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International audience; In the context of global warming associated with the excess of energy consumption, energy saving and environmental sustainability in buildings have become significant issues at both national and European levels. Therefore, the adoption of energy-efficiency measures in new and renovated dwellings will increase the demand for thermal insulation, which is crucial to improve the housing comfort by reducing the heat loss through the building envelope. Over the past two decades, several bio-based materials have been used in building thermal insulation, such as hemp concrete. Promoting the use of hemp concrete in new constructions and restoration of existing buildings first requires a validation of its hygrothermal behavior at both wall and building scales. For this, several models dealing with various physical aspects of hemp concrete were developed to understand their impact on the prediction of changes in temperature and relative humidity. These physical phenomena include hemp concrete hygroscopic hysteresis and thermal dependency of sorption curves. The preliminary results show that hysteresis has a significant influence on the numerical prediction in the short-term, while temperature dependency has less influence at the wall scale. The next part of this article is devoted to the study of these phenomena at the room scale by monitoring the internal conditions and energy consumption of a virtual hemp concrete office. The results highlight the fact that hysteresis and thermal dependency have low impact on indoor conditions, which could probably be related to the other parameters at the room scale.

Lime—Hemp (LH) composites are innovative building materials. They can be used in renovated or thermally upgraded as well as new buildings. This article reviews hygrothermal properties of LH wall assemblies and compares their transient performance to five traditional assemblies using WUFI ® simulation. While the annual quantity of energy was similar, LH assemblies showed a strong ability to improve indoor comfort.