Building with Hempcrete

By Tobias Roberts,Rise Writer

Last Updated: Jun 6, 2021

As many states move to legalize recreational and medicinal marijuana, the motivation to extend this legalization to industrial hemp is also gaining steam. While hemp is a relative to recreational marijuana, it contains less than half of one percent of THC (tetrahydrocannabinol). Hemp is cultivated for its woody core that offers a sustainable and renewable alternative to cement.

The H.R.3530 Industrial Hemp Farming Act of 2017 has been introduced to Congress. It would allow hemp to be regulated as an agricultural crop instead of as a controlled substance if passed. In 2018, over 77,000 acres of industrial hemp were grown across the US. That number is expected to surge in the coming years as regulations ease, and the benefits of hemp are realized.

What is Hemp?
What is Hempcrete?
What is Hemp Hurd?
What is a Lime Binder
What is the R-value of Hempcrete?
How Strong is Hempcrete?
How Long Does it Take to Grow Hemp?
Insulating with Hempcrete,Alternative Uses For Hempcrete
What are The Advantages of Hempcrete?
What are The Disadvantages of Hempcrete?
What Are the Sustainability Benefits of Hemp for the Building Industry?,Where to Buy Hempcrete Products
Bottom Line

What is Hemp?

Hemp is a relative of the marijuana plant without high concentrations of THC. It is also one of the fastest-growing biomasses on the planet. The thick, woody pulp of the hemp plant offers many different uses. The textile industry can use industrial hemp for making clothing and footwear and as an alternative building material. Hemp can also be used to make paper, oil, soap, and other beauty products, protein flour, food supplements, biodegradable plastics, and biofuel.

What is Hempcrete?

Hempcrete was first used in construction to build non-weight bearing infill walls in France during the early 1990s. Hempcrete is made from mixing the hemp hurd with lime and water and weighs only about an eighth of regular concrete weight. The lightweight nature of hempcrete can also reduce the embodied energy of a building by reducing the emissions associated with transporting heavy materials. Since industrial hemp can also be grown in a wide range of climates and soils, it is also an excellent alternative as a local building material.

What is Hemp Hurd?

Hemp herd is the soft, woody, highly absorbent core of a hemp stalk. They are available in various grades and are a natural by-product after the hemp stalk has been stripped. Hemp hurd is sometimes referred to as hemp wood or shives and is comparable to shives in flax. A process called scutching helps separate impurities from the raw material.

What is a Lime Binder

Descended from limestone, a lime binder acts as a bonding agent. It has been used in mortar and plaster construction for thousands of years. It's available in various grades and types and mixing ratios, impacting its durability, strength, and setting time.

What is the R-value of Hempcrete?

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. The thermal performance of hempcrete can be impacted by several variables, including the type of binder used, moisture contents, and density.

How Strong is Hempcrete?

The compressive strength of hempcrete is 1/20 that of concrete, coming in at 1 MPa, meaning it can't be used as a foundation material or in situations where it may be load-bearing. It's resistant to cracking due to its low density making it an attractive alternative to areas prone to earthquakes.

Hempcrete also breathes, allowing moisture to evaporate (no mold), does not off-gas, and is avoided by termites. The non-toxic and lightweight properties of hempcrete also ensure it is easy to move around a job site.

While hempcrete may be growing in popularity, it's still not widely available on the market. Nonetheless, hempcrete has a comparable cost to other insulation options and will become more affordable as production volumes increase.

How Long Does it Take to Grow Hemp?

Hemp fiber and seeds are usually ready for harvest in two months. The rapid growth rate allows it to outcompete other raw materials because it is rapidly renewable and can be used in a wide variety of diverse industries. For example, hemp can produce about four times as much paper as trees per acre. The difference, of course, is that trees take years to reach maturity.

Insulating with Hempcrete

The woody pulp of the hemp plant also offers several potential applications for the sustainable building industry. About 75 percent of all homes in the United States rely on fiberglass insulation, a mixture of plastic and recycled glass. Unfortunately, studies have found that nine out of every ten households in the country are also under-insulated.

Increasing our homes' insulation is an important strategy to improve energy efficiency. There are several healthier insulation products on the market, from wood-based insulation to insulation made from sheep's wool. When mixed with lime (as a binder) and water, hemp's woody pulp also offers an alternative to fiberglass insulation. Prince Charles of the United Kingdom recently built a "Natural House" that relies entirely on sheep's wool and hemp insulation and is warmed by a single wood stove.

