Exploring the integration of bio-based thermal insulations in compressed earth blocks walls

Abstract

The growing concern about the environmental impact of contemporary construction has posed emphasis on the possibilities offered by bio-based and raw earth construction. The front challenge for the establishment of earth-based technologies in contemporary building markets is the guarantee of high structural and energy performances, while maintaining a low environmental impact. This work focuses on the performance analysis of compressed earth blocks (from now on CEBs) which are currently commercialized for the construction of massive vertical envelopes, with high thermal inertia. However, to obtain an acceptable comfort and an optimized thermal behavior, CEBs walls must also reach a high thermal resistance. This issue can be overcame by the design of insulated CEB stratigraphies using bio-based thermal insulations presenting hygrothermal properties compatible with raw earth-based materials. In this way, the thermal performance of CEBs walls can be increased, while preserving their hygroscopic behavior. In this spirit, this work reports the results of the experimental characterization of three materials: CEB, lime hemp and sugarcane bagasse bio-based insulation panels. It includes their composition, their main physical (dry density, porosity, capillary water absorption), thermal (specific heat capacity, thermal conductivity) and hygrometric (sorption isotherm, water vapor permeability) properties. Finally, these experimental data are used for the implementation of several numerical simulations at a wall scale in a reference climate to estimate the hygrothermal performances of both uninsulated and bio-insulated CEB walls. The simulations allow for a better comprehension of CEBs’ behavior in view of their combination with the chosen bio-based thermal insulations, and give insights into possible moisture-related issues as mold growth or increase of U-value.