Comparison of the hygric behaviour of three hemp concretes

• This study compares the hygric behaviour of three hemp concretes.
• The materials differ from their formulations and manufacturing methods.
• Sorption curve, water vapour permeability and moisture buffer value are measured.
• Hygric diffusivity is calculated from sorption and water vapour permeability.
• The results show slight differences between the three materials.

Hemp concrete is a bio-based building material the main qualities of which are its low environmental impact and its hygrothermal behaviour. Even for one kind of application (for example: wall), several compositions and manufacturing methods are encountered in the market. This study compares the hygroscopic behaviour of three hemp concretes used for building walls to identify whether composition and manufacturing have an impact on hygric properties. The investigations are based on the measurement of the sorption curve, of the water vapour permeability versus humidity and of the moisture buffer value. Moisture diffusivity is calculated from the sorption curve and from the water vapour permeability. The results underline the high transfer and storage capacities of these materials; they are classified as excellent (or nearly excellent) hygric regulators. A slight effect of porosity, connected with composition and manufacturing method, is observed.