Alternative Uses For Hempcrete

Hemp can be used to manufacture structural blocks and prefabricated panels for exterior walls. Unlike regular bricks or cinder blocks, these exterior wall products increase the R-value by incorporating thermal performance into the structural component of your home as well. Hempcrete makes an excellent insulation alternative to subfloors, walls, attics, providing it isn't exposed to excessive quantities of moisture or water. Hemp plaster is another everyday use. It gives the benefit of sealing and rain protection with the beautiful aesthetic of conventional stucco. In recent years, hemp has also been used to produce cabinets and countertops.

What are The Advantages of Hempcrete?

Hempcrete breathes, allowing moisture to evaporate (no mold), does not off-gas, and is avoided by termites. The non-toxic and lightweight properties of hempcrete also ensure it is easy to move around a job site. Hempcrete does not shrink, maintains a steady temperature, and can also increase in strength over time.

What are The Disadvantages of Hempcrete?

While this may not qualify as a real disadvantage, hempcrete cannot be used as a foundation structure due to its low compressive strength. In most cases, it is not a load-bearing material. A project that could utilize a lightweight foundation could take advantage of hempcrete instead of concrete, providing it adheres to local building codes and is approved by an engineer. While research and development around the use of hempcrete are still in infancy, preliminary findings are incredibly positive.

What Are the Sustainability Benefits of Hemp for the Building Industry?

Because of its fast growth, structural blocks and panels made from hemp and hempcrete could become an alternative to more traditional cement blocks and timber framing. This could reduce pressure on forests worldwide and cut back on the estimated 15 billion trees cut down each year. Less deforestation would also lead to increased carbon capture, thus offering a natural way to combat global warming.

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.

Hemp is also naturally fire-resistant and mold resistant. Thus, builders can reduce reliance on chemical fire retardants that have been linked to several health problems. Hemp offers the sustainable building industry a bio-based product that is virtually carbon neutral and can be used in many building applications. Hemp can be locally produced as a renewable agricultural resource and doesn't require multiple agrochemical products. It can also be an important crop to reactivate and strengthen rural economies.

Where to Buy Hempcrete Products

Across the Atlantic, where hemp has faced less stringent legal implications, several European firms have specialized in providing a wide range of hemp building products.

Hempitecture

While hempcrete, hemp insulation, and hemp building blocks offer numerous sustainability advantages, specific construction requirements must be followed due to hemp's lightweight nature. Finding a builder with experience in hemp building is essential. Hempitecture is one company that offers its services across the US with a hempcrete installation. Tiny Hemp Houses is another Colorado-based company that specializes in building tiny homes from hempcrete.

ISOHemp

ISOHemp is a Belgian company that offers a wide range of hempcrete blocks as a sustainable masonry alternative. Their products are geared towards new build or renovation projects spanning residential, commercial, and industrial buildings. They manufacture over 1 million hemp blocks per year and have 2,000 pallets of stock ready to go at all times.

Hemp Tech Global

Hemp Tech Global is another company that can help with designs, builds, logistics, and personnel for hemp-built homes. As hemp continues to gain momentum in the United States as a renewable alternative for the building (and other) industries, local suppliers and manufacturers should emerge. However, suppose you currently have a hard time finding a hempcrete supplier in the United States. In that case, Hemp Tech Global can help you source large amounts of hemp hurd (which can then be made into hempcrete) from international suppliers for around $17.40 for a 15 kg bag.

American Hemp LLC

American Hemp LLC is another company that has taken the lead in promoting hemp as an alternative building material. They source hemp grown in North and South Carolina. American Hemp can offer processed hemp material separated and converted into long hemp bast fibers, short fibers, hurd (core), and dust (fine) ready for purchase.

American Lime Technology

American Lime Technology can design, manufacture, supply, and install factory-made (pre-dried) Hembuild® panels. They also offer a hemp-based exterior cladding option for sustainable homes.

Bottom Line

The benefits and potential uses of hemp in the building industry make it worth checking out as the trend continues to grow and becomes widely available. At Rise, we like hemp because it represents just one of many innovative, more sustainable products in the building industry—a bright spot for our future!

Disclaimer: This article does not constitute a product endorsement however Rise does reserve the right to recommend relevant products based on the articles content to provide a more comprehensive experience for the reader.Last Modified: 2021-06-06T16:37:25+0000

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.