The Potential for Hempcrete
At Biofibre Build, our core mission is to revolutionize the construction industry by providing better, faster, and more affordable, and importantly, carbon-efficient building materials engineered from biofibers. Founded in September 2023 and based in Greenville, South Carolina, we are a pioneering biomaterials company committed to transforming sustainable industries by growing and processing natural fibers such as hemp and bamboo. In line with our vision to help builders create better homes faster for less cost using premium, planet-friendly products, we are excited to delve deeper into hempcrete, a key hemp building material with significant potential for eco-friendly construction and sustainable building.
What is Hempcrete?
Hempcrete, also known as hemplime, is a biocomposite material used for construction and insulation. It's a mixture primarily composed of the inner woody core of the hemp plant (hemp shives or hurds), a lime-based binder, and water. The binder typically consists of hydrated lime or natural hydraulic lime. Sometimes, sand or pozzolans are added to the mixture. A small amount of cement and/or pozzolanic binder may also be included to speed up the setting time. The resulting mixture develops into a solid, light, and durable product.
Applications of Hempcrete
Hempcrete has been utilized in construction since the early 1990s, particularly in France and more recently in Canada. Its primary applications include the construction of non-weight bearing insulating infill walls, as it lacks the compressive strength for foundations and load-bearing elements. It is supported by a structural frame. Hempcrete is also suitable for renovating old buildings made of stone or lime. It can be used for various purposes in buildings, such as roof, wall, slab, and render insulation, each with specific formulations.
Three main construction techniques are currently employed: casting, spraying hempcrete directly in place on the construction site using forms, and stacking prefabricated blocks delivered to the site. Once implemented between timber framing, drywall or plaster is often added for aesthetics and increased durability.
Key Properties of Hempcrete
Mechanical Properties: Hempcrete generally exhibits low mechanical performance, specifically compressive strength, which is typically around 0.3 MPA. This limitation means it cannot be used for load-bearing structures. However, its low density (around 415 kg/m3) and resistance to cracking under movement make it suitable for use in earthquake-prone areas.
Thermal Properties: Hempcrete is an efficient insulating material with an R-value ranging from 0.67/cm (1.7/in) to 1.2/cm (3.0/in). It has low thermal conductivity, ranging from 0.05 to 0.138 W/(m⋅K) or 0.06 to 0.6 W m−1 K−1. Its porosity is high, ranging from 71.1% to 84.3% by volume or 68–80%. Hempcrete also acts as a moisture regulator, with high water vapor permeability, allowing it to absorb and release humidity.
Other Properties: Hempcrete is mold resistant, insect free, and fire resistant. Limecrete, Ltd. (UK) reports a fire resistance rating of 1 hour per British/EU standards. It also offers excellent acoustic performance. The high silica content in hempcrete makes it more resistant to biological degradation than other plant products.
Benefits of Building with Hempcrete
Hempcrete offers numerous benefits that align with Biofibre Build's commitment to sustainable building:
It is easier to work with than traditional lime mixes and acts as both an insulator and moisture regulator.
Due to its lack of brittleness, it does not need expansion joints.
When used in prefabricated blocks, hempcrete acts as a carbon sink throughout its lifetime. Hemp absorbs CO2 while growing, and hempcrete continues to store it through carbonation. Its net life cycle CO2 emissions are estimated to be between -1.6 to -79 kg CO2e/m2.
It provides high vapor permeability, allowing for better control of indoor temperature.
Hempcrete is a lightweight material.
It utilizes sustainable materials and can be made from locally sourced hemp.
Biofibre Build recognizes these benefits and aims to incorporate such bio-based materials into projects to offer faster installation, potentially contributing to cheaper labor and quicker time on the market. The carbon-efficient nature of hempcrete also aligns with our goal of providing solutions that can potentially benefit from Carbon and Tax Credits.
