The Hemp Renaissance: Is this Ancient Fibre the Future of Building?
Hemp renders and mortars are hardly the new kids on the block. In fact, they have played a pivotal role in industry for centuries. However, in a world increasingly fixated on U-values, thermal bridging, and carbon footprints, this versatile material is enjoying a well-deserved resurgence.
From the external facade to internal plastering, hemp offers a compelling, eco-friendly alternative to the gypsum and cement-based norms. But does it hold up against modern 2016 insulation standards? Let’s delve into the history of hemp and see if it’s ready to tackle the demands of modern British construction.
A Storied Past: From Ancient Currency to Modern Innovation
The history of hemp is nothing short of fascinating. Cultivated for millennia in civilisations as diverse as Ancient China and Mesopotamia, it was prized for its fibrous strength and medicinal qualities. It was so vital to the economic engine of the past that it was occasionally used as actual currency.
Fast forward to the 21st century, and the narrative has shifted from rope and canvas to sustainability and innovation. The modern application of hemp spans textiles, food, and, crucially, construction. Its durable fibres are now replacing environmentally damaging synthetics, proving that sometimes the old ways are indeed the best.
With the UK’s push toward “fabric first” building standards, researchers and entrepreneurs are unlocking hemp’s potential for everything from biofuels to biodegradable plastics. It represents a bridge between our agricultural past and a sustainable future.
The Green contender: Hemp vs. Traditional Materials
As we grapple with the targets set out in Part L of the Building Regulations, the embodied carbon of building materials has come under scrutiny. Traditional concrete and gypsum plasters are energy-intensive to produce. Hemp renders, by contrast, are a breath of fresh air.
Why Hemp Wins on Sustainability:
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Low Embodied Energy: Hemp renders are composed of natural fibres that require minimal energy to process.
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Carbon Sequestration: Hemp is a rapid-growth crop, maturing in just a few months. During this time, it absorbs vast amounts of CO2, making many hemp products carbon-negative before they even leave the farm.
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Minimal Chemicals: Unlike many industrial crops, hemp grows like a weed (literally), requiring little to no pesticides or herbicides.
The Thermal Advantage
In the context of 2016 insulation standards, hemp is a standout performer. It offers superior thermal inertia compared to conventional masonry. This means buildings stay warmer in the winter and cooler in the summer, flattening the curve of energy consumption. Perhaps most importantly for the damp British climate, hemp renders are breathable. They allow moisture to evaporate naturally, mitigating the risk of “sick building syndrome,” mould, and the condensation issues often caused by sealing buildings too tightly with non-permeable materials.
Hemp in Construction: More Than Just a Niche
The construction industry is notoriously slow to change, but the benefits of hemp are becoming impossible to ignore.
1. Internal Plasters
Hemp internal plasters are becoming the finish of choice for the eco-conscious architect. Blending hemp fibres with lime, these plasters regulate indoor humidity (hygroscopic performance) and improve air quality. They contain no Volatile Organic Compounds (VOCs), making them ideal for households with chemical sensitivities. Plus, visually, they offer a stunning, tactile texture that standard gypsum skim simply cannot match.
2. External Renders
Applying hemp render to the exterior acts as a thermal jacket for a property. It shields the structure from weathering while preventing moisture from becoming trapped inside the wall—a common failure of modern cement renders on older properties. It also helps combat the ‘Urban Heat Island’ effect by reflecting heat rather than absorbing it.
3. Hempcrete (Hemp Cement)
This bio-composite mixes hemp shiv with lime and water. While research is ongoing regarding its use in load-bearing capacities, its current strength lies in its thermal and acoustic insulation properties. It is lightweight, reduces the load on foundations, and locks away carbon for the lifespan of the building.
4. Hemp Bricks & Insulation Panels
For modular construction, compressed hemp bricks and insulation panels offer a dense, fire-resistant solution. They provide excellent thermal resistance and, crucially for safety standards, natural fire retardancy without the need for toxic chemical additives.
The Challenge: Hemp and Humidity
No material is perfect. While hemp is excellent at managing moisture, it is not impervious to it. In exceptionally humid environments or where there is constant water ingress (like a leaking pipe or rising damp), the high absorbency of the fibre can become a liability, potentially leading to rot.
However, the industry is adapting. Manufacturers are currently developing specialised renders with enhanced moisture resistance to ensure they can withstand the rigours of a wet British winter without compromising breathability.
The ECS Hemp Render Product Challenge
At ECS, we are committed to finding the “Holy Grail” of sustainable rendering. We are currently inviting manufacturers to submit their hemp render products for rigorous testing. Winners will not only be showcased but stocked by ECS.
The Current Status:
To date, we have yet to find a product that ticks every single box. We are continuing our search.
The Criteria:
To meet the demands of modern application and 2016 thermal standards, the winning product must meet the following specifications:
Application: Must be suitable for both machine spray and hand application.
Thermal Performance: Thermal conductivity lambdaof 0.045 W/mK or better.
Build-up: Capable of holding a 4cm thickness in a single coat.
Moisture Control: Demonstrated resistance to humidity while retaining dehumidifying properties.
Finish: Must be capable of being polished or smoothed for a high-quality decorative finish.
Hemp renders represent a convergence of heritage and high-tech performance. With their impressive thermal properties and aesthetic versatility, they are poised to become a staple of British construction. We just need the right product to lead the charge.
Are you the manufacturer who can crack the code?