Marijuana has been in the news a lot recently — from recreational legalization to the scare tactics of Jeff Sessions — but when is the last time you heard about hemp? Colorado is home to an impressive number of hemp farms that span thousands of acres and the burgeoning question for those farmers and other interested parties are what to do with their product. There is no shortage of possibilities when it comes to using industrial hemp — paper, clothing, food, building material and more. One Colorado company is taking big strides to construct homes using hemp and will be the first one in the state to do so. Left Hand Hemp—composed of founder and CEO Kelly Thornton and hemp-event coordinator Alli Cloyd— is paving the way for hempcrete as a legitimate and common building material and want to prove just how sustainable it can be.
What is Hempcrete?
The woody core of a hemp plant. Photo courtesy of Left Hand Hemp
Processed hurd (hemp pieces) from Europe. Photo by Cori Anderson
Hempcrete is a biocomposite made of the woody interior (inner wooden core) of the hemp plant mixed with a lime-based binder. Hemp core is called hurd or shiv, and it has a high silica content which allows it to bind well to lime. The result is a lightweight, insulating material that slightly replicates cement and is resistant to fire, water, and rot. The marriage of the hemp hurd and lime produces a material that would be like trying to set a rock on fire or make it waterlogged. If that doesn’t make you stop and think for a moment, then go read some news about devastating wildfires and catastrophic hurricanes and come back.
Unlike concrete, hempcrete does not expand and contract in a way that requires expansion joints, though it breathes as an insulator so the house is cool in summer and warm in winter. It does not bear the weight of a building but rather is put between load-bearing studs and wooden frames. Hempcrete is more popular in Europe than in the United States, though there are many areas within the country that could benefit tremendously from building with it. Especially areas that are rife with wildfires, flooding, or mold.
The evolution of hemp as a building material is poorly recorded, aside from the knowledge that France began using it at least since the 1980s as a replacement for deteriorated and ancient timber-frame homes. There are many benefits to using hemp as a building material to those who are living in the home— mainly, there is almost no need for any petroleum product in the building or maintenance of the home. Hempcrete homes do not use drywall, latex paints, or forced air systems. It’s an ideal solution to those who want homes off the grid or without toxic off-gassing. Thornton remarks, “a hempcrete house breathes, it pulls air in and out passively. I don’t know why someone wouldn’t want that for their home.”
How Are Homes Built With It?
As stated before, hempcrete does not hold weight, or in other words, it’s a filler between weight-bearing studs and frames. Mixing the hurd with the lime-based binder produces a substance like soggy granola which is then padded and shaped into frames and walls. Freshly wet hempcrete takes a long time to cure, which is perhaps the biggest downfall of the substance, but in Colorado it tends to dry faster due to the arid landscape. When it cures, the hempcrete is like cement or rock and does not break down easily. To finish a hempcrete home, the walls are covered with a plaster that is made with the same lime binder in the hempcrete. This plaster can be dyed with natural tones for different colors and is necessary instead of regular paint in order to allow the hempcrete to breathe.
Left Hand Hemp has created a business model that works on teaching people how to build with hempcrete while at the same time actually building a hempcrete home for someone. Their first completed building was in Denver, where they built an artist workshop on private property. With help from a handful of volunteers, Left Hand Hemp applied hempcrete into a 20 feet by 16 feet space in only one week. “We like the idea of teaching people how to be sustainable,” Thornton explained. “Anyone can go buy a book on this subject but we offer them the chance to actually get their hands dirty and activate the information.” It’s a new take on construction— one that works better when an entire community gets involved, and it certainly expedites the process.
The Future of Hempcrete in Colorado
Hempcrete, in detail. The woody pieces are hemp hurd and the gray substance is the lime binder.
After building the private workspace in Denver, Left Hand Hemp was approached by another private landowner in Southern Colorado to build two 18 by 32 feet structures on a ranch. Construction will not begin until later this year. After building the two smaller structures, and with funding pending, a full-sized hempcrete home might be built on the property. This would mark the first full-sized home using hempcrete in Colorado and will hopefully set the stage for future development in the same fashion.
What is problematic about the future of hempcrete in Colorado, and more generally around the country, is the lack of industrial hemp processors. Currently, Left Hand Hemp sources the raw product from Old Dominion Hemp which operates out of Virginia and Minnesota and sources the processed hurd from Europe and New Zealand. This makes the cost, and carbon footprint, higher than necessary. Colorado is growing industrial hemp on a major scale, yet no one has the necessary equipment to break the plant down for manufacturing purposes. If someone were to start processing hemp in Colorado, the cost of hempcrete construction would fall dramatically, leading to an undeniable financial incentive to build with it. Until then, hempcrete may remain well out of major developers radars, circulating within the groups who already know about sustainable living and are actively seeking ways to do it.
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