Afrimat Hemp is a Cape Town-based company, launched in 2021, which is pioneering and beneficiating the industrial hemp value chain in Africa. Afrimat Hemp has the expertise to bulk process the hemp plant and use it in natural, carbon-absorbing construction materials, breathable lime-based plasters and mortars.

What is hempcrete and what does it consist of?

Hempcrete (also known as hemplime) is a bio-composite material, a mixture of hemp, lime and sand, which is used as a material for construction and insulation. The physical properties of hempcrete include its relatively low thermal conductivity, medium-low density, very high specific heat, strong thermal insulation, and thermal mass, ensuring building comfort and preventing sudden heat changes. The woody core hemp plant is processed with a locally formulated lime binder from Afrimat, and water is added to form Afrimat Hempcrete.

Why construction with hemp/hempcrete?

Hemp grows quickly and requires minimal water and pesticides, making it an ideal crop for sustainable farming and a viable crop given the water scarcity in South Africa. The plant absorbs large amounts of carbon dioxide during growth, and the woody core, which is typically discarded, is used to make hempcrete. This means that hempcrete is a carbon-negative building material, which actively reduces carbon in the atmosphere. Hemp blocks ensure humidity regulation, acoustic insulation, protection and fire resistance. It’s ten times stronger than concrete and one-sixth of the weight.

What are the other benefits of constructing with hempcrete?

• Hempcrete is a highly energy-efficient material: it has excellent insulation properties, which means buildings constructed with hempcrete require less energy for heating and cooling, reducing energy consumption and carbon emissions
• Hempcrete is a circular material, meaning it can be reused or recycled at the end of its lifespan; unlike traditional concrete, which is difficult to recycle and often ends up in landfills, hempcrete can be crushed and used as a soil conditioner, returning valuable nutrients to the earth
• Manufacturing (and constructing with) hempcrete is beneficial for local economies as hemp farming and construction with hempcrete provides much-needed employment opportunities for rural communities
• It reduces the dependency on fossil fuels
• It supports sustainable and resilient local economies.

Could hemp building materials replace traditional building materials?

No. Afrimat’s ‘hempcrete’ product is not intended to replace traditional materials such as steel and cement in constructing a building’s substructure and frame. Rather, hemp is used as the infill material that provides insulation.

Is constructing with hemp more expensive than traditional building materials, and if so, which efficiency benefits are there to justify cost?

Although hempcrete is currently slightly more expensive than conventional building materials, it is becoming more price competitive as local supply and manufacturing ramps up.

Efficiency benefits:

▪ Hemp blocks are more effective at insulating buildings, and because they are vapour-permeable, they act as natural humidity regulators, thus preventing mould

▪ Further, this building material, which has long been used in construction and other applications in markets such as France and Europe, is also a fire retardant

▪ Using hemp as the infill material in high-rise buildings also significantly reduces their weight, which means less steel and concrete is needed in the substructure

▪ Hempcrete helps to lower carbon emissions. European studies show that every cubic metre of hempcrete sequesters 75kg of carbon dioxide. Industrial hemp also has a super fast-growing cycle versus forests, which can take years to take root. According to a Cambridge University researcher, a hectare of hemp can absorb between eight and 15 tons of CO₂. In comparison, forests capture two to six tons only, depending on the type of trees, region, etc.