The principal building material used to construct the external walls of an eco cave house will consist of an eco-brick, manufactured in nearby Guadix with the proprietary name of Cannabric®.
Cannabric is an eco-brick that derives its properties from industrial hemp fibres (cañamo). The eco-brick is composed of industrial hemp, natural slaked lime and a mixture of minerals. Cannabric combines 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 Cannabric the ideal choice in areas of southern
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 the 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 Cannabric allows 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.
The use of slaked lime as a binder has many 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.
