Hemp long has been considered a brilliant form of insulation. Now “Hempcrete,” a concrete-like mixture that is a combination of hemp hurd — the wooden core of the cannabis plant — with water and lime. While not a direct substitute for concrete, hempcrete has the potential to make homes healthier for people and the environment.
Some forms of insulation are culled from fossil fuels and leave a large carbon footprint. And when one considers the energy needed to power and heat them, buildings account for almost 40 percent of global carbon emissions. John Washington, a Buffalo organizer for the Homes Guarantee campaign, says that climate mitigation efforts both concern both issues.
In addition, certain building materials pollute interior air, releasing volatile organic compounds (VOCs) such as formaldehyde, a carcinogen and other dangerous chemicals, lead and asbestos, etc. These still can be found years after they are banned, especially in homes for people of color.
Sometimes the attempt to retrofit those houses can involve the use of petrochemicals.
Hempcrete is popular with green builders, appearing in houses from Cape Town, South Africa, to Cambridgeshire, U.K. to Asheville, North Carolina. With the Biden team vowing to retrofit and build millions of homes to combat the climate crisis, sustainable materials such as hempcrete are sure to gain popularity in the U.S.
As building amps up, the question remains: Can hempcrete be affordable?
Hempcrete is much like a “sponge,” stated Benoît Savourat, a French farmer and the president of the hemp growers’ coop La Chanvrière de l’Aube. (“Chanvre” translates to hemp in French, and l’Aube is the region of northeastern France where the cooperative is located.) It absorbs moisture from the air in times of humidity and releases it in times of dryness. That plays a part in attaining the “felt temperature” of a room.
In a humid environment, it must be heated to 70 degrees or more, said Savourat. In a hempcrete-insulated home, you’re comfortable at 65.
Summer air isn’t as sticky, rendering it tolerable sans air conditioning. That means less energy use throughout the year, and could make a difference as summers get hotter.
Hemp’s true advantage in the fight against climate change, comes in the form of the carbon it absorbs during its life cycle. In a growing season of approximately eight weeks, an acre of the crop can sequester 10 tons of CO2 — more than an acre of trees can absorb in a single year.
Different components of the plant can be applied to various uses. Industrial hemp has been grown for its sturdy exterior fibers, which can be used to make textiles, pulped into paper, or morphed into forms of plastic. That leaves the interior core, or hurd, which is the primary ingredient of hempcrete. Mix the hurd with lime, a powder taken from limestone which serves as a binder, and you conjure the sustainable building material.
Once blended, hemp and lime absorb carbon, offsetting emissions from other building materials. And, as hempcrete is not a structural material, materials such as wood, steel, or concrete are needed to supply foundations and a frame. And according to analysis at Parsons School of Design, a wall with hempcrete produces approximately three times fewer carbon emissions than building a wall with traditional methods.
In Paris, social housing drives the need for more sustainable design and supply chains, says Isabelle Quet Hamon, director of sustainable development at Paris Habitat, the city’s primary social housing agency. That role, she says, cannot be separated from the agency’s primary mission of supplying quality homes for everyone.
Paris Habitat started the city’s first hempcrete development in 2012; a small apartment complex that remains a rarity in the single-family-dominated industry of hemp industry. Paris has added at least three additional hempcrete buildings, for a total of about 40 subsidized units, and more are coming. An eight-story, 15-unit building is in progress in the fancy 16th arrondissement, while another was finished in the neighbor suburb of Boulogne-Billancourt. More use of hemp also is expected in Paris Habitat renovations.
When it comes to hempcrete, the material can be costly—but it’s also lightweight, so costs can be saved on foundation construction. Upkeep is cheaper, as are ventilation costs.
Overall, hemp helps!
Image source: istockphoto.com