Green Builders Are Using Hemp
When the public Pierre Chevet Sports Hall opened last year in Croissy-Beaubourg, a small municipality on the outskirts of Paris, it was the first commercial project in France constructed almost exclusively of hemp blocks.
Many hemp enthusiasts predict this is just the beginning. Sonia Sifflet, lead architect on the project for Lemoal Lemoal, a boutique architecture firm in Paris, said she expects to see many more hemp block projects in France.
“In five years, it will be normal to use hemp blocks,” she said. “There is no limit to what can be built.”
Interest in hemp as a substitute for construction material is growing as developers seek greener options. Hemp can be used in block form, or poured like concrete using hempcrete, a combination of lime, hemp fibers and a chemical binder. Hemp panels can also be used.
But hemp construction is hampered by high costs and a supply chain that is not fully formed. And proponents must overcome resistance to a product that is often mistakenly tied to recreational drug use.
Advocates say hemp offers many benefits that builders and policymakers seek when creating a carbon-neutral product that is resistant to fire, mold and weather.
Ms. Sifflet added that hemp blocks require no special skills to assemble, reducing the number of workers needed on site. “They go together like Legos,” she said.
The simplicity allows for speed: A building constructed from ready-to-use hemp blocks can chop 20 to 30 percent off the typical production schedule.
Ms. Sifflet said that using hemp blocks pushed the material costs 30 to 40 percent higher than cinder blocks, but the quicker production schedule allowed the firm to wrap up faster than usual, and the environmental gains offset some of the higher material costs.
In Cape Town, South Africa, the first hemp skyscraper, called 84 Harrington, is being built, and, at 12 stories, will be the tallest structure in the world that incorporates largely hemp construction.
Duncan Parker, a co-founder and the chief executive of Hemporium, a hemp producer in Cape Town, and the owner of the skyscraper, said that the cost of building 84 Harrington was higher because hemp had to be imported from England. But the first hemp cultivation licenses in South Africa were issued in 2022 and the first crops will be harvested next year, allowing for blocks to be made there.
“We are building an industry,” he said, adding that it will take a couple of years for supply issues to sort themselves out, but once they do, hemp will be a construction staple.
Don Redden is the chief executive of Ulmus Development, which is building a self-storage site made from hemp blocks in Kelowna, a city of 130,000 in British Columbia, Canada.
Mr. Redden said the building’s carbon equation tilts negative because it will actually draw carbon from the environment. He said each hemp block would sequester about six kilograms of carbon, more than what is expended in the making and shipping of the blocks.
Rachel Berry, the founder of the Illinois Hemp Growers Association, said the first step to increasing hemp construction in the United States is getting farmers interested, but hemp’s cannabis connection can make them reluctant.
“The stigma of cannabis still looms here,” she said.
Climate-friendly construction, but with a stigma.