Introducing a New Building Material - Hempcrete

Introducing a New Building Material - Hempcrete

26th September 2017

Here at Safety Fabrications we keep an eye open for all the new developments in the construction industry so that we can keep our readers up to date with current practice.  We often come across innovative new building materials which we report on and we’ve recently come across “hempcrete”, a bio-composite made from the inner woody core of the hemp plant mixed with a lime-based binding agent.  Because the hemp core (also known as “shiv”) contains high quantities of silica, it binds well with lime, to produce a lightweight, cement-like insulating material which weighs a fraction of the weight of concrete.

Hempcrete was first developed in France to increase thermal performance in medieval timber-frame buildings.  It’s very similar to timber in the way in which it controls moisture on a similar rate to existing wooden elements of the building.  This has led to it being the material of choice in repairing and increasing thermal performance in traditional and historic buildings.  It can be applied as a wet-mixed loose filler which wets and holds its shape, meaning it is ideal for use on uneven walls and timber-frame walls.

As a safety feature, hempcrete is surprisingly fire-resistant, we watched a YouTube video of a piece of hempcrete being tested by having a blowtorch flame pointed at it and after 8 minutes, the material was hot, but it had blackened where the flame had touched it but not even smouldered, let alone caught alight. 

Hempcrete will regulate the temperature and humidity in a building, in some cases eliminating the need for heating and cooling systems which can lead to huge energy savings.  Hempcrete is carbon negative, meaning that it’s better than zero-carbon materials.  More atmospheric carbon is locked away in the structure of the building than was used in its production and use!  With the construction industry responsible for about 60% of all of our carbon emissions in the UK (through the energy used in the construction phase and by the occupants using the building), using it in construction projects is a great way to achieve the government’s target of zero-carbon.

Hempcrete is also water-proof, meaning that it’s suitable for using as a finish on both interior and exterior walls.  It performs well in all types of climates, including cold, wet ones and is seen as low maintenance as pigment can be added and it can be hosed down to clean it, instead of having to be painted on a regular basis.  Hempcrete is also earthquake resistant when reinforced with rebar.  Hemp is a low-cost crop to produce and the length of its fibres make it a versatile option for creating strong, energy efficient structures that are eco-friendly.  When used to make particle board, it delivers a product with twice the strength (but a fraction of the weight) of similar products made from wood – and, as an added bonus, it tends to hold nails better.

However, at present, the production of hemp is illegal in many countries because it comes from the cannabis sativa plant which produces marijuana.  The advantages it can bring, along with the fact that it’s also termite and rodent resistant means that we’re likely to see industrial scale production of hempcrete for building homes in the future.