Phase 1
In Phase 1 of our project we have turned 2 old barns into luxurious and unique accommodation. We have chosen to leave the hemp blocks without plaster, because the rustic look is sympathetic to the building’s original purpose. We also like the idea of being able to look at a living wall, knowing that the blocks are doing their work. No matter what the weather outside, inside both houses are warm in the winter, cool in the summer, very dry and very quiet. We are pleased with both the aesthetic and functional aspects of using hemp blocks and will definitely be using them in the remainder of the houses we intend to restore in our epic project. It is expected that the initial cost of the material will be recouped through reduced energy costs for heating and cooling.
So what is hemp?
Hemp is a versatile and sustainable crop. It has gained attention for its potential environmental benefits and its use in various industries. From textiles to biofuels, hemp offers a range of advantages, particularly in its potential to reduce environmental impact and provide eco-friendly alternatives to conventional materials.
Growing hemp presents numerous environmental benefits. As a fast-growing plant, hemp can reach maturity in as little as 90-120 days, making it a highly renewable resource. Additionally, hemp requires minimal pesticides and herbicides, and it naturally inhibits weed growth, reducing the need for harmful chemicals. Its deep roots also help prevent soil erosion and improve soil health, making it an excellent rotational crop. Through a process known as carbon sequestration, hemp plants absorb carbon during photosynthesis and store it in their biomass and in the soil. This can contribute to mitigating the effects of climate change by reducing the amount of carbon dioxide in the atmosphere. According to a European Commission report the carbon sequestering properties of hemp are remarkable. In just five months one hectare (2.5 acres) of hemp can trap between 9 and 15 tonnes of carbon dioxide.
One innovative use of hemp in construction is in the form of hempcrete, a sustainable building material made from the inner woody core of the hemp plant, known as the hurd, mixed with lime and water. Hempcrete offers several advantages over traditional building materials such as concrete:
- Sustainability: Hempcrete is a renewable and low-impact material, as hemp plants absorb CO2 during growth and the production of hempcrete itself has a lower carbon footprint compared to traditional concrete.
- Insulation: Hempcrete provides natural thermal insulation, helping to regulate temperature and reduce the need for heating and cooling, which can lead to energy savings and reduced greenhouse gas emissions.
- Moisture regulation: Hempcrete is breathable and can manage moisture effectively, reducing the risk of mould and improving indoor air quality.Creating a significantly healthier environment free of toxins, unwanted bacteria, viruses, pests and moulds.
- Durability: While not as strong as concrete, hempcrete is a durable material that can last for many years, providing long-term benefits for building structures.
- Versatility: Hempcrete can be used for a variety of construction applications, including wall insulation, roofing, and flooring, offering flexibility in design and construction.
By utilising hempcrete in buildings, the construction industry has the potential to reduce its environmental impact and contribute to sustainable building practices. Additionally, the use of hemp-based materials can support the development of a more circular economy, in which resources are used efficiently and waste is minimised.
In conclusion, the cultivation of hemp and the use of hemp-based materials such as hempcrete offer significant environmental benefits. By promoting sustainable farming practices, reducing carbon emissions, and providing eco-friendly alternatives for construction, hemp has the potential to play a valuable role in addressing environmental challenges and promoting a more sustainable future.
We are using hemp blocks from a Portuguese Company, Cânhamor, based in Alentejo. Their idea was to take advantage of Portugal’s relaxation of laws governing the cultivation of hemp, part of the cannabis family of plants. With official permits, the cultivation of medicinal cannabis and hemp in Portugal has been permitted since 2018. The laws have been refined since then, but with authorisation from the General Directorate of Food and Veterinary Affairs, farmers can grow hemp as long as there is oversight from regulators. It marks a revival for hemp in Portugal. It was an essential raw material for the nation’s maritime expansion, which began in the 15th Century, when it was used to make cords, ropes and sails. Hemp fibre was prized for its durability, a quality which has caught the attention of today’s construction industry.
The blocks are made of hempcrete, a mix of hemp plant parts, water and limestone powder. The blocks have several advantages over traditional building materials. As well as being much less carbon intensive to make, hemp blocks are better at insulating from heat and sound than brick and concrete. They are also very resistant to fire. In 2019 researchers in Australia conducted tests on hemp walls including simulating a bush fire, and found the material very resistant to fire damage.
However, hemp blocks have to compete with concrete which is currently cheaper, stronger and well known to builders. Currently Cânhamor produces between 4,000 and 10,000 blocks every month, enough to build about three houses. Demand is steadily increasing and the company is building a 2nd factory, which should produce about 120,000 blocks a month.
At the moment Cânhamor buys hemp shiv from abroad which pushes up the cost of its blocks. They plan to persuade more local farmers to cultivate the plant. “There was no factory because there was no cultivation, and there was no cultivation because there was no factory. We have the opportunity and the privilege to break this cycle,” Mr Kaspin says. To produce enough hemp fibre in Portugal for the number of blocks in demand, he estimates that 1,000 hectares of hemp will need to be cultivated and he is in talks with several farmers, willing to try hemp cultivation. “With local materials, and with larger capacity, production costs will drop significantly. In 2024 we will be able to offer our blocks at much lower prices,” he predicts. “Even cheaper than concrete.”
In the production of Cânhamor hemp blocks, they are very close to achieving 100% Zero Waste. No chemical additives are added to the mixture and as there are no heating processes, there are no harmful gas emissions in their production. The benefits of using hempcrete are multiple and far reaching.
