1% Better - Hempcrete
With this month’s 1% Better topic focusing on concrete solutions and possible eco-friendly alternatives today’s blog takes an in depth look at Hempcrete. SOLID Engineer Sebastian has done extensive research on Hempcrete as an alternative building material, even basing his thesis on the topic and today shares his knowledge with us.
In our last ‘Concrete Solutions’ blog we learned that whilst concrete is a strong, reliable building material, its production accounts for 7% of global carbon emissions so it is important to be considering alternatives. Plant-based biomaterials, such as hempcrete, are looking promising. They offer sustainable solutions to the built environment industry and aid in achieving sustainability goals.
What is Hempcrete?
Hempcrete can be defined as a breathable hygroscopic non-load bearing material which is comprised of hemp hurds, a binder and water. Hempcrete has a low-medium density, excellent thermal properties, a total negative CO2 emission, good hygric properties, high acoustic absorption, and a resistance to fire. The above-mentioned characteristics lead to an improved energy rating and total indoor performance of a building.
Hempcrete is formed by mixing water with a combination of hemp hurd and binder in various proportions. The mix design of hempcrete will differ according to the required application. Less binder is used to achieve a lower mechanical property (roof insulation), a moderate amount of binder is used to achieve good mechanical properties (wall application) and the highest amount of binder is used to achieve high mechanical properties (floor application). Hempcrete can be produced in three different methods. It can be produced by spraying, prefabrication and moulding. Each method has its pros and cons with moulding having a long drying time, spraying being expensive and prefabrication being the fastest, but requires large production facilities.
Sustainability of Hempcrete
The materials used in the built environment industry tend to have a high encapsulated energy. The production of these materials often has multiple production stages and thus result in high encapsulated energy. With an increase in encapsulated energy, it can be expected that an increase in emissions occurs.
Hempcrete is a hygroscopic material and is characterized by its ability to readily attract and hold water molecules from their surroundings, either by absorption or adsorption. This material property will aid in the humidity control of the surrounding environment. If there’s an increase in the room temperature, the relative humidity will decrease which allows the material to absorb moisture from the air. The opposite occurs when the temperature decreases, and the hygroscopic material will desorb moisture which will increase the surrounding relative humidity. This process allows hempcrete to improve the indoor air quality and human comfort of a building. This gives hempcrete its ability to be an excellent thermal insulator.
Since hempcrete is comprised of hemp hurd, a plant-based biomaterial, hempcrete enables the industry to harness the beneficial natural properties developed over time in nature to achieve specific performance characteristics. A plant-based biomaterial will store and capture atmospheric CO2 by means of photosynthesis. As opposed to the conventional construction materials which require multiple production phases to achieve specific properties, plant-based biomaterials naturally provide these properties without undergoing multiple production phases. This reduction in phase production ensures that a plant-based biomaterial has a low encapsulated energy. This give hempcrete its ability to achieve a total negative CO2 emission over its life-cycle.
Hemp, the critical ingredient of hempcrete, is a grown from the cannabis sativa plant which is cultivated globally. The cultivation of hemp has excellent economic value for farmers with an ease of growing, a crop yield of approximately 21 ton per hectare per year and a consistent, sustainable supply of raw construction material for the built environment industry as well as other industries. The plant is good for crop rotation since it grows extremely fast and it does not require any pesticides or chemical fertilizers.
Hempcrete’s low environmental impact and high hygroscopic properties will positively impact the built environment industry as an alternative sustainable construction material to that of conventional concreted based construction materials. Why not consider it for your next project?
If you are researching concrete alternatives or have tried plant-based biomaterial for yourself we would love to hear from you. Do contact the SOLID team to discuss your findings. We would love to share them as part of our 1% Better Every Day mission.