Last Updated: Sep 12, 2024
Three years ago, Mélany Fay and her husband, Antoine Mayer, bought three-and-a-half acres of land in Quebec province. Before they built their house, they constructed a small cabin from which they could explore the property and the weather conditions. "We wanted to learn how much rain and snow fell, what the winds were like, what the temperatures were, and where the sun landed," Fay says. Taking time to get to know the property enabled them to "site our future house in the best possible place." They also planted fruit trees, blueberry shrubs, and strawberry plants, "because they take years to give you fruit," she says.
To learn about building a home that would live light on the land, Fay took an ecological home design class from Solution Era. Fay, other students, and their teacher experimented with a variety of building solutions and sustainable materials. She concluded that she wanted to build a hemp house. Not a home from hemp wood (a wood-like product made from hemp used for interior face building, furniture, and flooring); nor by using blocks of hempcrete (made from mixing lime and water with the woody core of the hemp plant).
Instead, Fay and her husband decided to use loose hemp. "It's cheaper," she says. "We build the box walls with wood, then push the hemp inside to insulate the walls. Then cover it with a mix of lime, sand, and water to create a kind of stucco." Fay hired an expert to show them how to pack the hemp. Then, they mixed the hemp with lime, water, and a bit of brick powder to bind it together. It took six weeks, but they had the help of six to eight people a day (including other students from her class who wanted to learn).
"I wanted loose hemp because it's so natural," she explains. "You don't have any plastic between the house and the outside, it provides excellent insulation, and it regulates humidity." According to the New York Times, hemp-house enthusiasts tout the material for its stucco-like appearance and lack of toxicity. It also has a lower carbon footprint: a hemp house requires three times less energy to make than standard limestone concrete.
Joy Beckerman, a hemp law specialist and active in the Hemp Industries Association, also told the Times that "In many climates, a 12-foot hempcrete wall will facilitate approximately 60-degrees indoor temperatures year-around, without heating or cooling systems." An additional benefit is hemp's lower overall environmental compared to traditional construction.
Let's clear the air on the differences between hemp and marijuana. Both are broad classifications of Cannabis. Specifically, hemp is used "to classify varieties of Cannabis that contain 0.3 percent or less THC content (by dry weight)," according to the CBDOrigin.com. "'Hemp' has generally been used to describe non-intoxicating Cannabis that is harvested for the industrial use of its derived products." The Agricultural Act of 2018 legitimized the legal definition of hemp and made it legal for farmers to grow and cultivate hemp plants for a wide variety of uses.
Products from hemp have been in existence for more than 10,000 years, from rope and textiles to paper, body care, and food products, to building materials. Currently, hemp is an ingredient in more than 25,000 products. According to CNBC, the overall demand for nature-friendly construction is increasing. And hemp is gaining worldwide attention for its use as alternative insulation in homebuilding.
High-value insulation, as well as excellent air circulation, are top criteria in today's sustainable homes. Approximately 75 percent of all houses in the U.S. incorporate fiberglass insulation, a combination of plastic and recycled glass. Moreover, studies show that that nine out of 10 homes are poorly or under-insulated.
Hemp's woody pulp, when mixed with lime (as a binder) and water, is a sustainable alternative to traditional fiberglass insulation. Hemp breathes—it allows moisture to evaporate, so mold cannot grow. It's non-toxic, lightweight, and doesn't off-gas. Hemp is also unpalatable to termites.
Hemp's R-value beats that of concrete: roughly 2 to 2.5 per inch (based on the density) compared to 0.1 to 0.2 per inch of concrete. The compressive strength of hemp, however, is 1/20 that of concrete, so hemp shouldn't be used as a foundation or in load-bearing areas. Hemp's resistance to cracking makes it an excellent building alternative in earthquake areas.
Is it any wonder that hemp has been in demand as an easy-to-use, natural building material since Roman times? "A hemp mortar bridge was constructed back in the 6th century when France was still Gaul," the Times article states.
In France, hemp cultivation is legal, and the country has become the European Union's largest hemp producer. Across Canada, Europe, and England, hundreds of buildings have used hemp for wall and roof insulation. This includes a “Natural House” built by Prince Charles that uses sheep's wool and hemp insulation and is warmed by a wood stove.
In the U.S., the first modern hemp home was built in 2010 for Russ Martin, the then-mayor of Asheville, North Carolina. The 3,400-square-foot home has hempcrete walls that are 12-inches thick. The cost of each exterior wall was about $25 to $30 per cubic foot. At the time, you couldn't get hempcrete in the United States. It was illegal to grow industrial hemp because it comes from the cannabis plant. So the higher cost was partly driven by the need to import the raw materials needing from the United Kingdom. "Domestic production could cut the price tag in half," Anthony Brenner, of Push Design, told AmericanLimeTechnology.com. Thankfully, it is no longer illegal—but it will take some time for the U.S. hemp industry to grow and the costs to come down.
Meanwhile, in Quebec, Fay's home is nearly completed. The wood-framed house, with shou sugi ban window framing and hemp insulation, was designed with large windows facing south to bring in the sun. The home's thermal mass keeps the house cool in summer and warm in winter. A wood stove provides supplemental heat in winter and warms the water that runs through a heating system beneath the floors. No air conditioning is necessary during the summer. The house is solar-ready, but because Quebec electricity is so inexpensive, Fay says, they'll wait several years before hooking up the solar. They also plan to purchase an electric car.
"We're aiming to be as sustainable and self-sufficient as possible," she says. "We already have chickens and a rooster, fruit-bearing trees and shrubs, and a small garden. My husband takes care of the animals and grows mushrooms." A greenhouse will allow the couple to grow vegetables in the winter. Rainwater off the home's metal roof is used for plants. WaterSense low-flow fixtures in the kitchen and bath, and LED lights used in the evenings (as the windows bring in plentiful daylight) help reduce the couple's carbon footprint.
"We're working at changing our habits, too, like buying in bulk using our own containers, so we reduce the amount of plastic," says Fay, who makes her own soap and herbal medicines. "I had a daycare for 18 years and just retired. From this home, I want to teach children to discover a different way in which a home can be built and how to pick and enjoy fresh fruits and vegetables for pleasure and good taste. Nature is the solution."
Camille LeFevre is an architecture and design writer based in the Twin Cities.