Houses Hewn from Hemp?

Back To News
July 2, 2018
Hempcrete. Photo courtesy of GreenBuilt.
Hemp is making a comeback in the U.S. in more ways than through the legalized use of marijuana for recreational and medicinal purposes. It is undergoing a revival as a building material. While both George Washington and Thomas Jefferson grew hemp on their plantations in the 1700s, it was outlawed in the U.S. starting in the 1930s (but never in Europe). But recently, The Industrial Hemp Farming Act of 2018 was introduced in the Senate by Majority Leader Mitch McConnell (R-KY), Senator Rand Paul (R-KY), Senator Ron Wyden (D-OR), and Senator Jeff Merkley (D-OR). The bill would allow hemp to be regulated as an agricultural crop, as well as encourage federal research funding for hemp’s industrial uses. Congress must pass a farm bill by the end of September, when the current law expires.

Canada has been exporting hemp to the U.S. for several years. Today, 34 states have enacted hemp bills, and 19 states grew hemp in 2017.

Mixing hemp’s woody core with lime and water results in a natural, light concrete that retains thermal mass and is highly insulating. Its proponents say it has good acoustics, provides low humidity, and requires no pesticides. It also grows from seed to harvest in about four months. It can be made into fiberboard, roofing, flooring, wallboard, caulking, cement, paint, paneling, particleboard, plaster, plywood, reinforced concrete, insulation, insulation panels, spray-on insulation, concrete pipes, bricks, and biodegradable plastic composites.

Both marijuana and hemp are of the cannabis sativa species, but hemp is cultivated for its fiber, hurd, and seeds, and contains just 0.3 percent of tetrahydrocannabinol (THC), the compound that leads to a high.

At least 25,000 products are currently made of hemp, including apparel, foods, plastics, skin products, and dietary supplements. And now it is gaining attention as a nature-friendly
alternative to fiberglass insulation. It is nontoxic, fireproof (no, it won’t go up in smoke, as some joke), carbon-capturing, and mold- and pest-resistant.

Hempcrete or hemplime, developed in France in the 1980s, is made from the inner woody core of the hemp plant that is mixed with a lime-based binder and water. This produces a lightweight insulating material weighing an eighth of the weight of concrete.

Currently, there are said to be only 50 homes in the U.S. that have used hemp insulation and/or exterior or interior walls, but it has been used in construction around the world for hundreds of years. Hemp Technologies Global was involved in what has been claimed to be the first modern hemp home in the U.S., built in 2010 for Russ Martin in Asheville, NC.

Just BioFiber, founded in Calgary, Alberta, in 2014, has patented prefabricated structural building blocks made from hemp.

ASTM International formed a committee in 2017, D37, to create technical standards and guidance regulating cannabis and its products and processes. RCI member Ralph Paroli, past chairman of the board of ASTM and director of research and development in measurements science and standards at the National Research Council of Canada, is chair of the committee.