Hempcrete

First, let’s talk about hemp.

Hemp, often referred to as industrial hemp, is a multipurpose plant that can be used for food, fiber, building materials, and medicinal compounds. It is one of the fastest-growing plants on earth, (hemp fiber and seeds are ready within two months!) requires minimal water, little energy to grow, promotes soil biodiversity, requires no pesticides, and can be grown in a variety of climates and soil types. Sounds like a miracle plant, doesn’t it? At one point in history, the United States government even mandated farmers grow a portion of hemp on their farms. Unfortunately, hemp was banned in 1937 during the Marijuana Tax Act due to its association with marijuana. Although, let’s be serious, there were lobbyists in favor of synthetic textile companies, which also aided in the banning of hemp production.

Let’s be clear. Hemp is a relative to marijuana but it is the stable relative… not the crazy one. For example, marijuana can contain up to 30% THC while hemp contains less than .3% THC (per dry weight).

Thankfully government officials are (slowly) changing their minds about hemp production. The problem now is we are 80 years behind where we left off. Thanks to companies like Patagonia who are promoting the use of hemp in their products we may have an opportunity to reinvent industry standards while promoting local farmers and protecting the environment.

The following video by Patagonia gives an overview of the American hemp Industry. It is well worth the watch before moving on to the hempcrete article below.

Now let’s talk about Hempcrete!

Hempcrete is a mixture of hemp hurd, lime, and water. The ratio of ingredients used will produce different qualities of product. Hemp Hurd is the innermost part of a hemp plant. Hemp hurd is soft, wood-like, and highly absorbent. Lime (limestone) has been used in building practices for thousands of years and is used as a binder. Depending on the type and quality of the lime will affect the durability and strength of the hempcrete. And of course, water, helps bind the lime and the hemp together.

After material have been mixed, the byproduct is rot-resistant, fireproof, does not off-gas or attract termites, maintains a consistent temperature, and is aesthetically beautiful! With the appropriate formwork, the mixture can be formed into blocks or cast-in-place walls. Whichever method is selected, once installed the hempcrete walls can be left exposed. No additional exterior siding or interior drywall is required. However, individuals may choose to cover the walls for a more traditional aesthetic. Hemp plaster is even an option. Due to hempcrete’s low compressive strength, it cannot be used in foundations. However, research is still underway and the capacity of this product is still being examined.

How sustainable is hempcrete?

Hemp hurd is typically a waste product in the hemp Industry so hempcrete eliminates the product from the waste stream and repurposes the material. More so, “industrial hemp absorbs CO2 from the air during its growth. After mixing the hurd with the binder, CO2 is absorbed during the solidification process ultimately offsetting the building material’s carbon footprint. 1 ft3 of hempcrete building material offsets approximately 7.27 lbeq of CO2 (Hempitecture)”. As far as performance “Hempcrete has an R-value of 2.4 to 4.8 per inch, compared to 0.1 to 0.2 per inch of concrete. Hempcrete can also achieve a higher R-value than fiberglass batt and cotton batt, whose R-values are, at most, 3.8 and 3.7, respectively (rise)”.

Since hemp is a fast-growing plant, the use of the material could greatly reduce the demand for lumber and potentially cut back on the 15 billion trees cut down each year. Trees that remain in our forest increase carbon capture which in return combats environmental degradation. “The cement industry is also one of the most significant contributors to global warming. It accounts for 5 percent of all CO2 emissions. On the other hand, Hempcrete doesn't require widespread chemical processes or the burning of fuel that release greenhouse gas emissions. The lime utilized in hempcrete as a binder can capture carbon dioxide from the atmosphere, as the lime cycle's natural chemical processes allow hydrated lime to harden into limestone (rise)”.

The future appears bright for hempcrete. It’s hard to refute a building material that has so many benefits. The United States is overdue for ‘new’ building methods that reduce and/or eliminate toxic conventional practices and produce buildings that are safe for humans and beneficial to the surrounding environment.

If you are interested in building with hempcrete I would suggest looking at Hempitecture. They are an Idaho-based company offering hemp building materials and even offer HempWool insulation.

The video below explains more about the building process of hempcrete. To see the Montana Huis made of hempcrete click the ‘project’ tab at the top of the webpage.