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Modern Day Uses of Hempcrete

The History of Hemp

With the Founding Fathers drafting the Constitution directly on hemp paper, it’s apparent that the utilization of industrial hemp isn’t new. In fact, using the hemp stalk’s fibers for building materials and other industrial uses has been around for tens of thousands of years, and it doesn’t show any sign of slowing now.

If one of the US’ most important and longest withstanding documents was crafted from hemp fibers, that leaves us wondering: just how far back do hemp’s industrial uses really stem?

In the Beginning

 We are able to trace back some of the first uses of hemp to 8000 BCE all across Asia. Though hemp was traditionally utilized for foods, archeologists have been able to find traces of hemp cord in ancient pottery and textiles, suggesting that these communities had been utilizing the plant for years.

Not too long after this, people began to realize the potential that hemp had towards other industrial uses. Thus, hemp paper, clothes, and ropes were born from the stalks of the precious plant. Over the next decades, we see the utilization of these fibers spread to Britain, the Middle East, and even the Vikings in Iceland.

It wasn’t until the early 1600s that hemp was brought to North America for Westerners to enjoy. They hopped on the bandwagon of crafting rope and paper with hemp, and also chose to make things like lamp fuels using hemp oil from the seeds of the plant.

The 20th Century and Now

 Throughout the early 1900s, hemp was still widely popularized, despite a tax being placed on it in 1937. This tax was meant to discourage people from growing hemp, but instead, we saw people like Henry Ford crafting an experimental “hemp car,” with the body being made from hemp fibers instead of steel.

Then, less than 30 years after Ford’s experiment, the US classifies hemp as a Schedule I drug, almost seemingly erasing the versatile benefits the plant brought throughout the country for decades.

Though acceptance of hemp slowly began to regain traction during the 2000s, it wasn’t until 2018 when we saw the passing of the 2018 Farm Bill, which legalized the cultivation of the plant for farmers who follow strict regulation.

Today, hemp’s popularity is close to what it was decades ago, and for great reason. With advancements in technology and materials, we’re now able to fully realize the hemp fiber’s potential, especially as a building material. With houses, buildings, and even major structures being made out of industrial hemp, there’s no doubt we will surely see a future that involves this powerful plant.

The Rise of Hemp Structures

 When we think of the hemp plant, our minds usually don’t think of commercial buildings, homes, and other structures. But in reality, we really should be. The hemp plant has been used for industrial uses for thousands of years, with the stalk’s fibers being strong enough to build cars and bridges. It may sound impossible, but the hemp stalk’s fibers are some of the strongest materials on the planet, and because of it, we’ve been turning to it as an alternative building material for structures for decades.

 As the years progress and we are beginning to learn more about hemp and its industrial uses, we’re also able to recognize some of the earliest creations made of hemp or hemp mortar. In fact, we’ve discovered bridge abutments in France that were built in the 6th century using hemp mortar. Proving reliability and durability, these abutments are still standing today.

Actually, France has continued to use hemp within their building materials, reviving the practice back in the late 1980s. Utilized for the renovation of the Maison de la Turquie, a hemp-based concrete proved to be an ethical, sturdy alternative to traditional concrete. This was one of the world’s first uses of hempcrete, and it has only gained popularity across the globe since.

Benefits of Building with Hemp

What Is Hempcrete?

Hempcrete is a mixture of hemp hurds (also known as “shivs,” the woody inner core of the stalk), lime binder, and water. In some cases, it may include natural hydraulic lime, pozzolans or sand.

The term “hempcrete” to explain the material came about because it is meant to imply a greener building alternative to concrete.  While this is not the best comparison because hempcrete is not load bearing, the term still carries merit simply because of the carbon emissions that comes from building with concrete compared to the carbon sequestered building with hempcrete. In some circles, it is simply called “hemp lime.”

More About Hurd

The two types of fiber found in hemp are its hurd and bast fiber. Because of its high cellulose, hemp hurds are great for absorption. It can trap pockets of air as well as retain or release moisture. As a result, hemp hurds act as a crucial component to hempcrete’s incredible insulation and ventilation properties. And to think that there was once a time when these hurds were considered a waste product.

What are the Benefits?

Perhaps hempcrete’s greatest gift to give the world is what it takes away. It is carbon negative and helps reduce our carbon footprint.  For every cubic foot of a hempcrete wall, about 7-10 lbs of carbon is absorbed and locked.

