A review of multi-scale hygrothermal characteristics of plant-based building materials

The shift towards using materials derived from plants is considered an innovative approach to creating eco-friendly buildings and decreasing the energy expenses associated with the building sector. This study aims to provide a comprehensive analysis of these materials' hygrothermal properties to support their successful integration in both new construction and building renovation projects. It reviews the current state of research on the thermal and hydric properties of plant materials on various scales: raw aggregate/fiber, plant-based composite, wall, and building scale. The first part focuses on the physical, chemical, and hygrothermal characterizations of raw plant aggregates and fibers. The second part covers the main hygrothermal properties of plant-based composites (insulation boards and concretes) and compares their performance with conventional materials. The study then shifts its focus to the hygrothermal performance of walls integrated with plant-based materials in response to external climate conditions. Finally, a review of full-size buildings is conducted to investigate the impact of these materials on hygrothermal behavior at the building scale and to highlight their influence on the reduction of energy consumption. A lack of studies on plant-based materials was observed. There remain numerous areas that require further investigation at each scale. Consequently, the study includes discussion sections that provide guidance for future research to fill the gaps and advance the development of this type of material.