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 that is lightweight, or ultra-lightweight even. Its thermal mass and vapor 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 buildings, 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.
Hempcrete is an Insulating lining
Hempcrete insulating lining is a combination of Tradical®PF 70 or Tradical® Thermo formulated air lime and. It meets the eco-efficiency objectives that are now applied to renovation projects, from renovating houses to restoring of historic buildings.
A hempcrete insulating layer that is cast directly on the substrate without any joints or air space guarantees continuity between materials, avoiding thermal bridges in particular, which are often present when conventional insulation materials are used. It not only improves the existing characteristics of the walls on which it has been cast, but also brings its own set of properties that are unrivalled on the renovation market:
Dynamic absorption of temperature variations Dynamic absorption of relative indoor moisture variations
Eliminates the ‘cold wall effect’ The end result is excellent insulation, a pleasant living atmosphere, and healthy indoor air regardless of season or weather
Landmark materials for long-lasting insulation This bio-based insulation layer contributes to the durability of the renovation and the building as a whole thanks to:
its moisture-regulating properties,its dimensional stability – no sagging – and the insulating properties stay the same throughout. In addition, hempcrete insulation stays free from bacterial attacks, insects such as termites, fungi (thanks to the high pH of air lime) and rodents!
Tradical® hempcrete has been tested for its service life. It can resist 20 freeze/thaw cycles, which is comparable to the service life of limestone.
By installing this type of insulating lining, buildings can withstand the vagaries of time and you can make significant savings on future maintenance or renovation costs. And it is worth noting that all performance ratings stay the same for the whole service life of the hemp-lime composite (Ref.: MAP 04B1 05 01, LCA for a 100-year period).
III. A flexible solution
The flexibility offered by Tradical hempcrete insulating lining provides efficiency and savings in many areas. The thickness of the cast material varies from 5 to 20 cm depending on energy-saving objectives, the building’s orientation and surroundings, etc. Builders have a choice of several casting methods:
manually using the traditional trowelling method for small thicknesses, manually, by pouring the hempcrete in between the wall and shuttering, mechanically, by spraying the hempcrete in between the wall and shuttering or directly onto the wall.
Disclaimer: This article is originally published on https://www.bcb-tradical.com/en/hempcrete/what-is-hempcrete/