Hemp Houses, The Secret of Building Sustainable Homes.

Today, hemp bricks are being used to build eco homes in the Province of Granada, Spain. Hemp as an industrial product has been around for thousands of years. After a period of decline it is now beginning to show a re-emergence in this eco-age as a sustainable building product.

Hemp comes from the Anglo Saxon word ‘haemp' and is the popular name for plants of the cannabis genus. Hemp usually refers to the strains of the plant cultivated exclusively for industrial use as opposed to cannabis which is associated with pot and similar drugs.

Hemp has a huge variety of uses but continues to be overshadowed by the cannabis connotation of illegal drugs, with which it is often confused. However hemp can legally be grown, under licence, in many countries, including the European Union countries and Canada.

Cannabis sativa L. is the variety primarily grown for industrial purposes, it is a fast growing plant and has been cultivated for many thousand of years being used to make rope, clothing, paper, hemp oil and medicines. Growing hemp improves the condition of the ground and reduces ambient contamination. It is a robust plant that requires neither herbicides nor pesticides during its cultivation.

Hemp as an industrial material has a ten thousand year history. The first recorded use of hemp was as a cloth fabric, found in China as far back as 8000BC.C. Circa 4000B.C. hemp started to be used, again in China, to make ropes and as food. 2000 years later, the Chinese hemp oils and medicine were in use. By 1000B.C. its use had spread to India and Greece where the first instances of hemp paper were found.

By the 6th century hemp was being used in Europe in some amazing ways, in France a hemp reinforced bridge was built and it is still in use today. The hemp fibre also found uses in sailmaking, caulking materials, fishing nets and lines. Later hemp was used to make a form of butter and even beer. By the 15th century Renaissance painters were using hemp canvases.

Today industrial hemp is used to make a staggering variety of products ranging from medicines, body care products, building and insulating materials, clothing, textiles, food, fuel, livestock food and bedding, plastics and paper.

In the building industry hemp bricks, because of their sustainability and excellent insulation properties, are being used to construct external and internal walls of ecological homes. In this area of Spain the external walls of an eco house will consist of a eco-bricks, manufactured in Guadix with the proprietary name of Cannabric®.

Cannabric® derives its properties from industrial hemp fibres (cáñamo). The hemp bricks are made up of industrial hemp fibres, slaked lime and a mixture of innert mineral materials. The bricks combine the functions of a load bearing wall that is fire-resistant and does not require the addition of thermal or acoustic insulation.

The most important component of the eco-brick is industrial hemp which has a very low thermal conductivity (0.048W/m²k) producing a brick with vastly superior insulation properties against both cold and heat. The mineral component of the bricks gives them their mechanical strength. Being a solid brick, with a high specific heat, it has the optimal thermal properties to protect against heat.

These characteristics make hemp bricks the ideal choice in areas of southern Europe where there are extremes in temperature through summer and winter.

The mechanical strength of the block starts with formation of insoluble hydrates. The strength increases over time with the carbonation of the free lime, (a constituent of slaked lime) by moisture and carbon dioxide present in the air. Another important factor in the progressive curing of the eco-bricks is the gradual petrifaction of the industrial hemp by the lime and minerals present in the bricks.

Due to its unique composition the hemp bricks allow the transpiration and diffusion of water vapour between the inside and outside of the building equalising humidity within the building thus avoiding humid and cold areas and minimising condensation on the inside wall surfaces.

Slaked lime acts as the binder, basically holding the brick together, but it has other uses. On one side it protects against moisture by closing any pores and preventing the entry of water on external surfaces exposed to rain. On the other hand it provides a protection for the industrial hemp fibres against fungal and parasite attack.

The hemp bricks when laid endwise are used for the construction of external walls thirty centimeters thick. The internal walls built with hemp bricks are thinner being half the thickness. The delightful, popular cave homes of this area of Andalusia are naturally ecological in that they are re-developed from ancient derelict cave houses. Where ever possible the construction materials used are salvaged from derelict properties that have been demolished. This recycling minimises the environmental impact.

It is ironic that this area of Spain, the Altiplano, until the late nineteen sixties, was renown as an industrial hemp growing area. With the invention and development of nylon and related products, coupled with the end of the Franco area and farm mechanisation the basic agriculture of the area fell apart throwing huge numbers of people out of work. The population of many villages dropped by seventy five percent or more, most of the inhabitants migrating to the coast and major cities in search of work.

As a result of these traumatic changes in demographic the remaining population was mainly aged, the villages incomes dropped to near poverty level and many empty houses fell into disrepair.

Most of the land workers who moved away lived in cave houses which are now being revitalised by the growing demand for eco-properties.