Euro News: Hempcrete: The green brick taking on the challenge of climate change

It really doesn’t look like much, but hempcrete is the green building material that’s got eco-savvy homeowners and architects excited by its potential to be a sustainable alternative to environmentally expensive bricks and concrete.

But although hempcrete seems like a very modern building material, it has a history stretching back over 1,500 years.

Hemp plaster from the sixth century still lines the walls of the UNESCO-designated Ellora Caves in India, and hemp mortar has been discovered in ancient Merovingian bridge abutments in France – which is fitting, as France was at the forefront of the 1980s drive to modernise hempcrete and introduce it to a new generation.

Back then, wet hempcrete was cast onsite, as concrete is today, but the challenge of getting the mixture right made it a tricky product for laypeople to use. Too much of any of the three ingredients could make the material runny and weak, while not enough could cause crumbling.

Its drying time also posed problems. In fair conditions, cast hempcrete can take between four and six weeks to cure. But a cold damp winter could slow the process to at least six months, restricting its mass use across northern Europe.

Impeccable environmental credentials

Despite the challenges, hempcrete’s undeniable environmental credentials have meant it was a case of when, rather than if, it would muscle its way into the mainstream building trade.

Liam Donohoe, chief operating officer at UK Hempcrete – a Derbyshire-based company designing and supplying materials to building projects using hempcrete – tells Euronews Culture that sustainability plays a part in every area of the product’s development.

“Hemp, unlike conventional crops, doesn’t require a lot of fertilisers or pesticides to protect it as it grows. The type of fibrous hemp usually used in construction is a tall plant that grows quickly and so can be cropped and planted quite close together, naturally suppressing weeds,” he says.

“I’m not saying it takes no energy to produce hempcrete, it does. But when you compare it to man-made insulation and wall infills, it has an unlimited life span and the primary ingredient is a renewable crop that costs a lot less energy and carbon to produce.”

…green brick taking on climate change…

Garfield Myrie

Research and development changed everything

Experiments in France and at Belgium’s University of Leuven in the early 2000s saw researchers begin tackling the barriers preventing hempcrete from realising its full potential as a mainstream building product.

The eureka moment was the development of the hempcrete block or ‘green brick’, which took the specialist skill and guesswork out of using the material.

The lightweight fibrous block opened up a new world of possibilities for the material without diminishing any of its eco-credentials. It is free from volatile organic compounds (VOC) and indefinitely retains its acoustic, moisture absorption and thermal conductivity properties – in sharp contrast to synthetic insulation that decompresses over time to become less effective.

It is now a consistent, lightweight and reliable product that can be easily transported to sites and used by jobbing builders without extensive training.

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