Known internationally as Hempcrete. Carbon-negative building material obtained by mixing the woody part of the hemp stem (shiv) with lime-based binders. Creates a monolithic, thermally insulating envelope that actively regulates indoor humidity.
The silica naturally present in hemp shiv triggers a pozzolanic reaction with lime, petrifying the plant fibre and making it immune to rot, fire and insects.
Hemp-lime biocomposite is the paradigm of regenerative architecture. It not only avoids polluting during production, but actively removes carbon dioxide from the atmosphere, storing it for centuries inside the walls of buildings.
The material is obtained by mixing hemp shiv (the fragmented woody core of the Cannabis sativa plant) with water and a lime-based binder. Hemp shiv is naturally rich in amorphous silica, which reacts chemically with the lime (pozzolanic reaction), petrifying the plant fibre. The result is a mineral sponge impervious to fungi, insects or rodents.
Unlike ordinary concrete, hemp biocomposite is not load-bearing (compressive strength ~ 1 MPa). Its real strength lies in dynamic hygrometry: the high porosity stores excess moisture (avoiding condensation) and releases it when the air becomes too dry, acting as a passive conditioner.
European and international references applicable.
Cast-in-place hemp biocomposite requires long drying times before finishes can be applied (lime or clay renders). In cold or damp climates, pre-dried factory blocks (prefabricated hemp blocks) are preferred to avoid construction delays.
Mix cast or machine-sprayed into formwork around structural timber frames.
PRC.15 · Open the processInsulating masonry built with pre-dried blocks laid with thin-joint lime mortar.
PRC.15 · Open the processVery low density mixes (200 kg/m3) laid dry or wet on slabs for thermal insulation and summer inertia.
PRC.31 · Open the processThick bio-renders for thermal bridge correction in heritage or high-quality renovations.
PRC.42 · Open the processNegative values indicate the material removes greenhouse gases from the environment (Carbon Sink). Building a detached house infill walls with hemp biocomposite compensates for the CO2 emitted casting the reinforced concrete foundations.
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