Alternative construction material promises warmer homes

Reduced fuel bills from better insulated homes is the ambition of product manufacturer Unyte, which is extolling the virtues of specifying construction materials featuring hemp, a derivative of cannabis plants.

It also says that use of its ‘hempcrete’ building blocks allow for more ‘breathable’ homes as moisture can escape more easily; helping to reduce the build-up of damp and mould which can cause respiratory illnesses.

In addition, the use of the hemp could help in the drive to decarbonisation of the built environment at scale, as the material can be used to capture and store carbon emissions.

“Hemp will grow anywhere in the UK, and takes about four months to grow up to four metres tall,” said company founder Jamie Bartley.

“We worked closely with both the Home Office and the Department for Environment, Food & Rural Affairs around policy and legislation, and were successful in pushing for changes which came into place this year.”

He explains that Government reforms now allow farmers to apply for a six-year licence to grow hemp – rather than a previous maximum of three years – making it easier to plan their crop rotations.

Licenced farmers can also now grow hemp anywhere on their land, rather than having to specify which fields will grow the plant.

 “The challenge now is to develop processing infrastructure to allow these products to be mass produced and scaled into the volumes that we need them to be.” Jamie said that the thermal performance of hemp represents a big advantage of the material’s use in construction.

“There are houses on the north shores of Scotland with hemp that do not have any internal heating on all year round; the internal temperature won't change between 16 and 18 degrees, so it hugely reduces the energy requirement for heating or cooling those properties.”

Jamie Bartley of Unyte Group

Jamie first investigated the potential for hemp in construction when looking for natural materials that could help to remediate poor quality, contaminated land and improve soil.

“That was my initial touch point, but once I started researching it, I realised it could do so much more than just clean up soil. Anything made from petrochemicals can be made from hemp, with the right infrastructure and processing.”

Now the company has an academy that trains installers and technicians needed for retrofit.

“We are very focused on scaling hemp as a carbon negative construction material, which we can then use for both new build and also retrofit. We are gaining traction, getting support and need to make it comparable on cost with other materials.”

Another aim is for the benefits of embodied carbon to be considered more by the sector alongside cost, quality and procurement, to help make hempcrete and hemp insulation more appealing for specifiers. “We need early adopters to help push the use of hemp forwards,” Jamie said.

The use of hemp in buildings is not entirely a new idea or one that is reserved for residential properties. Jamie said that sensitive artifacts in the Science Museum are stored in a room built from hemp-based materials, as it absorbs moisture from the atmosphere and releases it back steadily over time.

He adds that hemp represents a huge potential in property retrofit and new build. “There are around 27 million properties still to be retrofitted in the UK and Government is talking about building 1.5 million new homes in this Parliament.

“Hemp will not be suitable for every project, but could certainly be used in a large chunk of those. As soon as we start to better value embodied carbon alongside cost and quality, we could see a real change in the adoption of bio-based materials.

“There are several local authority leaders trying to look at whole life carbon assessments at a planning stage, which will make developers really conscious of the need to consider alternative materials.”

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