The innovation of hempcrete as a building material lies in its function as a multi-performance material. It can completely replace mineral aggregates in conventional concretes, and historically it was added to concretes and mortars to prevent shrinkage in gypsum or clay brick [3]. When cured it retains a large amount of air, with a density equivalent to 15% of traditional concrete, making it an excellent thermal and acoustic insulator. An interesting feature of the material is that it is a good thermal insulator and has a high thermal inertia [4]. That is, although light and porous, hemp can store energy quickly and release it gradually, making it effective for climates with high temperature variations between day and night. It also has good fire resistance, is non-toxic and is naturally resistant to mould and insects. There are even surveys that suggest that the hempcrete is a carbon negative material, which in addition to offsetting the carbon emitted in production, actually stores additional carbon within the material itself.
The use of hemp in civil construction is not new either. Hemp concrete was discovered in the pillars of bridges built by the Merovingians in the 6th century in what is now France. The Romans are also known to have used hemp fibre to reinforce mortar in their buildings.
In the latter case, the material can be used as a thermo-acoustic insulator, much like glass wool or rock, or as hemp concrete, often called hempcrete. To create it, hemp, powdered limestone and water must be mixed to obtain a thick paste. Through chemical reactions between the components, the mixture petrifies and becomes a light, but quite resistant block.
