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I've already explored tiny homes, Earthships, passive homes, and also modular homes as more
efficient and sustainable alternatives to traditional houses. But what if you could
build a home or apartment building that's not only fire-resistant like concrete but
also more efficient and sustainable than conventional homes? Let's explore hemp building materials
and their benefits for achieving a low-carbon future. Could hemp blocks be better than concrete?
I'm Matt Ferrell. Welcome to Undecided.
Alongside renewable energy and EVs, sustainable homes are crucial for driving our world towards
a net-zero future. On a global scale, residential homes and apartments account for about 21%
of carbon emissions, where heating and cooling make up a big piece of that pie. However,
the manufacturing and building process, as well as traditional construction materials
like concrete and metals, generate carbon emissions and waste.
Concrete is the most used building material around the world and contributes about 8%
to the world’s CO2 emissions. Steel contributes an additional 11% to global carbon emissions.
In order to build more sustainable homes, and map a pathway to a net-zero future, natural
and eco-friendly building materials are being developed. A few examples are straw bales,
rammed earth, recycled plastic, bamboo, mycelium --- which I covered in a previous video --- and
many more. However, there's an eco-building material that a lot of you have been commenting
about in my other videos and has also been gaining attention around the globe. Due to
its resilience, insulating properties, fire resistance, low carbon footprint, and its
lower density, the next eco-building material may be Hemp!
When someone brings up hemp, your mind might jump straight to marijuana. It’s 4:20 somewhere.
Hemp is a variety of *Cannabis Sativa* that only has a very small portion of THC, which
is the substance that causes psychoactive effects. I’m sure some of you are well aware
of that. Marijuana flowers can contain 15% THC on average, and when extracted, that level
can reach up to 90%. For some reason I’m suddenly getting the munchies. Hemp however
only has about 0.3%. It’s a very versatile product that can be used for clothing, producing
seeds for oil and eating, ropes, food, and more. Even so, it’s had a bit of a turbulent
history.
Hemp has been harvested for thousands of years, with evidence of its use going back to 8000
BC in Asia. Around 600-200 BC, hemp was used by Europeans to make ropes. By 100 BC, the
Chinese started to make paper out of the plant. In the1600s, Americans had discovered the
benefits of using hemp for making food, ropes, shoes, and clothes.
After the repeal of the prohibition of alcohol in 1929, marijuana was pointed to as a 'devil
drug.' Even though hemp had nothing to do with marijuana, it was caught up in the early
war on drugs. In 1937, the US approved the Marihuana Tax Act, charging cannabis dealers
and making cannabis illegal. While hemp was still technically legal, the requirements
around importing and exporting hemp made commercial production in the US less economical.
In 1971, after years of its forbidden use, the UK began issuing hemp licenses for farming,
provided hemp was grown for non-drug purposes. The United States began to issue licenses
in 2007. It took until 2018, with the passage of the US Farm Bill, that the US government
defined industrial hemp as a federally legal plant, as long as it doesn't contain more
than 0.3% THC.
All of that legal drama held back any further research or development into hemp for practical
use in the UK and the US., In France, however, there was a push to find a suitable alternative
for rotting wattle and daub in medieval timber-framed houses, and hemp had some real advantages.
Since then, making building materials out of hemp has been spreading worldwide as a
more sustainable alternative to traditional building materials. Perhaps one of the most
investigated products is hempcrete, which has some similar properties to concrete.
But before getting to the pros … and cons of hempcrete, I'd like to thank today's sponsor,
CuriosityStream. If you'd like to watch more videos on topics just like this, you really
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an incredible deal. Link is in the description below and thanks to CuriosityStream, and to
all of you, for supporting the channel. So back to what hempcrete is and how its building
up…
Hempcrete is a composite made by combining water, lime and hemp stalks' inner core. The
lime component is made up of air lime, which is designed to accelerate the setting process.
