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What Is Hempcrete?

Hempcrete blocks painted blue with a red door and blue garage door.

Hempcrete is a promising sustainable building material made from everybody's favorite eco-friendly superstar: hemp. But if you haven’t heard of hempcrete yet, you aren’t alone! Even if you love sprinkling hemp hearts on your smoothie bowls or lounging at home in your comfy hemp bra and boy shorts underwear, this material-of-the-future is still rather unheard of.

But ya know what? I think it's high-time more people know that hemp isn’t only one of the world's most sustainable fabrics—it's a force to be reckoned with as a building material, too! That's right, I'll say it: hempcrete is truly poised to change the industry—and the world—for the better. How does lowering the global use of pesticides and trapping carbon better than trees sound?

Hempcrete does this, and more. Prepare to be impressed as you learn what hempcrete is and all the ways it can be used!


HOW IS HEMPCRETE MADE?

Hempcrete is made from just three simple, natural ingredients: hemp, lime, and water. But before asking “How is hempcrete made?” we need to ask what part of the hempcrete plant is used to make it! That’s the truly amazing part.

Two hands in gloves hold cannabis leaves.

Unlike other hemp products (like the kind you eat or wear) hempcrete is made with the inner core of hemp plants. This part is known as the “hurd,” “shiv,” or “shive”. It’s this part that remains after the hemp fiber has been stripped away from the outer stalk for other purposes, like making some hemp thong underwear.

On its own, this leftover inner stalk material can be shredded and used for pet bedding or compressed into fuel pellets, but these are far from its most impressive uses.

This remaining core happens to have a high silica content that naturally binds well with the mineral lime. Hempcrete is made by chopping up the woody hurd and combining it with lime and water. When this happens, a chemical reaction takes place between the water and lime that fuses the hemp hurd pieces together. Once this compound dries, the result is hempcrete, a bio-composite that looks like cement. Instead of being discarded, the valuable core of the hemp plants can be used to help build houses!

White hempcrete blocks in a white wall.

CAN HEMPCRETE BE USED LIKE CEMENT?

Hempcrete can’t be used exactly like cement. That’s because while it may look like cement, hempcrete behaves much differently. (And this is a good thing!) For one, hempcrete weighs seven to eight times less than cement. Hempcrete blocks can even float in water!

Hempcrete is so much lighter than cement because the lime and water binder only bind the hurd together, they don’t fill all the empty spaces between the pieces. Unlike cement, fully mixed hempcrete contains a large number of small air-filled voids that weigh nothing. And these are what help reduce the overall weight of the product and lead to its buoyancy.

Given its light weight and airiness, hempcrete doesn’t have the same load-bearing abilities and can’t be used in all the same ways as cement. This difference, however, doesn’t mean hempcrete is worse than cement. Some of what makes it different also gives it distinct advantages! For instance, unlike cement, hempcrete’s light weight makes it super easy to transport and build without heavy-duty machinery. Ya gotta love that!

Hempcrete blocks and panels being used as insulation between joists and wall framing.

HOW CAN HEMPCRETE BLOCKS AND PANELS BE USED?

Hempcrete blocks and panels have many uses, but unlike cement, they’re not good materials for foundations. This bio-composite needs to breathe, so all uses must be above ground. Here are just a few ways you can use hempcrete blocks and panels in construction:

  • To build non-weight bearing walls
  • In flooring
  • As roof insulation
  • As wall insulation

One great benefit of using hempcrete as insulation? It can lend some structural support to a building, ensuring that wooden joists and support beams don’t sag or bend. On top of that, using hempcrete for walls saves time because plaster can be applied directly to the hempcrete on interiors, without any drywall, mesh, or additional bonding agents. Plasterboard can be affixed to hempcrete with screws.

A man builds a wooden structure while sitting on top of it

Once complete, hempcrete can be painted with lime-based paints or covered in timber cladding on either the exterior or interior. These choices work because they’re both super breathable, which is essential when using hempcrete. No vinyl siding required here! All this means that hempcrete makes a great choice for those who want to build in the most natural and sustainable way possible.


IS HEMPCRETE A NEW INVENTION?

Hempcrete isn’t a new invention. It’s a rediscovered invention! The history of its use is fascinating. In the 1980s, hempcrete was discovered in some Merovingian bridges in France built way back during the 6th century. Talk about withstanding the test of time. 1,500 years is pretty impressive.

