You’ve probably had a fever dream about living in a cannabis house (don’t lie.) But what if you actually could?
Seriously, there’s a way to build a house with weed, and it doesn’t involve sewing leaves together at a hemp farm.
It’s done with hempcrete – a mix of hemp hurds (the core of the plant’s stalk), lime, and sand (or pozzolans) which acts as a construction and insulation material (like concrete, but so much more interesting.)
Hempcrete is nothing new. The first known use of it was roughly 1,500 years ago, when, in India, it was used to create Buddhist places of worship, and the Romans built a mortar bridge from a 6th-century version of the material.
If you haven’t heard of hempcrete before, though, you wouldn’t be the only one. Hempcrete only recently reentered the construction market in the United States, since, from 1970 until the 2018 Farm Bill passed, it was illegal to produce hemp. Even today, hemp growth is highly restricted in many parts of the country, and those in the industry say the stigma around cannabis and the misconceptions about hemp in the U.S. make it a difficult product to market.
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Nevertheless, hempcrete’s popularity has been on a steady rise in recent years. In Europe, where 25% of the world’s hemp is cultivated and the laws surrounding it are looser, industrial hemp is one of the primary uses of the plant, and there are at least six major hempcrete construction companies in the U.S.
But why build your home with hemp when you could build it with, well, anything else?
According to Kelly Thornton, CEO of Left Hand Hemp, a hempcrete consultation and construction company based in Boulder, Colorado, this unconventional material has a few serious perks (besides sounding cool.)
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Hempcrete is a popular choice for those looking to reduce their carbon footprint, since it absorbs CO2 as it sets. It’s also pest-proof, since it is impossible for unwanted guests like mice and roaches to eat their way through it, and it’s one of the most breathable insulators on the market, making it resistant to mold and mildew. Additionally, hempcrete is made of completely non-toxic, biodegradable materials, which does wonders for the air quality of the home.
“Hempcrete is a fringe building media in the U.S. at the moment, but I think it could become a traditional building choice if the momentum continues,” Thornton said. “I consider it the best building material on the planet because you get all the benefits of a strong, virtually impenetrable wall without worrying about making a negative impact on the environment.”
Thornton also said hempcrete is virtually fireproof, making it ideal for those living in dry parts of the country such as California, Oregon, and Colorado, where wildfires are a major threat. This is mostly thanks to the earthen plaster in it. In an ASTM fire safety test conducted earlier this year, hempcrete received a perfect score.
There are, however, some drawbacks to consider before you ditch your house for home sweet hemp.
Hempcrete only has roughly 5% the compressive strength of concrete, so you really, REALLY shouldn’t make it the foundation of your home. Also, a 2016 study published by the Journal of Construction and Building Materials showed hempcrete can actually absorb rain, increasing mold growth and decreasing temperature control, if a coating is not used on top of it that is extremely permeable to water vapor.
Another thing to keep in mind is that hempcrete is mostly reserved for the wealthy at this point. Since there are so many restrictions on hemp farming and manufacturing in the U.S., there is a serious lack of hempcrete material in the country. This means the majority of the hemp used for industrial purposes must be imported from Europe and other parts of the world, making the material vastly more expensive than other options (roughly $60 more per square foot.)
Thornton believes this may change as hemp becomes normalized in the U.S.
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“Americans take what they are given, and currently, that is quickly built stick houses using incredibly toxic materials,” Thornton said. “It (normalizing hemp) will simply be a matter of showing people by example, which is what hempcrete companies in the U.S. are working towards. Hempcrete will become more affordable once more people see what it can do.”
Elissa Esher is Assistant Editor at GreenState. Her work has also appeared in The Boston Guardian, Brooklyn Paper, Religion Unplugged, and Iridescent Women. Send inquiries and tips to elli.esher@hearst.com.