Hempcrete is an environmentally friendly building material made from hemp, a plant that is a strain of the Cannabis sativa plant species. Hempcrete uses the shiv (the woody core of the Cannabis plant) along with a lime binder and water to make a biocomposite mixture.
Applications of Hempcrete
Hempcrete can be used to build walls and in-fills in new build properties with timber structures. It can also be used as floor and roof insulation. It is possible to mould the hempcrete into any shape before curing, meaning that it is a very versatile material for use in insulation of old and historic buildings and masonry walls.
Advantages of Hempcrete
There are many advantages to using hempcrete as a building material, including environmental, financial and health benefits.
Hempcrete is an excellent insulator. As such, the demand on heating systems and air conditioning systems is reduced, resulting in a lower impact on the environment and saving homeowners money on energy bills.
Hempcrete is also resistant to damp, mould, and pests. Damp poses serious risks to people’s health, in particular respiratory health, and is a problem that affects a huge number of older buildings constructed with traditional materials.
The lime binder used in the hemp mixture helps to make the material rot and pest resistant and does not need additional chemical treatments to achieve good resistance levels. This reduces the amount of toxins in the home, improving air quality and reducing risk to people’s health.
Hempcrete, along with the lime or clay plaster used to coat the hemp building blocks, is able to regulate humidity through its hygroscopic properties, meaning it is able to effectively absorb moisture from the air. When humidity levels drop, hempcrete is able to release moisture back into the air.
Condensation can be reduced as a result of these hygroscopic properties, and the occurrence of damp spores can be greatly reduced, increasing the health benefits of this natural building material.
While the hemp plant is being grown, it naturally absorbs carbon dioxide from the atmosphere, which poses clear environmental benefits. An additional benefit of hempcrete is that it continues to absorb carbon dioxide after it has been made into walls or other building materials. Some have claimed that hemp and lime biocomposites can absorb around 110 kg of carbon dioxide per cubic meter of wall.
Those living in houses with hempcrete walls or insulation can save substantial amounts on energy bills due to the superior heat absorption and retention capacity of the natural building material, thus also reducing the impact heating and cooling systems have on the environment.
Disadvantages of Hempcrete
Hempcrete is not suitable for constructing load-bearing walls, and only timber frame structures have been validated as suitable in hempcrete construction. However, it is useful for renovating old buildings to comply with modern energy efficiency standards, and is widely used as an in-fill.
Hempcrete walls are also often thicker than walls built with traditional materials, meaning floorspace inside a building can be reduced.
Hempcrete also takes a long time to cure, sometimes taking a few weeks. The curing process can also be delayed by wet weather, posing a significant disadvantage to concrete that only needs a few hours to fully cure.
A huge disadvantage of hempcrete is not to do with the properties of the material itself, but more the legislation around it. It is still illegal in many countries to grow hemp, and as such anyone wanting to produce and build with hempcrete would have to import the hemp from elsewhere. This adds to the material’s environmental impact, and increases the financial burden on the buyer.
As hempcrete has not been widely taken up as a standard building material, hempcrete products are not subject to standardization. This means that hempcrete is only safe for non-structural purposes.
Currently, hempcrete is more expensive than other, less environmentally friendly building materials, and as such uptake of the alternative material has been limited. While it has excellent environmental benefits and offers a huge range of advantages over concrete, from resistance to pests, mould, damp, and even fire, it currently has a limited range of applications as it cannot be used for load-bearing structures. With more research, hempcrete has great potential as a viable and environmentally friendly building material suitable both for new builds and renovations in old and historic buildings.
Sources and Further Reading