Hemp shouldn’t be used at ground level, or it loses its resistance to mold and rot. Lime plaster coatings or magnesium oxide boards have to be applied to anything touching hempcrete, or the lime will calcify it and lose its ability to absorb and release water.
While that sounds like a lot of work, Ms. Beckerman pointed to the long-term payoff.
“In many climates, a 12-foot hempcrete wall will facilitate approximately 60-degrees indoor temperatures year-around without heating or cooling systems,” she said. “The overall environmental footprint is dramatically lower than traditional construction.”
There still aren’t international standards for building with hemp, or codes regulating how it should be used structurally or safely. ASTM International, a technical standards organization, formed a committee to address this in 2017.
Nonetheless, the use of hempcrete is spreading. A Washington State company is retrofitting homes with it. Left Hand Hemp in Denver completed the first permitted structure in Colorado last year. There’s Hempire in Ukraine, Inno-Ventures in Nepal. Israel’s first hemp house was constructed in March on the slopes of Mount Carmel.
Down south, New Zealanders turned 500 bales of Dutch hemp into a property that fetched around $650,000. In Britain, HAB Housing built five homes with hempcrete last year. Canada’s JustBioFiber recently completed a house on Vancouver Island with an interlocking internal framed hemp-block inspired by Legos.
It’s a niche but growing sector of the cannabis market. In 2015, the Hemp Industries Association estimated the retail market at $573 million in the United States.
“When I started Hempitecture in 2013 and presented the concept, venture capitalists laughed at the idea,” said Matthew Mead, the founder of Hempitecture, a construction firm in Washington. “Now there are over 25 states with pro-hemp amendments and legislation, and the federal farm bill has its own provision supporting the development of research toward industrial hemp.”
One major issue is cultivation. Although it has been legal to grow hemp in Canada since 1998, farmers need to apply for licenses. In Australia, industrial hemp agriculture has been legal for over 20 years.
In the United States, a provision in the farm bill removed hemp grown for “research purposes” from the Controlled Substances Act. Farmers and researchers in more than a dozen states can now import hemp seeds. The Industrial Hemp Farming Act, pending in the House for the seventh time, would exempt hemp plants in toto from the controlled substance designation, an Olympic leap toward a burgeoning agro-business.
Much like the “pot-repreneurs” who set up marijuana dispensaries a decade ago, before laws were definitive, a generation is pushing ahead despite uncertainties.
Sergiy Kovalenkov, 33, a Ukrainian civil engineer who spent the last three years building hemp structures and consulting on projects in Ukraine, France, Sweden and Jamaica, is beginning a project in California. The hardest steps, Mr. Kovalenkov said, are paperwork, permits and seeds.
“Building codes vary from state to state, with regulations in terms of fire and seismic activities,” he said. “If we’re talking sustainable product, seeds cannot come from Poland or France. It has to come from California.”
Only one facility in the United States processes hemp stocks, in North Carolina. Mr. Kovalenkov’s firm, Hempire USA, has also devised its own fiber separation system. “The demand is going to be quite big in the next three to five years,” Mr. Kovalenkov said.
But what does a hemp house smell like?
“It smells like comfort,” Mr. Kovalenkov said, laughing. “It smells a little like lime. We’re using the stock. You cannot smell cannabis — it has nothing to do with smoking weed or cannabis plants. It’s an industrial agriculture crop.”
In October, representatives from 14 countries attended the seventh annual Hemp Building Symposium at the International Hemp Building Association in Quebec. Terry Radford, the president of JustBioFiber Structural Solutions, an I.T.-pro-turned-tinkerer, unveiled a prefab hemp composite that could be more attractive to city planners and government building code officials.
“The problem with hempcrete right now,” he said, “is each one has to be inspected and have an exemption from the building code. It’s difficult for builders to get approved. If you’re trying to get a mortgage on your house, it’s pretty restrictive. That’s our biggest challenge.”
“Our idea is to get the material certified by building coders, rather than have each one approved,” he added. “The difference between hempcrete and my block product is that we’re a structural product. Hempcrete by itself is just an insulation.” The start-up is preparing to produce a 112,000-square-foot facility in British Columbia.
Mr. Mead, the head of Hempitecture, echoes the concerns of others. For farmers to expand, he said, the infrastructure has to be there. Without a network to process materials, “it will be difficult for farmers to know if they can grow this crop and turn a profit.”