Hemp has been making increasingly bigger waves in the construction industry due to its sustainable and eco-friendly properties. As a content writer with a passion for sustainability, I've been exploring innovative solutions that not only inform but also create awareness about sustainable practices. In this post, we'll dive into the world of hemp-based building materials, an avant-garde concept that’s reshaping the construction industry.
Hemp = Construction Material?
After processing, the stalk of the hemp plant makes two different types of fiber: a bast and a hurd. The bast, which is used for paper and fabric, is a longer fiber and found in the skin of the stem. Hemp hurd (also known as shivs) is the soft, woody, highly absorbent core of the stalk and comprises shorter fibers. Making up about 70% of the stalk, hurd is what is used for construction materials since it has a high silica content which allows it to bond well with lime.
Forms of Hemp for Construction Material
There are quite a few building products that can be made from hemp. Probably one of the most well-known, “hempcrete”, is a generic term for a bio-composite made from hemp hurd, water and a lime binder. There are a number of trademarked variations for hempcrete, such as Canobiote, Canosmose, Isochanvre and IsoHemp. Hempcrete is a non-load bearing material and thus cannot be used as a structural element, but is utilized to form thermal walls of framed buildings. An advantage of its low density is that it is resistant to cracking under movement, which makes it perfect for areas prone to earthquakes. Depending on the ratio mix of its different variables, hempcrete can be used as roof, wall and/or slab insulation.
HempWool is a type of insulation made from hemp fibers. To make HempWool, the fibers of the hemp plant are spun into a yarn, which is then woven or felted into a fabric. HempWool is constructed of roughly 92% hemp fiber and 8% textile fiber binder. HempWool can be used as insulation for walls by being cut to fit standard wood framing dimensions, as well as in between floor joints to make floors more quiet.
Another fascinating example is HempWood, a sustainable alternative to traditional hardwoods. Produced in Kentucky, HempWood is made from compressed hemp fibers, creating a durable wood substitute. This innovative material can be used for flooring and as wooden beams, reducing the need for deforestation. Additionally, it doesn’t warp and is 20% stronger than oak wood. Greg Wilson, who patented the process used to create HempWood, explains that the company subjects the hemp fibers to high heat before compressing them in molds with a soy-based adhesive, or wood glue.
Hemp Plastics: The cellulose of the hemp plant can be combined with other materials to create bioplastics, which can be used for various building components such as window frames, roofing tiles, and structural elements.
Hemp Roofing Materials: Some companies have developed roofing shingles and tiles made from hemp fibers, providing an eco-friendly roofing option.
Hemp Oil-Based Finishes: Hemp seeds are pressed to produce hemp seed oil, which can be used as a wood finish, deck stain and a drying agent in paints.
Particleboard/chipboard: Particleboard based on hemp mixed with other fibers such as flax is lighter, stronger and more moisture resistant than its conventional counterpart.
Examples of Hemp-based Construction
Marks and Spencer, England
Opened in August 2012, M&S Cheshire Oaks has won multiple awards and is their biggest, greenest store. It has been designed to be the most carbon efficient store of theirs to date with an architectural and design strategy to address various areas of sustainability at once. It is the first store to use hemp and lime external wall panels which have excellent insulation properties resulting in the store losing less than 1°C of heat overnight compared to 9°C in other store environments.
Pierre Chevet Sports Center, France
Paris studio Lemoal Lemoal has built the Pierre Chevet Sports Center used hempcrete blocks, and is France’s first government-sponsored hempcrete building. Just outside Paris, the 4,000-square foot building includes an exercise hall and changing rooms. According to reports, the architects chose to build the gymnasium from hempcrete rather than the typical concrete due to its thermal and acoustic properties. The hemp panels used were also grown and fabricated within 300 miles of the construction site, minimizing transportation emissions and helping the local economy.
The Hemp Hotel, South Africa
South Africa has taken a defining step towards an environmentally sustainable future with the construction of a new 12-storey building in Cape Town, which will be the world’s tallest building constructed from hempcrete blocks and other hemp building materials. Adequately known as the ‘Hemp Hotel’, it is expected to open its doors to the public by year-end. The original five-storey building was bought by Hemporium’s co-founder Duncan Parker in 2016, and the exciting project has been undertaken by hemp producer Hemporium in partnership with Afrimat Hemp and Wolf + Wolf Architects. Once complete, the hotel will house approximately 50 apartments as well as Hemporium’s flagship store.
Advantages of Hemp-Based Building Materials
Environmentally friendly: Hemp-based materials have a much lower carbon footprint in comparison to traditional building materials. They absorb carbon dioxide during growth and can store it in the construction, making them carbon negative.
Energy efficient: Hemp-based materials provide excellent insulation, reducing energy consumption in buildings and lowering heating and cooling costs.
Safety conscious: When mixed with lime in hempcrete construction, hemp blocks offer up to 2+ hours of fire resistance depending on the finish and the thickness of the block used.
Renewable resource: Hemp is a fast-growing plant that can be cultivated annually, ensuring a sustainable source of building materials. In most cases, hemp fiber is ready to harvest within 120 days after planting. However, this does depend on the specific strain, cultivation practices, and climate conditions. Industrial hemp grown for its fiber typically requires a longer duration.
While hemp-based building materials offer numerous advantages, there are still some challenges to overcome. Regulations and awareness play a significant role in the widespread adoption of hemp construction materials. Another challenge is that there isn’t a lot of technical know-how on building with hemp since the material is not yet that common. A hemp-savvy architect, engineer or consultant from a hemp products maker will need to be involved, as the materials have distinct specifications and construction requirements
Government and Industry Support
Governments worldwide are beginning to recognize the potential of hemp in construction and organizations like The International Hemp Building Association are promoting its use and development. These initiatives include programs to encourage the use of hemp in construction and research and development efforts to improve the performance and sustainability of hemp-based materials.
The UK government has launched a program to promote the use of hemp in construction, providing funding for research and development projects. The European Union also supports the use of hemp in construction, funding research and development projects and programs to promote its adoption.
In the US, The Hemp Building Foundation submitted paperwork to the International Residential Codes (IRC) in February 2022 to certify hempcrete as a national building material, which has finally been approved for US residential building codes. Specifically, the certification allows hemp-lime (hempcrete) to be used as a standard material in residential construction beginning in 2024 and applies to one- and two-family dwellings and townhouses.
The Bottom Line
As someone deeply committed to sustainability, exploring the world of hemp-based building materials was informative and inspiring. These materials are not only environmentally friendly but also practical alternatives to traditional construction materials. Although there are challenges to overcome, hemp-based building materials definitely remain the way of the future.