What is hempcrete?
Hempcrete is a composite made of natural materials, lime and hemp. The lime component consists of air lime that is formulated to speed up the setting process. The hurds are made using hemp stalks. Hemp is a plant that can be grown without using plant protection chemicals, requires little water and contributes to agricultural soil regeneration. The combination of lime and hemp creates a natural concrete which is lightweight, or ultra-lightweight even. Its thermal mass and vapour permeability properties result in high-performance buildings capable of meeting current and future thermal regulations.
Hempcrete is one of those bio-based materials that can be used to build, renovate and restore all types of building, from houses and apartment blocks to service and public sector buildings and all types of built heritage, from traditional buildings to listed historic buildings.
Hempcrete is made by mixing lime and hemp in proportions adapted to the work to be done. This makes it very versatile, and it can be used to build insulating walls, linings, roofs, screeds, attic spaces and renders.
What are the benefits of hempcrete?
Areas of use. It can be used to build self-insulating walls, roofs and screeds It can be adapted to all types of building project including new builds and renovations.
It is not a load-bearing material. Consequently, when building walls, it is cast around a primary or secondary structural frame made of timber, metal or concrete. It is also used to replace deteriorated cob in half-timbered walls. As an insulating lining, it can be cast on all standard mineral substrates.
Casting methods. Initially hempcrete was cast manually. Later, specific mechanical projection solutions arrived on the market, making processes much more efficient. A concrete mixing station combined with a concrete mixing truck and a conveyor belt is also an excellent solution frequently used by professionals to cast insulating roofs and screeds. Nowadays, workshop-prefabricated walls can also be produced for a faster build, without losing any of the benefits of a material that provides excellent thermal and moisture control performances.
Thermal performance. The first feedback for newly built houses with hempcrete showed that bioclimatic houses can be built with drastically reduced heating costs and no air conditioning. On average, the estimated cost of heating for this type of house is around €1-2 per m². But it can also be even lower, as proven by the €35 a year bill paid by the owners of a house built by the architect JM Naumovic in Vendée.