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Sustainable building: hempcrete houses
Hemp has been used to build and create since time immemorial: archaeologists uncovered hemp cords on sites in (today’s) Taiwan and remnants of hemp cloth in Mesopotamia dating back to as early as 8000 BC. In some archaeological circles, hemp is believed to be the oldest example of human industry.
Traces of hemp being used by ancient civilisations criss-cross the world. Hemp materials have been unearthed in Asia, Europe, Africa, and South America. Religious scripts, from Hinduism to ancient Persian religions, cite hemp as a “Sacred Grass” or “King of Seeds”.
The plant was a vital part of many aspects of life: clothing, rope, paper, food. One of its uses – in building materials and tools – is reappearing in the modern world. Increasingly, people are looking to hemp as an answer to sustainable building.
How can hemp be used in construction, and what are the benefits?
Hempcrete vs concrete: the answer to sustainable building
The word hempcrete has become synonymous with the industrial hemp construction world. But what exactly is hempcrete?
Hempcrete is an energy-efficient, water-smart building material – made by mixing hemp with a lime binder and water – that produces a far smaller carbon footprint than other building materials. It’s often used as an environmentally-friendly alternative to concrete.
The part of the plant used for making hempcreteis the strong, woody cellulose of the stem – this is considered a waste by-product from hemp fiber growing (for oil, seed and fibers). By using the hemp shivs to create hempcrete, the entire plant can be utilised.
Unlike energy-intensive concrete, hempcrete requires no heat to produce. It is created by wet-mixing the stem with a lime-based binder to create a material that can be cast into moulds. The material can be formed to slot between the studs of a house as building blocks or bricks. It can be used for walls, floors and roof insulation.
A vapor-permeable material,hempcrete absorbs water when it’s raining and expels it when it’s sunny. The result? A naturally regulated internal humidity, and no problems with mould or rot.
It’s also a better insulator than traditional concrete. Hempcrete walls, floors, ceilings and roofs have incredible thermal properties – another reason it’s an environmentally-friendly building material as keeping heat inside is key to reducing energy use. Many of the conventional synthetic insulation materials have massive carbon footprints – due to the energy used in extraction of the raw materials, their processing, transport, use, and eventual disposal. As a plant-based building material, hempcrete does not contain any of the harmful volatile organic compounds found in other materials – and will naturally decompose.
What is a carbon-negative house?
As hemp grows, it absorbs carbon from the air. (Infact, it is one of the most effective carbon capturers on the planet: it’s rapid growth makes it one of the fastest CO2-to-biomass conversion tools available, more efficient than agro-forestry or any other crop).
Hempcrete is a carbon-negative material. This means more carbon is taken out of the atmosphere in the life of a growing hemp plant than is emitted as a result of production and application of the building material.
So, if you build a house using sustainable materials, including hempcrete, you could live in a better-than-zero-carbon house. A carbon-negative house!