Hemp Concrete for Construction

Hempcrete (Hemp Concrete Building Material) 101

Hemp is an incredibly versatile plant that’s renewable, sustainable, durable and eco-friendly. Many people are familiar with hemp’s use in textiles and paper products, but this plant can also be used to create hempcrete.

As you may have guessed, hempcrete is designed to mimic traditional concrete in size, shape and use. While it doesn’t possess all of the same properties as regular concrete, hempcrete is a viable alternative for a variety of applications.

What is Hempcrete?

Hempcrete is a type of building material made from hemp hurd, lime and water. It’s much lighter than regular concrete, which makes it easier to build with and also reduces emissions because you’re not transporting such heavy materials.

Hempcrete’s use as a building material dates back to the 1990s in France, where it was used to construct infill walls.

While hempcrete has many advantages as a building material, it does have poor compression strength. For this reason, it’s only used for infill walls and not for foundation construction. Hempcrete only has about 5% the compressive strength of conventional concrete.

When used for building walls, hempcrete requires structural support, such as wood framing. Block can be built at the construction site, or transported as pre-fabricated blocks.

France and Canada are both avid users of hempcrete, and the building material continues to be a popular option in the construction industry.

How is Hemp Concrete Made?

Hempcrete consists of water and two other important components:

  • Hemp Hurd: The core of the hemp stalk. The hurd, also known as shive, is a natural by-product of hemp processing.
  • Lime: Lime binders act as a bonding agent. This is a standard component in mortar and plaster construction, and has been in use for this purpose for centuries. The mixture consists of either hydraulic lime or hydrated lime.

The process of creating hempcrete is simple and straightforward:

  • Industrial hemp is harvested and kept in a storage room.
  • The lime is kept in a silo.
  • When it’s time to create the hempcrete, the lime and hemp are mixed with water.
  • Next, the mixture is shaped into blocks.
  • The blocks are sent to a separate room for curing.
  • After curing, the blocks are loaded onto pallets.
  • The final step is to package and transport the blocks to the construction site.

Hemp Uses & Benefits In Construction

Hemp has many uses as a building material and offers many benefits as well.

Using Hemp as a Building Material

Hempcrete is quickly becoming a popular option for building materials for non-load bearing applications. Hemp has many uses for residential and commercial construction, including:

Hempcrete Homes

The biggest hurdle to constructing homes with hempcrete was legalization. Now that industrial hemp can be grown and cultivated in more places, hempcrete is quickly being adopted by the construction industry to build homes.

Hempcrete’s eco-friendliness makes it an exciting option for residential construction.

The very first hempcrete house in the U.S. was built for former Asheville, NC mayor Russ Martin and his wife Karon Korp. The home sits at an elevation of 3,500 feet and spans 3,000 square feet. The couple says the hemp’s insulating factor was effective, even at such a high elevation. Their electric bill was below-average, and they claim that they were less prone to allergies while living in the home.

Hempcrete can be used to construct many different types of homes, including:

  • Roundhouses
  • Tiny houses
  • Tiny duplexes and row houses
  • Outhouses
  • Green houses
  • Passive houses

While hempcrete does have its limitations in residential construction (it can’t be used for foundations), it’s an excellent material to incorporate into home building.

Hemp Blocks

Hemp blocks can be used in double masonry to help create natural, insulating envelopes for structures. They’re used to envelope concrete or other load-bearing masonry. Hemp blocks can guarantee consistent insulation performance, offer great support and are easier to use because of their light weight.

Hemp Insulation

Eco-friendly and often offered in batts, hemp insulation is made from 92% hemp and the remaining made of polyester fibers. Compared to other composite material, this material is far more eco-friendly and doesn’t contain the high level of chemicals or plastics that other insulation contains.

The material is compressible and often comes in a thickness range of 3.5” to 5.5”.

As an alternative to foam or fiberglass, hemp insulation has a lower impact on the environment and is easier to manufacture. Even when discarded, the material offers significant benefits because it’s a natural plant product.

The use of hemp insulation really picked up steam in 2018 and is a new alternative that builders are considering when designing eco-friendly homes.

In terms of performance, hemp insulation can be purchased in thicker varieties that add shock absorption qualities, too.

R-value will be dependent on the insulation and the studs. It’s possible to achieve an R-value of 19.25 under the right conditions which is even higher than the requirements in the coldest zones in the United States.

