Thermal and mechanical behavior of straw-based construction: A review

Bio-based materials such as straw are becoming a promising alternative to improve the building energy performance
and to reduce its carbon footprint. When compared to common building construction materials, biobased
materials control the temperature and the relative humidity variation to ameliorate the indoor comfort
with a low embodied energy and CO2 emission. This paper presents a comprehensive review of the thermal and
mechanical properties of straw-based materials and buildings. The objective is to synthesis the work that has
been carried out by the research community and to compare the results. The paper first introduces straw bale as a
construction material from a historical viewpoint and in the context of the current building sector. The second
part focuses on the available chemical and microstructural data of the straw fiber. The third part refers to the
thermophysical and mechanical properties of the bales. The fourth part reviews the numerical and experimental
studies done at the wall scale. The fifth part describes straw bale construction methods considering the regulation,
structure requirements, and life cycle assessment data. Last, a critical analysis of the currently available
data on straw as a building material is carried out and pending research issues are discussed. It was found that,
despite abundant literature on structural and thermal properties of straw bale constructions, there is still a lack of
some information. At a fiber scale, more research should be done to compare straw fibers to other natural and
synthetic fibers. At a bale scale, further pH-related research is needed because it affects the material’s interior
conditions and durability. In addition, a thermal conductivity model for straw should be developed. On a bigger
scale, the hygrothermal characteristics of various types of walls must be measured and computed experimentally
and theoretically under various exterior and internal situations. More research is needed to improve the sound
resistance of the straw wall by adding new layers capable of absorbing acoustic waves. Studies on the energy
behavior, cost analysis, and how interior air moisture is self-regulated in straw buildings are needed at the
building size. Therefore, a lack of consistent data among the different studies was noted depending on the straw
characteristics.