Hempcrete also offers amazing insulation properties which can be confirmed by its U-Value and R-Value. U-Value is a measure that refers to the heat transmission through a building part or material and is meant to describe thermal performance. The lower the number, the better for insulation. Depending on the thickness of the wall and other variables, hempcrete’s U-Value can range from 0.16 to 0.52 W/m²K.

R-Value refers to just how well a specific building material can insulate (its resistance to heat transfer). The higher the R-Value, the better the insulation. The better the insulation, the more energy (and thus money) to be saved.  Hempcrete’s R-Value will vary depending on wall thickness and other variables, but it has been reported to range between  2.4 – 4.0 per inch.

Depending on the application (floor, roof, walls), hempcrete insulation can offer additional benefits for the home, including sound insulation.

Here are some other benefits:

  1. It is waterproof, recyclable, non-toxic and biodegradable. It can be used as a fertilizer once demolished.
  2. It is vapor permeable and can mold to uneven walls, making it a great replacement of infill panels when retrofitting buildings
  3. It is fireproof and mold resistant.

Does it have drawbacks?

Some. The material is non-load bearing and it takes weeks (and in some cases months) before it’s fully cured and ready for application.

Modern Day Hemp Builds

 Today, hempcrete, hemp rope, and other hemp-based building materials are becoming preferential during construction projects. Hemp provides various benefits that traditional building materials don’t; hempcrete, in particular, is mold-resistant, fire resistant, and waterproof. Let’s be honest: that isn’t something we can say about most industrial materials.

Not only are these materials being used for commercial buildings and structures, but we’re using it for homes, too. The first house in the US to be constructed using industrial hemp was built in 2010 in North Carolina, though European countries had been using it for decades prior. Since the home in North Carolina was constructed, dozens have followed suit, with people across the country realizing every day the benefits that industrial hemp can bring.

Eric McKee’s Wnder Wrkshop in the state of Colorado

Eric Mckee of the US Hemp Building Association started from very humble beginnings. “For years I had been wanting a small workshop/studio to work on my projects. As an industrial designer I am always intrigued with new green methods and materials. Once I was introduced to hempcrete and its attributes, I realized there was no other option,” McKee says. In starting the project, many of his neighbors and community have come around to understanding his advocacy with many embracing and even offering Mckee assistance in advocating for greener building methods.

As for his latest and greatest structure, he says “its currently less workshop and more of a home office. It’s also a great place for the kids. We tend to make a mess doing crafts and our 3-D printing projects. I also use it as a sales tool when I have clients come visit and for educating when having workshops here at the house — it’s also the mailing address for the US Hemp Building Association.”

Cameron McIntosh, founder of Americhanvre and Director at Large of the US Hemp Building Association, Drew Oberholtzer and Ana Konopitskaya of Coexist Build, decided to take a hempcrete build on the road. “This Hemp House On Wheels (Hemp HOW) was built to showcase the applications of hemp and its adaptability to modern design and pressing sustainability issues; it was designed and built without petroleum- based products.

The walls of Hemp HOW are constructed of hempcrete, or hemplime, – a non-structural bio-composite insulation material that is cast in place around traditional wood framing.  It is comprised of hemp hurds (the woody inner core of the hemp stalk), lime-based binder, and water.  These simple materials come together to form a product that is mold, mildew, rot, pest and fire resistant.  Hempcrete is typically finished, as it has been here, with a three coat, traditional lime based plaster system on the inside and out.  This finish allows the hempcrete to “breathe”, passing water vapor freely through the wall system as the lime interacts with varying humidity levels.  It is due to this action that hempcrete is able to regulate humidity in a built environment, and why it is touted as a dynamic thermal and acoustic insulation.  This system replaces the siding, house wrap, plywood sheathing, insulation and drywall in traditional American home construction.  It is hempcrete’s compatibility with other materials and its versatility and performance that set it apart from other well known sustainable building methods.  Our floor has been sealed with Hempshield, a hemp-oil based natural sealer for wood floors and decking.

The acoustical ceiling tile, designed by Coexist, is made of hemp hurds and mushroom mycelium, and was produced by Ecovative out of Green Island, NY.” McIntosh explained.

