditional construction materials for reference. The materials are inoculated with a mixture of six different fungi that are typical to 3BMs and kept in the set laboratory conditions. After a period of 45 days and 4 months the pH values of materials are tested, fungal growth is evaluated, and genus determined according to macromorphological and micromorphological characteristics. Preliminary results indicate that 75% RH is a safe level for 3BMs with mineral binder, but when exposed to 99% RH for longer periods fungal growth is observed, but only when reduced binder content is used and pH level drops below pH 9.30. The overall results indicate that 3BMs are usable in Northern European climate conditions.