The cannabis plant is getting a lot of attention these days as states legalize the use of marijuana, but there’s another corner of the hemp market that’s shaking up the construction industry, hempcrete. It’s a green building material that dates back to the time of the Romans in Europe, but is just gaining acceptance here in the United States.
The New York Times just cast a spotlight on the use of hemp as a building material with an article called, “There’s No Place Like Home, Especially if It’s Made of Hemp.” The attention is well-deserved with all the benefits that hemp provides for a construction project (1).
Not only is hemp used to create a concrete-like building material, it’s also a fast-growing, sustainable plant. Crops mature in about 4 months. The woody fibers are then mixed with water and lime. When they cure, the result is a strong, lightweight material that is resistant to fire, mold and bugs. It’s also breathable and non-toxic with no off-gassing, and provides exceptional insulation.
Putting Hempcrete to Use
The hemp mixture is generally used to fill a wood-framed structure with plywood boards screwed into the frame to form a mold. The hempcrete is tamped down behind the boards, and allowed to cure for short amount of time before the boards are removed. Hemp can also be used to insulate roofs and floors with some amount of airspace to help increase its insulating qualities.
The hempcrete will keep its shape and will get stronger over time. The National Hemp Association said, it eventually hardens into a substance that can last for hundreds of years, but it isn’t generally used alone for load-bearing walls, unless its combined with a wooden frame.
Since it does gain strength over time, builders can use hempcrete blocks or bricks that have been cured for a longer period of time. The Association said, blocks that are “suitably cured” can be used just like regular bricks without the need for a wooden frame (2).
It’s taken decades for hemp to get this kind of recognition because it’s been banned since the 1970s. It was declared illegal as part of President Richard Nixon’s “War on Drugs.” The newly formed Drug Enforcement Agency lumped industrial hemp into the same controlled substance category as its high-inducing cousin.
As of 1998, hemp farming was still illegal in the U.S. but businesses were allowed to import hemp from other countries. This recent wave of state marijuana legalization has also opened up doorways for hemp production and the use of hemp products. In 2013, Colorado was the first state to legalize the farming of industrial hemp.
In 2014, President Obama signed the Farm Bill, which included a section defining industrial hemp as distinctly different than the kind you smoke at a music festival. It also made it legal, at the federal level, to cultivate hemp for university research purposes in states where hemp was also made legal.
Hemp research and production have come a long way since then. At least 34 states have now redefined industrial hemp as something completely different than marijuana. The federal policy on drugs remains as it was, however, without that distinction, so farmers are still at risk of a federal crackdown on pot for growing hemp.
Related but Different
Hemp is still a misunderstood product in the U.S. because it’s related to marijuana. They are both cannabis plants of the sativa variety, but industrial hemp has less than .03% of THC, which is the component that makes you high, and marijuana has more than .03% of THC. The Ministry of Hemp said, the THC content of marijuana is typically between 5% and 35%.
The two kinds of cannabis are also similar in appearance with 7 leaves, but industrial hemp leaves are skinnier, with more leaves at the top of the plant and fewer branches. The Ministry of Hemp said, marijuana looks like a short fat bush from far away while hemp looks much taller and thinner.
Cannabis Popularity Grows
Cannabis popularity prevails, though, and many botanists and builders are experimenting with hempcrete. The New York Times reported, the first hemp house was built in North Carolina 8 years ago, and there are now about 50 hemp homes in the country.
Builders need special permits to use hemp for construction, and the rules vary from state to state. Plus, much of our hemp needs to be imported because U.S. farmers are not producing much hemp, yet.
The Times estimated, just 10,000 acres are being used to grow hemp in this country, while Canada has twice as many acres dedicated to hemp. Outside North America, about 30 nations are producing hemp. In China, 10,000 farmers are growing it.
It’s a fascinating material with many benefits and will likely get more attention over the coming years.
(2) Hempcrete: National Hemp Association