Hempcrete House on Wheels done by Americhanvre and Coexist Build

We also asked McIntosh what the challenges were of building a hempcrete house on a trailer. “The most challenging aspect, of which there were many, of building the Hemp House on Wheels was the timeline.  Everything but the basic frame of the trailer was custom built, which meant great pain and time invested in designing and building the unit.   We had been invited by the National Hemp Association to participate in the CWCB expo at the Javits center in New York, and this was an opportunity we were not going to miss.  The entire sequence for the build was based on that timeline and it still came down to the wire.  We had a last-minute paint change, along with damaging winds and hail, about two days before the show.  Those setbacks and a delivery window that was moved up by eight hours made it so that we had about six hours of sleep in the three days leading up to the event.  All of this made our delivery of the unit on time an even greater triumph!”

Matthew Mead of Hempitecture — yet another advocate for using hemp as a sustainable and versatile building material took on a large project retrofitting an existing home. “Renovations of any kind on an existing structure are always a tricky question. In regard to the renovation project I worked on, most of what I worked on was an addition off the back of the existing house. I love the idea of being able to preserve older architectural styles and materials, and if it is practical to give them new life, it’s a great way to go. Hempcrete can be used as a material for renovations, but it is more well suited for renovating masonry-based projects, due to hempcrete’s vapor permeable qualities,” Mead shares on comparing this method versus using what already exists.

With a perfect score on the ASTM test (a test that measures smoke developed and flame spread — two metrics of material reaction to fire). Mead says he built the structures for an ASTM E84 test on behalf of one of his clients. “Our hempcrete sample scored a 0 out of 450 in both categories, essentially proving that hempcrete is fireproof. This is the first test of its kind done in the US and is a key step in moving hempcrete towards acceptance in the US. There are many more tests that need to be conducted, which are being looked at independently by researchers, universities, and the US Hemp Building Association is working to spearhead a standards committee with ASTM.”

Innovative Hemp Construction Materials and Supplies

As more and more of the brightest minds in the hemp and green building industries come together and join forces, we will continue to see innovation with hemp building materials.

Earlier this year, McIntosh held a workshop where he premiered a tool that sprayed hempcrete onto a wooden frame in Pennsylvania.

McIntosh using the Baumer Ereasy spray to apply hempcrete

Those who have worked with hempcrete have been using the hand-tamping method to build their structures. We asked McIntosh more about this innovative and efficient way of applying the hempcrete binder. “We at Americhanvre have added a new capability to our tool box; the Baumer Ereasy spray applied hempcrete system invented by Damien Baumer and distributed by our colleagues at Hempitecture in Ketchum, Idaho.  This system delivers a pre-mixed hemp and lime mixture to the wall cavity about three to four times faster than traditional cast in-situ methods.  The primary benefits of this type of installation method are; a decrease in labor on site, increased uniformity of placement and accelerated drying times.  It is critical for our industry to find ways to mechanize the delivery and to compress the installation timelines of these materials such that the overall costs associated with their employment fall in line with traditional building materials.  The fabled gap between sustainability and affordability must close in order for real change to occur within the construction industry.”

Another innovative hemp material that can replace common insulation is HempWool, an alternative replacement to traditional insulation made by Hempitecture. Made from 92% industrial hemp fiber with an R-Value of R-3.7/in, it outperforms competitors that use toxic home insulation. HempWool comes in a variety of depths and widths, making for quick and easy insulation.

Final Thoughts

Cement is the second most consumed commodity in the world (only second to water) and it is one of the major producers of CO2 emissions. It is reported that 39% of the world’s carbon emissions come from building and construction.

In order to reduce this carbon footprint, more houses and buildings will need to be constructed using the hemp plant and other known eco-friendly green materials.  But it is not until hemp becomes a certified building material on a world-wide scale that we will be able to take significant steps toward reducing these emissions. As we continue to embrace the hemp plant and its versatile fibers, the more hemp-based structures we’re going to see.

However, there is reason for hope and optimism. More and more homeowners are seeking a “low impact living” lifestyle, as evidenced by the growing green construction industry.  Once these consumers learn that hemp is one of the most powerful sustainable green building materials on the planet, their voices will be too loud to ignore. So, the next time you think of hemp, don’t forget about the historic bridges and modern-day homes that stand tall because of this powerful plant.

Written by Mell Green, NHA Volunteer Writer and James Ar of Hemp & Prosper as guest contributor

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