Imagine a material ten times stronger than concrete but only one-sixth of the weight, that removes carbon from the air, is both an insulator and moisture regulator, and can be made from a plant already grown in the United States? That plant would be hemp, and builders in Europe have been using it in the form of “hemp blocks” to build houses and other buildings for decades. Now, they are coming to America.
Hemp has a long history in construction. In fact, it is well known that Roman engineers used its fibers to enhance the mortar for bridge abutments. Hempcrete is made by mixing the woody inner lining of the hemp stalk (hemp hurds) with either lime, sand, or pozzolans. It can be found marketed under names like hemp-lime and canobiote. Hempcrete lacks the brittleness of regular concrete, removing the need for expansion joints. Unlike wood, hempcrete is naturally fire-resistant and pest-resistant. Walls made from hempcrete are very breathable and allow moisture to pass through, which makes hempcrete highly resistant to mold. Moreover, it has low thermal conductivity and wind-resistant properties, making hempcrete an ideal insulator.
The company that drew my attention to this nascent industry is HempBLOCK Australia, which just secured an exclusive distributorship in the USA for a “hempcrete” building system developed by the French firm Vieille Matériaux. Johan Tijssen, Director at HempBLOCK operations in the USA and Australia, says the bio-based system is cost-competitive with traditional construction.
HempBLOCKs arrive on-site, ready to use just like any block or brick. The interlocking blocks don’t require mortar jointing, and the company claims they can be installed up to 70% faster than building with traditional materials. Also, no special equipment is required, meaning builders skilled in existing building practices can assemble HempBLOCK walls. “In fact, it requires more skills to build with traditional brick, concrete blocks, or timber frames,” Tijssen said.
The HempBLOCK system is suitable for the construction of single-family homes and small buildings up to two stories. The blocks can also be used to insulate existing buildings, providing a rating of up to R28, Tijssen said. The company offers an in-house team of architects who help can develop basic building designs or work to advance existing plans by tailoring them to the HempBLOCK system. Learn more at HempBlock’s website HERE.
Tijssen said HempBLOCK’s U.S. and Australian units are currently importing blocks from their supplier, but the company has plans to set up manufacturing in the U.S. and Australia with its French partners. “It will be commercially viable to manufacture blocks in the U.S. when market demand and the availability of hemp are at the level required to justify investing in a local production facility,” Tijssen said. “We believe that these conditions will be met within the next two years.”
Steve Allin, director of the International Hemp Building Association, says more builders are beginning to see value in hempcrete. Buildings have been built or renovated with hempcrete in France, the U.K., Belgium, Ireland, the Netherlands, Italy, and Australia. He says the British Science Museum’s artifacts storage facility used hempcrete, as have public housing towers and even renovations on stone buildings hundreds of years old. The challenge, he says, is availability. There are only about a dozen hemp processing plants that are able to process hemp into a form usable in the creation of hempcrete, and most are in Europe.
Almost all hemp processors in the United States are equipped for CBD hemp purposes. Hemp grown for CBD is short and bushy, whereas industrial hemp for fibers and stalks are tall and reed-like. Because of their difference in size, and the difference in mechanics to process the plant, there are not many hemp hurds being produced locally in the country. But a number of fiber processing factories are going online across the country.
One of those is BastCore LLC, which is building an industrial complex near Montgomery, Alabama. BastCore just closed a $2.8 million funding round that it will use to advance its decortication and degumming technology, and add workers to meet “ovewhelming demand” for textiles and other hemp fiber markets, the company said in a press release. BastCore, which started in Nebraska in 2014, buys hemp stalks and processes them into fiber products using both the stringy bast fibers on the outside of the stalk as well as the hurd – the stem’s woody inner core. Planned outputs include different grades of bast fiber for textiles and composites; hurd for the construction industry; and “micronized core wood” (dust). The company is setting up operations in a 60,000-square-foot former steam plant on the outskirts of Montgomery. Learn more BastCore HERE.
Another large limitation for hemp as a construction material within the United States lies with the lack of certification. Without a certification for use as a building material, obtaining home insurance and building permits can be a challenge, and hurdles vary widely depending on the location. (Sources: New York Times, Ensia, HempToday, IHBA)