Innovative approaches to sustainable and eco-friendly construction materials for have generated increasing interest in the potential uses of the remarkable cannabis Sativa plant. Since the passage of the 2018 US Farm Bill, cannabis plants containing less than 0.3 percent THC (tetrahydrocannabinol) are no longer classified as “marijuana” regulated under the Controlled Substances Act. This has opened new opportunities for agricultural, commercial, and industrial applications utilizing the plant and its products.
Known more specifically as industrial hemp, the non-psychoactive variety of the cannabis plant has played a role in producing medicinal CBD (cannabidiol) oil and is finding an increasing array of material uses, ranging from paper and bioplastics to biofuels and construction materials.
As the climate crisis intensifies, architects and engineers search for new materials and designs that can reduce the construction industry’s impact on the environment. According to a 2022 status report from the UN, the building and construction sector accounted for around 37% of global energy and process-related CO2 emissions in 2021. Familiar building materials like concrete and lumber require intensive carbon emissions and water use for their production.
Strangely, hemp is emerging as a potentially critical product for sustainable construction solutions. Recent efforts by researchers and innovators have revealed interesting properties of hemp that indicate its potential as a reliable and more sustainable alternative to materials like concrete or lumber.
For one, hemp helps protect the environment because hemp can sequester more carbon from the atmosphere than most crops, including trees. The fast-growing plant captures significant amounts of carbon over its lifetime to form a substantial woody stalk. When manufacturing utilizes parts of the plant, the artifact further captures this carbon instead of it returning to the atmosphere. Hemp becomes a carbon-negative crop when managing agricultural and production tools sustainably, so constructing with hemp helps extract carbon from the atmosphere and encapsulate it in durable building materials.
Processing hemp transforms it into lumber replacement products such as plywood, boards, and wood planks with a hardness comparable to oak. Unlike lumber, which takes about 40 years to renew, hemp crops can renew in just 90 days. Additionally, hemp serves as a lightweight and efficient insulation option, presenting a lower carbon footprint compared to conventional synthetic materials like fiberglass and foam board. Furthermore, hemp can be processed into blocks or panels for substituting concrete in walls or floors.
The sturdy hemp-based building material known as “hempcrete” (also known as lime hemp concrete), has emerged as a desirable construction option for people wanting to build more planet-positive housing. Although hempcrete was first produced in France in the 1990s, and people have been building with hemp for centuries before then, construction certification issues and strict agricultural licensing requirements surrounding hemp crop cultivation have historically prevented researchers and builders from making much use of the product until recent passage of new agricultural laws.
Hempcrete is made by mixing the pulp of the plant’s head, which is the woody core of the stem, with a binder made of water and lime. The product is lightweight relative to other building materials, yet highly physically durable. However, hempcrete cannot structurally support load-bearing walls. Instead, builders use a frame constructed from timber or concrete, and they assemble the hempcrete blocks and panels around the structure. Although building with hempcrete doesn’t cut resource-intensive concrete from the building process entirely, the use of hempcrete walls does ultimately cut down the use of concrete, plastic, and wood components in favor of more sustainable materials overall.
Because hempcrete has a high thermal mass, the product is also an ideal insulation material with the ability to improve the energy efficiency of buildings, which serves to reduce greenhouse gas emissions over time. Some of the other many advantages of hempcrete include moisture regulation properties as well as resistance to fire, rot, and insect infestations.
With its inspiring versatility and remarkable potential, hemp is emerging as a game-changer in sustainable housing solutions. The coming years will see the production of more hemp homes, hemp housing communities, and more advanced hemp alternatives for construction materials. For example, there are currently over 50 hemp homes in the United States, and work has begun on a residential project in Massachusetts created from hemp-lime panels, which will be the largest hempcrete dwelling in the United States.
Hemp homes are even rising in international popularity, with 2020 producing a seven-story block of hempcrete-insulated housing in Paris. A high-rise building under construction in Cape Town, South Africa is set to be the world’s tallest building made of hempcrete. With progress underway, it is likely that in the not-so-distant future, hemp housing and alternative construction materials will not only build homes for individuals, but these materials will also serve to contribute to the larger global aim for sustainability and responsibility for our collective environmental impact.