An old stone bridge and castle sit in a bright green field.

But even long before that, hemp hurds were mixed with lime and oil to make caulk for Chinese junk ships as far back as 200 BCE! It turns out that the fantastic qualities of the hemp plant core were discovered a long, long time ago. But not in a galaxy far, far away. Right here on earth.

Today France is the biggest producer of hemp in Europe. Hempcrete was first used (again) in France in the 1990s in non-weight-bearing walls. Since then, it’s seen increased use in construction there but seems poised to grow even more.

By some accounts, only 5% of the hemp hurd harvested in France is currently used to make hempcrete. So, it’s probably an understatement to say that there is a lot more of this valuable material available to be used.

WHAT ARE THE BENEFITS OF USING HEMPCRETE IN CONSTRUCTION?

The benefits of using hempcrete in home construction are financial, practical, and cool —in more ways than one.

A blueprint for a new home with a tape measure and pen.

In the United States, the first hempcrete house was built in 1990 in Asheville, North Carolina. Russ Martin and Karon Karp wanted to construct a healthy home in an environmentally friendly way. Their architect suggested using hempcrete.

There are sooo many benefits to owners using hempcrete in their home’s construction:

  • Lower heating and cooling bills due to excellent insulation
  • Few allergy symptoms due to mold and mildew resistance
  • Better indoor air quality due to non-toxicity
  • Savings on homeowner’s insurance due to fire-resistant properties
  • Peace of mind that hempcrete can be used as fertilizer instead of going to a landfill
  • A cool looking house that uses sustainable and natural material!

If I met Russ and Karon or other owners of hempcrete homes, I’d also like to ask them if they enjoyed hempcrete’s excellent acoustic absorption. Did their music sound better there? (And would it do anything to improve my singing voice?)


4 REASONS HEMPCRETE IS THE BUILDING MATERIAL OF THE FUTURE

A green field of hemp plants near mountains.

1. HEMPCRETE IS A RENEWABLE RESOURCE

Compared to other agriculture crops, hemp crops have exceptionally high yields per acre. The U.S. Department of Agriculture found that worldwide yields range between 2.5 to 8.7 tons per acre. (By comparison, typical yields for wheat range from only 1.25 to 2.5 tons per acre.)

No other crop provides as much available biomass by volume from a single crop as hemp!

Also, unlike many other crops, hemp grows so densely that it prevents the growth of weeds. When it’s grown in rotation with other crops, herbicides aren’t needed for the following crop because the hemp crop has prevented the weeds from taking root in the soil, leaving behind only healthy soil to support the next crop. You could say that hemp leaves the earth better than it found it.

A sky full of clouds overlaid with an image of greenhouse gases being emitted by factories.

2. HEMPCRETE HAS A LOW ENVIRONMENTAL IMPACT

Hempcrete’s primary ingredient is sourced from a natural by-product of other hemp products, including hemp seed oil and men's boxers, and its three simple ingredients are entirely natural.

Hemp farming requires much smaller amounts of pesticides and herbicides than other crops (since it squeezes those pesky weeds out of space). While it does require fertilization, its harvesting and processing also don’t need extra heat or any chemicals.

Additionally, hemp plants have the incredible benefit of sequestering carbon dioxide, making them a carbon-negative material. According to one study, over 700 pounds of carbon dioxide are sequestered in each ton of dried hemp. In another study, finished hempcrete was found to sequester 307.26 kg (677.39 lbs) of carbon dioxide per cubic meter (35.31 cubic feet).

I know it might sound confusing, but this translates to 8.7 pounds of carbon dioxide sequestered in each cubic foot of hempcrete. That’s pretty impressive, if you ask me! In fact what that means is that among carbon-negative building materials, hempcrete is the best performer of them all.

Green hemp leaves growing.

If you’re keeping track, this means that hemp is #1 in yield by acre AND #1 in carbon sequestration!

No matter what use they’re grown for, all hemp plants absorb carbon dioxide from the atmosphere while they are growing. But it doesn’t stop there. Finished hempcrete continues to absorb carbon dioxide over time. There aren’t many building materials that can claim to reduce carbon dioxide levels for years to come! I told ya you’d be impressed.

And since keeping garbage out of the landfill is essential for a healthy environment, this is yet another way that hempcrete completely rocks. It leaves no waste behind and never needs to go into a landfill. If there is leftover hempcrete after a project, it can simply be tilled into the surrounding earth. The hemp hurd and lime will just combine with the soil and break down.