This combination results in a flame-resistant, pest resistant, moisture-balancing and strong,
biodegradable insulator. In addition, hempcrete is also reusable if milled and rehydrated.
Hempcrete is suitable for constructing self-insulating walls, roofs, and screeds, and it's adaptable
to either new construction or renovations. Typically, hempcrete is cast around a structural
frame made of wood, metal, or concrete when building walls. It can be used to repair damaged
cob walls in half-timbered walls.
While these are nice capabilities, when we’re talking about sustainable homes, one of the
biggest things to look at is insulation value … or the difficulty for heat to pass through
it.. That’s where hemp takes a commanding lead. Homes built with hempcrete can achieve
fantastic thermal performance. While concrete has thermal insulation from 0.62 to 3.3 W/mK
(Watts per meter-Kelvin), hempcrete’s value ranges from 0.06 to 0.07 W/mK --- the lower,
the better. A lower value means less heat can pass through the hempcrete than concrete,
keeping a house warmer in the winter and cooler in the summer.
You might be more familiar with R-value, which is basically the material's resistance to
conduct heat --- the higher the R-value, the greater the insulating effectiveness. For
concrete used in floor slabs, for example, the R-value ranges from 0.1 to 0.2 per inch
of thickness, so a 6 inch thick slab would have an R-value between 0.6 and 1.2. On the
flip side, the R-value for hempcrete ranges from 2.4 to 4.8 per inch, so that same 6-inch
slab would have an R-value of 14.4 to 28.8. That’s kind of a crazy difference … which
means hempcrete will save money on a building's energy bill and maintenance costs over the
product's entire lifespan. For a quick cost comparison, concrete is cheaper than hempcrete,
costing $85 per square meter, while hempcrete, on average, costs $135 per square meter. But
hempcrete can provide from 50% to 80% in energy savings, mainly with heating and cooling.
For a real world example, a 170m² home built by DB Chanvre utilizing hempcrete and a timber
frame system combined with an insulating wall, ground floor slab and first floor screed,
had a heating bill of €300 (about $340) for six to seven months of heating --- which
can vary depending on the year. For comparison, the heating bill for a similar sized house
would be about $1,055.
But wait, there’s more! Both concrete and hempcrete do something that’s important
to factor in: they both absorb CO2 during their life. They’re both carbon sponges,
but concrete doesn’t offset the negatives of producing it. In 2018, each ton of concrete
produced released between 0.5 and 0.6 tons of CO2, but according to an Intergovernmental
Panel on Climate Change (IPCC) report, concrete absorbs about half of that CO2 during its
life. On the other hand, hemp is carbon-negative, sequestrating more CO2 from the atmosphere
than is emitted during its production. One hectare of industrial hemp can take 15 tons
of CO2 from the atmosphere.
And the lifespan of hemp as a building material can last for centuries depending on the weather
conditions. In Japan, for example, a hemp house built in 1698 -- more than 300 years
ago -- is recognized as a national heritage site.
How does hempcrete stack up against concrete when it comes to strength and costs? Concrete
is non-toxic when cured, fire-resistant, pest-resistant, can last for thousands of years and tolerates
standing water better than hempcrete. However, a cubic meter of hempcrete can hold more than
1,300 pounds of water vapor without degrading, performing very well even in high-humidity
conditions. When it's raining, it can absorb the water and release it when the sun comes
out again, protecting the building from moisture and not cracking like concrete does over time.
When it comes to compressive strength, which is basically the resistance of a material
to crushing before breaking, concrete can easily achieve compressive strengths ranging
from 3,000 psi to 4,000 psi. On the flip side, hempcrete reaches much lower levels from 72.5
psi to 507.6 psi, but that can be addressed with additional supporting frameworks.. However,
compressive strength isn’t the only measure of strength. Hempcrete is three times more
resistant to cracking than regular concrete during an earthquake where shear loading (trying
to tear) becomes more important.
