Hemp has been used in multiple ways throughout history, and today offers a sustainable material for construction.

Hemp bricks: insulating and sustainable

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Benito Díaz

Biofuel, plastics, textiles, paper… hemp fibre has proven to be one of the most versatile natural materials in the world. Hemp has been used in multiple ways throughout history, resulting in objects of legendary quality and durability.

This plant, the male expression of the cannabis plant, has accompanied humanity since the dawn of times and its multiple properties have been exploited for centuries and up to the present day, adapting to needs in: the manufacturing of bioplastics, automotive industry, electrical batteries, offering a green way to the paper industry or in the latest fashions in clothing.

Hemp as a construction material

Used since Julius Caesar’s times, Romans discovered the properties of mixing clay or adobe with hemp fibres to obtain a natural and light concrete used in the construction of colonial villages. Although some traces can be found in certain archaeological sites, other uses as ropes or textile could have displaced its use away from construction.

It was during the 1990s that French builder Charles Rasetti prepared a lime mortar and hemp fibre mix to make some modifications in his own house. The material obtained turned out to be perfectly adequate for his idea, and he decided to extend its use all over the country. France is still today the leader in cultivation and manufacturing of products derived from industrial hemp.

The USA have pushed forward hemp cultivation since its legalization in the state of California, in spite of being the country that promoted worldwide prohibition and started the War on Drugs, leading to the persecution and suffering of millions of people. In 2010 North Carolina saw the construction of the first house built with cannabis in the country. According to Adam Popescu in the New York Times, there were more than 50 in 2018.

The positive experience has made other countries show interest for this material, such as United Kingdom, Canada or New Zealand. An expanding industry that, nevertheless, counts with few specialized constructors in Spain. There are barely 300 single-family homes of one or two floors, especially in rural areas.

Nowadays

Mönika Brümmer is a German architect who brought hemp back to life and has been producing it from 1999 in Guadix, Granada. Cannabric is the company that produces the material: mixed with clay instead of lime mortar, it is even more sustainable and adaptable to our climate. “I could not find ecological blocks and pieces in the south of Spain so I decided to produce a block that I designed. I adapted its features to the climate conditions of the Mediterranean region. It’s the only prefabricated formulation of its kind so far. In order to introduce something like this in the market, a lot of patience is needed”, said the architect to La Información newspaper.

They’re single-family homes or buildings of up to 300 m2 for most of them”, says Brümmer. “It is this type of customer who shows interest in these constructions. In the big building works these blocks can’t be part of a bearing wall, but they can as a building envelope; the problem is I would need certifications that are not viable with my current production volume”. According to the architect, the investment needed to start a competitive industry of hemp transformation is significant. That is why no one set a factory in Spain until Cannabric was created. “In Guadix in particular, and in Spain, other construction materials producers have closed down while we have survived, and that is because the bioconstruction market is a growing one and has not been as affected by the recession as the rest”, claims Bümmer.

Cannabric’s catalogue includes a wide range of products apart from the bricks, such as insulation panels, tapestries for the walls and acoustic filters, among others.

Ecological advantages

Hemp is considered industrial when its THC percentage is lower than 0.2%. Easy to grow, it has a limited impact in the environment due to its capacity of regenerating the soil. It needs less water than the production of cannabis.

The thermal insulation made out of these materials ensure an important saving of energy, as well as being totally biodegradable in contrast to other possibilities, like the long time used asbestos. It is also resistant to combustion and dampness and its composition is so robust that it can support several floors without foundations.

On the other hand, hemp and other ecological materials can not be mixed with cement or other traditional construction materials, since that would cause them to lose their thermal, acoustic and bioclimatic properties. These ecological materials suffer transformations and can even lead to illnesses if not properly used.

Unfortunately, the lack of investigation about the properties of hemp keeps it as an “unknown” material. Moreover, the certification necessary for its production and other bureaucratic difficulties make the production in a large scale impossible. That is why it is not used in relevant building works yet.