Hemp is making a comeback as a building material in France – a decade after one of the country’s largest construction firms lost money investing in it.
Saint-Gobain, which makes plasterboard, insulation and other building materials, formerly launched a line of hemp-based insulation panels to replace fibreglass and rockwool insulation.
However, after having the product in builders’ supply depots for two years, Saint-Gobin withdrew from the market because of poor sales – the panels were usually between 10% and 20% more expensive than standard ones.
The company, which has an insulation brand called Isover, now offers wood fibre or recycled textiles as its main alternative insulation products, as well as traditional materials.
One of the pioneers of the hemp industry in France, however, former professional surfer Vincent Lartizien, is building a new factory to make concrete blocks with hemp incorporated in them.
The blocks will be the same size as the concrete blocks used all over France, but the hemp greatly increases their insulation properties.
“Builders and architects are approaching us because the new building standards RT 2020 mean that ordinary concrete is very difficult to work with,” Mr Lartizien told The Connexion.
“They need something which is lower in carbon dioxide counts and which has better thermal efficiency.”
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While hemp and cannabis come from the same plant species, the former typically has lower concentrations of the psychoactive component tetrahydrocannabinol (THC).
It can be legally grown in France – farmers simply need to make a declaration first. Many complain, however, that although hemp is an ideal crop for plant rotations, prices are so low that they can hardly afford to grow it.
Some are lobbying for the crop to be subsidised when the EU’s agricultural policy is next revised in 2027, under the environmental services payment schemes used to promote good farming practices.
As well as being mixed with concrete, hemp can be transformed into a ‘wool’ used for insulating panels.
Hemp stems can also be pressed with resins to form beams that are as strong as wood but significantly lighter.
There are small factories transforming hemp across France. One of these, Gatichanvre in Prunay-sur-Essonne (Ile-de-France), has just invested €3million in new machines which take the raw hemp from farmers and transform it into straw, ready for further uses.
When he started his hemp business, Mr Lartizien concentrated on hemp food supplements, salad oil, clothes and cosmetics rather than construction.
“The market has moved and there is now enough demand for building materials with hemp in them to be competitive,” he said.
