Building With Hemp

BUILDING WITH HEMP by Matt Muldoon

Hemp and humankind share a symbiotic relationship that stretches back into prehistory. The consumption of psychoactive strains of hemp - better known as cannabis - is well documented; but hemp is a crop with a wide variety of uses. Its fibres are used for high quality rope, cloth and paper; as a food it contains a large proportion of essential fatty acids and amino acids; and it has medicinal anti-inflammatory properties.

Hemp’s importance in East Anglia can be appreciated through the wealth of place names such as Hempnall, Hempstead and Hemplands. After a halt in cultivation in the 20th Century, hemp is being grown in the region once more as a crop which can be used in building. Dried hemp hurds are mixed with lime to create hempcrete. This hemp-lime mix sets hard like concrete, but unlike concrete it is attractive, lightweight, flexible, breathable, and also a good insulator. Hempcrete is cast around a timber frame to create high performance buildings which have a positive impact on the environment.

With their excellent insulation and breathability, hempcrete buildings are snug and regulate their own humidity efficiently. Hempcrete also provides thermal mass, meaning that it can store heat and release it slowly, helping to equalize temperatures between heating and cooling cycles. This creates a very happy and healthy living environment which is easy to heat and much less humid than masonry structures. Hempcrete can be used for walls, roofs, and solid-yet-warm floors. It’s also easily moldable into flowing curves and other interesting features. Since hempcrete is cast into a timber frame, it is also an excellent choice for the repair of old oak frame structures, providing a sympathetic alternative to daub and better thermal performance. It is comparable in price to brick and block, yet consistently outperforms it in terms of thermal insulation and humidity regulation.

The production of hempcrete even has a positive impact on the environment. The indigenous hemp crop grows voraciously in East Anglia without the need for agrochemicals, with one hectare of land producing enough hemp for a small house within 14 weeks. The crop protects against soil erosion and naturally drowns out weeds, so it’s easy to grow according to organic principles. Lime, the other essential ingredient in hempcrete, was produced all over the country for hundreds of years before the wide-spread adoption of cement during the 20th Century. Lime production releases 80% less carbon dioxide than cement production. And, since hempcrete “locks up” organic matter, it removes 110kg of carbon dioxide from the atmosphere for every cubic metre installed. This makes hempcrete a material which is better than carbon neutral.

It’s easy to see why hempcrete is gaining popularity - it creates warmer, drier homes and has a positive impact on the environment. It’s not a complicated material; it’s made of essentially natural ingredients which have served us well for millennia.

From Inspirations Magazine April/May 2009 edtion.