By Nidhi DhullReviewed by Susha Cheriyedath, M.Sc.Sep 25 2024A recent news article published in Euronews presented hempcrete, a bio-based building material, as a sustainable alternative to conventional bricks and concrete with a huge environmental footprint.
Study: Hempcrete: The green brick taking on the challenge of climate change. Image Credit: BBstockimage/Shutterstock.com
Background
Hempcrete has emerged as a green building material, lately garnering the attention of environmentally responsible architects and house owners due to its potential as a sustainable substitute for environmentally hazardous concrete and bricks. It is an optimized mix of hemp shiv, hemp plant’s dried inner core, with water and lime.
The early instances of hempcrete usage in construction date back over 1500 years. Hemp plaster from the sixth century is still present in the United Nations Educational, Scientific and Cultural Organization (UNESCO)-tagged Ellora Caves, India. Additionally, hemp mortar was found in ancient Merovingian bridge struts in France. Consequently, France led the modernization of hempcrete in the 1980s, when hempcrete was cast onsite like concrete today.
However, obtaining the right hempcrete mix was tricky for laypeople as excess of any of the three constituents made the product runny and weak, while inadequate caused crumbling. Moreover, drying time was also challenging as cast hempcrete may take four to six weeks to cure in fair conditions, but cold, damp winters slowed the curing to at least six months, limiting its mass usage across northern Europe.
Hempcrete for Sustainable Construction
Despite several challenges, hempcrete’s eco-friendliness has led to its introduction into the conventional construction industry. Notably, contrasting traditional crops, hemp does not require several fertilizers or pesticides for protection during growth. The tall, fibrous hemp used in buildings quickly grows and can be cropped close together, controlling weeds naturally.
Hempcrete production requires energy but has an unlimited lifespan compared to synthetic wall infills and insulation. Moreover, its main ingredient is a renewable crop whose production requires significantly less energy and carbon. Consequently, experiments began in France and Belgium in the early 2000s to overcome the hurdles preventing the realization of hempcrete’s full potential in mainstream construction.
The advancement of the hempcrete block or ‘green brick’ proved to be a milestone in removing the need for special skills and guesswork in hempcrete usage. This lightweight fibrous block expanded the application of hempcrete without compromising its eco-friendliness.
Moreover, it does not contain volatile organic compounds and retains hempcrete’s moisture absorption, acoustic, and thermal conduction properties. It has become a lightweight, consistent, and reliable product that is easily transportable to construction sites and usable without special training.
Comparison with Concrete
Concrete is a reinforced structural construction material that can support itself, whereas hempcrete is used around a wooden, concrete, or steel frame. The latter is more like insulation with no harm to the environment. Additionally, hempcrete can support itself as blocks for use in multi-story buildings.
However, most examples in South Africa, the Netherlands, and France demonstrate its usage around a frame. Structural applications of hempcrete are being further explored by adjusting the recipe to make it par with other construction materials without using unsustainable ingredients. This has become more prominent in the post-Corona virus world, where homes have become a place to live and work for many.
Man-made insulations, such as fiberglass and polyurethane, act as an obstacle between heat and cold but heat up and cool down rapidly. Alternatively, natural materials like hempcrete heat up gradually and retain the heat for longer through the decrement delay process. This process is ideal for today’s world, where individuals spend more time at home, requiring more frequent heating in the colder months.
Usage in Europe
Europe has emerged as the hub of major companies in the hempcrete world. It is regularly used to retrofit old structures and prepare the core of new construction in France, Belgium, Netherlands, Germany, and Italy. Comparatively, the United Kingdom is a few steps behind with 300-400 houses built with hempcrete, but the gap is closing rapidly.
Isohemp, a Belgian company established in 2011, has become a major hempcrete producer in five countries. It produces over a million hempcrete blocks annually and claims to save 18,000 tons of CO2 through various projects.
The future of hempcrete in construction is expected to be in prefabrication using modular approaches similar to timber-framed houses. Companies in Britain are building traditional houses with hempcrete that appear identical to estate homes but with superior eco-performance. Additionally, retrofitting cold and leaky pre-1940s housing stock is being considered.
Overall, the complete potential of hemp and hempcrete is yet to be realized. BMW (Bayerische Motoren Werke) currently uses a lightweight hemp polymer in the doors of its i3 electric cars. Alternatively, hempcrete is used in south Italian earthquake zones as a flexible construction material that can handle seismic movement instead of rigid and brittle concrete. Such innovative uses of hempcrete assure its bright future as a green construction material.
Journal Reference
Myrie, G. (2024). Hempcrete: The green brick taking on the challenge of climate change. Euronews. https://www.euronews.com/culture/2024/09/01/hempcrete-the-green-brick-taking-on-the-challenge-of-climate-change
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