This is the fifth post in our Super Natural Materials series – you can view the whole series here.
Hemp: a versatile material
Hemp is a plant that holds extraordinary history, from its use as paper, to hemp plastic, to its versatile uses in the construction industry. Natural building materials require minimal refining and processing, while simultaneously reducing the detrimental impact the construction industry has on the environment.
France is one of the countries to truly embrace and endorse the use of hemp in construction; for years it has been used as the material of choice in the conservation of timber frame buildings.
After processing the stems of the plant, two different materials are produced: hurds and fibers.
Hurds can be turned into products such as roofing tiles, wallboard, fibreboard, insulation, panelling, bricks and more recently, structural timber/hemp building blocks.
Fibers, on the other hand, are used in place of straw for bale wall construction or alternatively can be blended with mud for cob style construction.
For those asking – no, you can’t smoke it. The cannabis plant is resourceful in many ways and hemp happens to be one of them. This post will explore some of the top benefits of building with hemp, plus some examples of diverse hemp projects from our work and other designers.
Benefits of building with hemp:
◦ Low embodied energy – doesn’t require much processing in its production, meaning that it is beneficial to the environment.
◦ Carbon storage – in its lifespan, it absorbs a large amount of CO2 from the atmosphere. During its growth stage, it will lock away up to 2 tonnes of CO2 per tonne of fibre harvested.
◦ Great thermal insulation properties – it’s a medium density insulation material which is safe, efficient and durable. Low conductivity and a higher thermal mass enable it to retain heat and regulate thermal performance for a comfortable internal environment.
◦ Breathes, prevents condensation – it can absorb up to 20% of its weight in moisture without deterioration in its performance, unlike most other insulation materials. It can then release this moisture when required, regulating the internal humidity. Hemp is also mould-resistant.
◦ Non-flammable – when mixed with lime in Hempcrete construction, it is completely non-flammable.
◦ Lightweight – which increases its range of applications in the construction industry, can be used in lofts, walls and inter-floors.
◦ Recyclable – it’s biodegradable and non-toxic so it’s truly circular – it can completely decompose.
◦ Sustainable – hemp can be grown year-round and only takes up to 100 days to reach full growth.
◦ Low maintenance – it requires very little water to grow and does not require herbicides or chemical pesticides.
Examples of building with hemp:
Opened in August 2012, M&S Cheshire Oaks has won multiple awards and is their biggest, greenest store. It has been designed to be the most carbon efficient store of theirs to date with an architectural and design strategy to address various areas of sustainability at once. It is the first store to use hemp and lime external wall panels which have excellent insulation properties resulting in the store losing less than 1°C of heat overnight compared to 9°C in other store environments.
America’s first hemp house in Asheville, North Carolina. The house is made with hempcrete and boasts an abundance of eco-friendly features. Using hempcrete allows a solid yet breathable wall. Hemp hurds were mixed with lime and water on-site and poured in-between the exterior supporting timber studs.
Hemp Cottage in County Down, Northern Ireland. Shortlisted in the Top 10 UK Eco-Homes, the house’s main frame was built from locally sourced Douglas fir, with the stud work being cast with a hemp lime composite. Explore more about this home here.
Why do architects like working with hemp?
“It’s a natural insulation material; it’s hygroscopic, so has the ability to hold onto moisture, which allows it to act as a humidity regulator and of course, it’s recyclable, that’s why I used it on my house for insulation.”
– Mark Pellant, Director of Koru Architects
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