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Hempcrete: Sustainable Building Materials For A Greener Future

Hempcrete is the ideal sustainable masonry for eco homes in Australia. Building companies are increasingly discovering its value – let's take a closer look!
lady watering a hempcrete house

Over the past decade, climate change has been hastened by a “business as usual” approach. Many of us have come to accept that sustainability and construction may never be best friends. Hold up, though – hempcrete has just taken a seat at the table. Well, actually it’s been sitting there the whole time…

Many of us are familiar with the common culprits of climate change – industry, transportation, electricity and agriculture – but what about concrete?

As global population soars, so too does demand for construction and building materials. And if we consider all stages of concrete production, it is believed to contribute up to 8% of the worlds CO2 emissions!


Enter, hempcrete.

As the name suggests – it’s an eco-friendly building material made from hemp. Think of it as the archnemesis of concrete: it is superior in almost every single way. It is safe, thermally efficient, long-lasting, non-flammable and even moderates internal humidity levels. And the best part – it is carbon negative.

More on that in a moment – first, let’s get down to the nitty gritty.

What Is Hempcrete?

Hempcrete is taking the world by storm – but what’s it all about?

Hempcrete is made from hemp “hurd” – which is the inner woody core of the cannabis plant. Producers strip the outside of the hemp stalk, leaving the woody hurd as the by-product. This is mixed together with lime and water – that’s when the magic happens. A chemical reaction occurs between the lime, water and hurd, resulting in the particles bonding together.  

Hempcrete can be used for non-bearing walls, insulation for the floor or roof, and as a finishing plaster – the perfect solution for eco homes in Australia.

Now, its time to clear one thing up: you won’t get high living in a hemp house. That would be terribly unproductive. You see, hemp is believed to contain less than 0.3% THC by dry weight (the stuff that makes you high) – which isn’t enough to give you any psychoactive effects. It is marijuana (hemp’s brother) that contains the higher level of THC. Sorry to burst your bubble (if that’s what you’re here for).

If you’re interested in learning more about the difference between hemp and marijuana, we take a deep-dive into the topic in this article.

History of Hempcrete

Surprisingly – hempcrete is not a new discovery. Archaeologists have dated its prevalence back thousands of years. There are ancient remnants of hempcrete throughout Europe, including a bridge from the 6th Century AD in Southern France. More recently, hempcrete projects in France have remained structurally sound for the last 40 years – and getting stronger by the day.

While hemp has paved its way into many constructions across millennia, legislation against its use took place in the United States in 1937. This was unfairly due to economic competition with cotton, timber and synthetic plastics – as well as fear-mongering publicity claiming that the plant caused violent crimes.

You see, the cannabis plant is like that over-achieving kid in school who is good at everything. And the legislation against it – well, we’ve all heard of tall poppy syndrome.

It wasn’t long before Australia (and most of the world) followed suit with the US – and cannabis was sent to the naughty corner. The entire plant, including its wonderful benefits, became tarnished with the same brush as harmful recreational drugs. And so, the miracle of hempcrete died along with the thousands of cannabis plants sprawled across the world. Now, with hemp being legalised in Australia, hemp is slowly making its way back to the limelight it deserves.

Advantages of a Hempcrete House

This is where things get really exciting for those of us interested in eco-friendly homes – it’s time to take a deep-dive into the wonderful benefits of hempcrete:

Excellent Thermal Properties

Hempcrete has excellent thermal conductivity (ability to conduct heat), and thermal mass (ability to store heat energy). And this energy (warm or cold) that is stored within the walls is released slowly, meaning it neutralises the outside temperature fluctuations – keeping your home at a stable temperature! Many other lightweight synthetic insulators, like polystyrene and styrofoam, don’t have the capacity to store heat – and that’s when we turn to our faithful (and unsustainable) friends: the heater and aircon.  

Moderates Humidity

Due to the pores found in hempcrete – the flow of air and moisture between the walls promotes a healthy environment. These pores act like a giant moisture regulating sponge: absorbing humidity in the air when relative humidity is high, and releasing it again when it is low. This helps to prevent nasty mould and mildew growth… it’s the perfect bioconstruction material.

Fire and Pest Resistant

Lime is to termites & critters what brussels sprouts are to humans: highly unappetising (no offence, if you’re a brussels sprouts lover – we’re not here to judge). This means that common household pests avoid hempcrete at all costs. The lime in the hempcrete mix also makes it fire resistant, complying with the Australian standards of construction in bush-fire prone areas. Recent studies have found that the consistency of the hempcrete mix affects its fire rating.

Hemp Has a Short Life Cycle

They call it ‘weed’ for a reason – it has the ability to grow anywhere (we’ll excuse you, Antarctica). It requires minimal herbicides and pesticides, which helps to revitalise the soil. It is also quick to grow – hemp plants are able to be used in construction after 3-to-4 months of growth, compared to wood which takes years.

CO2 Absorption

Not only is a hemp house good for your health – its good for the planet. Hempcrete is what we call “carbon-negative” – meaning more carbon is removed from the atmosphere by the plant than what is emitted through its growing & processing. This reduces atmospheric CO2 levels and has the potential to help reverse global warming. Hempcrete becomes harder over time as it absorbs more CO2, meaning your building will become stronger while benefiting the planet. Phenomenal!

Disadvantages of Hempcrete

At this point, most people start to wonder – what’s the catch with this miracle material?

The truth is that since hempcrete has been pushed away from the public eye for so long, it may be hard to find a construction company that is experienced with its use. Many architects are also unfamiliar with the product, making it difficult to come up with designs. Due to this lack of familiarity, hempcrete can sometimes cost more than its concrete rival. It has also been described as labour intensive work.

In saying that – there are some extraordinary people who are making waves in the hempcrete industry, including the Australian building company: Hemp Homes Australia. You can learn more about them here.

Hempcrete for a Greener Planet

In a time where climate change and consumption undoubtedly butt heads, hempcrete is a shimmer of hope. Perhaps it offers a shift in perspective – one that focuses on building our way to a better future, rather than restricting our actions to get there. It is a solution that appeals to climate change advocates, governments and businesses alike. An unlikely harmony – but one to be embraced.

Thank you Copy Circle for this excellent guest article. Please note: this is only a short overview on hempcrete in Australia – as it’s a vast and complex subject. If you’re interested to learn more – comment below!

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