Although hempcrete is exceptionally lightweight and has excellent insulation properties, it’s
not as capable of being a load-bearing wall by itself. You can't build a house's foundation
with hempcrete on its own. Materials like wood or steel still need to be used to create
the basic structure, in addition to traditional plumbing and electrical materials. Although
hempcrete has some cons, there are some newer hemp products that can make up for that.
A few companies are producing hemp blocks, which are basically hempcrete-like blocks
that are dry glued or interlocked. They can be used as formwork and filler for a strengthened
concrete column or beam structures, so it can be used in load-bearing walls and in-fill
walls. Just like hempcrete they don't have load-bearing capacities on their own, but
the integrated framework takes on that role.
Just Biofiber Structural Solutions, a Canadian company, has developed a system with a composite
structural frame inside each block that interlocks when stacked. That structural frame is what
gives it the load bearing capacity. It’s like a giant LEGO block, but one that weighs
about 13 kg (28.7 lbs) per block. I don’t think you’ll be getting this for your kids.
They have great air and humidity permeability, can resist fire for two hours, and have a
life expectancy of 100 years.
When it comes to embodied energy and carbon sequestering, each block can take 6.5 kg of
CO2, which means sequestering an average of 10 tons of CO2 per home. On the construction
side, the interlocking LEGO style system reduces time for construction, which means saving
on labor costs. The estimate is about $32/sqft per working hour.
One of their first projects, the Harmless Home, is a net-zero home in Victoria, British
Columbia. This sustainable house is taking advantage of the high insulation capacity,
along with rainwater harvesting, filters for potable water, a wastewater treatment plant
that creates clean water, and more.
Another company that’s been developing a similar idea is HempBLOCK, which operates
in Australia and the US. Their product can be used for external and internal insulation,
partitions, renovations, and can be used in load-bearing walls and in-fill walls. Their
products can save up to 70% on heating and cooling bills, as well as reduce construction
time by up to 80%. When it comes to costs, a HempBLOCK is about $20.
According to Johan Tijssen, Director of HempBLOCK USA and Australia, at $14 per square foot,
using HempBLOCKs to build house walls is cost-competitive or even cheaper than utilizing conventional
building materials. The price of concrete walls varies according to the thickness and
location, but Home Advisor states that the cost per square foot ranges from $10 to $60.
Even with these advantages, there are a few challenges that need to be overcome in order
to make it a mainstream sustainable building material. Hemp fibers are usually ready to
be harvested in two months, but there's also a period for curing, so it's not as instantly
available as concrete. Also, there aren't many builders with hands-on experience in
building homes with hempcrete, as well as a lack of information and education around
it.
Despite that, it's inarguable that hemp has several properties that are great for building
sustainable homes. There’s even more I could go into like hemp wool insulation or hemp
flooring, but that’s out of scope for this video. It’s an incredibly versatile product.
The global industrial hemp market was valued at $3.61 billion in 2020 and is expected to
expand at an annual growth rate of 16.2% from 2021 to 2028. Although hempcrete can't totally
replace concrete for all applications, there are several benefits to using hemp for building
sustainable homes. It can provide a healthier environment for homeowners, not to mention
the savings with heating and cooling, and help build a more sustainable world. Although
building a home with hempcrete and hemp insulation is currently more expensive than using concrete
and traditional materials, the savings in electricity from the incredible insulation
values can offset the upfront cost. In addition, with more companies jumping into this market,
prices should lower in the coming years. Hempcrete products may not be the silver bullet to kill
off our needs for concrete, but it’s a very capable product that can fill a lot of different
use cases.
What do you think of using hemp in construction like this? What about other uses of hemp?
Jump in the comments and let me know. And if you have knowledge on this, or work in
the industry, please share your experience so we can learn more together. You can also
join my Discord server and talk to other members of the community. The link is in the description.
And thanks as always to my patrons and a big welcome to new Producer Ty Wang and Supporter+
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