Other Hemp Concrete Products

Hempcrete has been used since the 90s in France and has found multiple uses in the construction industry. From buildings to structures and homes, hempcrete has multiple applications that include:

  • Walls
  • Floors
  • Roofs
  • Infill panels
  • Seating
  • Tables
  • Roads

Hempcrete is not used to build foundations, but the list of applications continues to grow in popularity.

When used for roads, hempcrete has shown effectiveness in being able to provide sound insulation. As an effective noise barrier, hempcrete can provide a practical, eco-friendly means of lowering noise pollution especially on highways.

6 Key Benefits of Hempcrete

Hempcrete offers many benefits when used as a construction material. Its eco-friendliness is its main attractive feature.

#1 – Insulating

When it comes to energy efficiency, hempcrete is a great option. It has an R-value of between 2.4 and 4.8 per inch. By comparison, regular concrete only has an R-value of 0.1 to 0.2 per inch.

Hempcrete’s insulating performance depends on a number of factors, including its density, moisture level and the type of binder used.

#2 – Does Not Crack Easily

Hempcrete is low density material, and it doesn’t easily crack under movement. It’s a great option for areas that are prone to earthquakes.

Hempcrete is also a popular option for retrofitting historic buildings. It’s often used to replace the infill panels of timber frame buildings. It can also be used to help improve insulation in old concrete structures.

#3 – Fire- and Mold-Resistant

Hempcrete is both fire- and mold-resistant, making it an excellent option for any home, outbuilding or other structure.

Because the material is breathable, moisture is allowed to evaporate, so there’s no chance for mold to growth.

Additionally, hempcrete is also resistant to pests, such as termites. This makes it a great option for homeowners because it offers easy maintenance and reduces the risk of costly repairs. Mold and termite damage alone can be astronomical if it’s severe.

#4 – Sustainable and Environmentally Friendly

Hemp is a sustainable and renewable material. The plant’s fiber is ready for harvest in two to four months. Trees, on the other hand, take years to reach maturity.

As a crop, hemp also acts as a purifier. It captures carbon dioxide even more effectively than trees. Growing one ton of hemp removes 1.62 tons of carbon from the air.

One other great benefit of hemp is that it doesn’t require any herbicides or pesticides to grow.

Hemp’s stem and leaves are loaded with essential nutrients that help feed the soil when leaves fall and decompose. Once harvested, the remnants can be returned to the soil to nourish it.

Plus, the roots of the plant grow so deep into the soil (up to nine feet), which helps prevent soil erosion. Such a deep root network helps keep the soil together.

Hempcrete also acts as a carbon sink.

Compared to a traditional brick building of the same size, hempcrete has up to a 40% lower carbon footprint.

Still not convinced that hemp is an environmentally friendly plant?

  • Hemp naturally irrigates itself, so it requires little water to grow.
  • Hemp plants absorb toxic metals and toxins from the air.
  • Hemp can grow up to three feet tall, so it makes an excellent habitat for wildlife.

Hemp is so effective at removing toxins from the air, it was famously planted at Chernobyl to remove cesium and strontium.

When building a home with hemp, approximately 2.5 acres of hemp is required for a home that’s 1,250 square feet. It only takes a few months for the crop to be ready for harvest, so a large hemp farm could potentially support a large building operation.

#5 – Long-Lasting

Hempcrete can have a lifespan of up to 100 years with proper care and maintenance. The cost is also similar to regular concrete, making it a viable alternative to conventional concrete for infill walls.

For the most part, hempcrete is comparable to concrete in terms of lifespan.

#6 – Non-Toxic

Once cured, hempcrete does not emit any harmful byproducts. This bio-composite material is considered generally safe, although fertilizers may be used to grow industrial hemp.

The non-toxic nature of hempcrete makes it a great option for promoting healthy indoor air quality. Many hemp home owners state that they have less problems with allergies compared to traditional homes.

Is Hempcrete the Future of Green Building?

Hempcrete’s environmental-friendliness and sustainability make it a great option for green construction. It cannot fully replace traditional concrete, but it can be used alongside it to improve insulation while reducing your carbon footprint.

Now that industrial hemp is legal to grow and cultivate, hempcrete will likely make more of an appearance in the construction industry. The insulating nature of the material combined with its light weight and sustainability make it a valuable addition to the green building industry.

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Markella Menikou – Paniotis Concrete House