3. HEMPCRETE BLOCKS ARE BETTER BUILDING MATERIAL FOR A WETTER WORLD

A house made with hempcrete in a snowy field surrounded by trees.

Unlike many building materials, including drywall and wood, hempcrete can store a lot of moisture without growing mold. Hempcrete’s lime binder is naturally antimicrobial and antifungal, and that’s what makes it highly resistant to mildew.

Hempcrete’s natural mold resistance makes it an excellent building material to use in humid or wet locations, in either hot or cold climates. Hempcrete handles extra moisture in the air in two ways. On its exterior, hempcrete adsorbs water. This means it holds it in a thin film on all its surfaces. Secondly, hempcrete also absorbs extra moisture into its cellular structure.

Together these features allow hempcrete to carry extra moisture in the atmosphere and then release it when conditions dry out -- without growing mold.

4. HEMPCRETE CAN REPLACE UNHEALTHY INSULATION

Conventional pink insulation being placed inside a wall.

For insulation purposes, hempcrete is a better choice than conventional insulation sold in rolls or blown into spaces. These kinds of insulation often contain ingredients that can pose health risks, including formaldehyde, toxic chemical flame retardants, or volatile organic compounds (VOCs). Hempcrete has none of those!

Along with increased precipitation in some areas, global warming is also causing more extreme temperatures in parts of the world. Some places are getting hotter while others are dealing with more extreme cold.

To deal with these extremes, builders will need to utilize insulation to help regulate indoor temperatures for their inhabitants. The demand for effective insulation will increase. Hempcrete can help address this issue. Its increased use in buildings as insulation can help keep people feeling comfortable while preventing exorbitant energy costs for heating and cooling. Feeling comfy and saving money sounds good, doesn’t it?

A new house constructed using hempcrete insulation.


SPECIAL CONSIDERATIONS WHEN USING HEMPCRETE

At this point, if you’re anything like me, you’re probably convinced that hempcrete is pretty incredible. You might even be wondering if you can make some yourself.

But not so fast. Hempcrete must be mixed very carefully. And it’s best left to the professionals.

Powdered lime can burn the skin and create a lot of caustic dust. For this reason, face masks, gloves, and skin coverings must be worn by all involved in the mixing process of hempcrete. Fortunately, once it’s mixed and dried, this is no longer a concern. Finished hempcrete gives off no gases or scents.

While hempcrete has a short ingredient list, the ratio of those ingredients is also very delicate. Even small changes can affect the hempcrete’s strength and breathability. It's not like whipping up a batch of your favorite brownies—standards must be maintained for safety and reliability, especially when hempcrete blocks are intended to build walls or included in roofs and floors.


WHERE TO BUY HEMPCRETE?

The easiest way to get your hands on hempcrete, then? Check out one of these popular sellers! Choose between buying a pallet of powdered hempcrete to mix yourself, pre-made blocks, and even hemp add-ons like eco-friendly binder and hemp insulation!

  • American Hemp LLC: buy their hempcrete in single bags, a whole pallet, or even a full truckload for those big building projects!
  • DTE Materials: this brand sources their hempcrete from leftover CBD stalks, eliminating unecessary waste from the hemp manufacturing process. This also makes their hempcrete more affordable than other options!
  • Hemp Block USA: while you can't use hempcrete for building a foundation, Hemp Block USA makes unique interlocking and loadbearing blocks you can purshase premade. Score!
  • UK Hempcrete: shopping on the other side of the pond? UK Hempcrete offers a variety of hempcrete products, as well as other eco-friendly building materials to take you all the way from start to finish!


THE FUTURE OF HEMPCRETE IN CONSTRUCTION

A large white and wood modern home with lights on from the outside.

How is hempcrete made and what can it be used for? Now that you know you’ll probably agree that the modern-day uses of hempcrete have only just begun to be explored.

Environmentally-friendly hemp is expected to become a $41.78 billion industry by 2027. Just think of all that hemp hurd in the cores of those plants, so full of potential for builders! And your choice to wear hemp hipster panties could even fuel its growth even more.

Already in places as diverse as Massachusetts and Florida, builders are advertising their use of the material. Hopefully, as more hemp is grown in the US and Canada, its use in North America will spread even further. Would you like to live in a house made with hempcrete? What benefit do you think you’d enjoy most? Let me know in the comments!




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