Moisture-resilient Bio-based Walls: Innovation or Illusion?

Bio-based materials show a promising potential for the CO2 transition in the current construction industry from a linear to a circular economy. They are renewable, locally available, fast-growing, valorise rest streams of well-established industries and sequester CO2 resulting in low embodied energy. Despite an increasing use as sustainable building methods, their exact hygrothermal response in vapour-open walls is still under research. Degradation, upscaling, material variability, legislation, lack of standards, poor perception and absence in confidence lead too often to applications primarily limited to low-rise buildings and committed (self-)builders. The purpose of this research is to integrate bio-based materials in futureproof vapour-open wall construction systems. There will be focused on different building methods, e.g. monolithic walls, masonry walls with interior retrofit and classic wood framing. Thus, the research is applicable to both new and renovated buildings. The research will be done by a laboratory characterisation and in situ monitoring campaign representative for the Flemish building context, complemented by simulations. The hygrothermal analyses will be carried out for existing and new robust wall systems suitable for wider application and upscaling. Heat, Air and Moisture (HAM) simulations will be carried out to study the hygrothermal behaviour of the wall systems, investigate variants and define key parameters. The experimental work will function both as input and validation for the simulations, because bio-based materials are scarcely represented in simulation databases. The most promising wall systems will then be built and investigated by lab testing. The research methodology aims to be reproducible for future-emerging bio-based materials and lower the threshold for bio-based building systems.