Hemp: a still unknown insulation material. This less conventional material is recommended by professionals for its thermal and hydric regulation capacities, both for new constructions and renovations. Within the framework of the VLAIO-TETRA project led by the University of Hasselt in collaboration with the CTST and Pixii, research has been conducted on the hygrothermal properties of hemp. Discover in this article the different advantages of hemp blocks.

What are the hygrothermal properties of hemp ?

The hygrothermal properties are the characteristics that determine how heat, air and moisture move through hempcrete blocks walls. Good hygrothermal design is crucial to ensure the energy efficiency of the building, avoid moisture related problems and ensure a comfortable and healthy indoor climate.

Hemp and moisture management

As the University of Hasselt points out, hemp is a water vapor permeable material that acts as a water buffer, regulating moisture in the air. This means that sufficient moisture is easily stored in the material in the form of small water molecules.

Research also shows that hemp is highly hygroscopic due to its porous structure. This means that the material can absorb moisture from its environment, store it and release it again later. In practice, this means that if it is more humid inside the house, more moisture will be stored. If the interior is then drier, this moisture will be released back into the house. In this way, the material ensures a healthy indoor climate for the whole family.

Hemp and thermal regulation

Research from the University of Hasselt shows that the pores of hemp are also responsible for its insulating properties. The thermal conductivity of a material is expressed by its λ value, which indicates the amount of heat that passes through the material for a constant heat flow. The lower this value, the better the insulation. Compared to traditional insulation materials, hemp has a higher λ value, which means that a thicker layer must be placed to achieve the same thermal resistance. Nevertheless, hemp has a particularly high thermal inertia.

Thermal inertia has a direct impact on the indoor climate of a building. A wall with a high thermal inertia ensures that outdoor temperature peaks are only perceived later in the room (phase shift) and that outdoor temperature fluctuations are attenuated inside (attenuation). According to the University of Hasselt, hemp blocks offer a phase shift of up to 15 hours and an attenuation of up to 92%.

This allows hemp blocks to insulate in the following way: in winter, they give back the stored energy after turning off the heating. This limits the strong drops in temperature. In summer, on the other hand, they capture part of the excess energy. This way, you avoid overheating during hotter periods, and benefit from the restitution of this heat during cooler periods, such as at night. No need to heat your house all the time: you will save energy and money, while enjoying a comfortable atmosphere in any season.

A real advantage for your health

Moreover, IsoHemp hempcrete blocks are made from 100% natural and local raw materials, which prevent the formation of bacteria and offer you pure air to breathe. They will save you from allergies and respiratory diseases caused by petrochemical materials used on most construction sites. They offer a real benefit to your health and to the environment, thanks to a positive carbon footprint, and thus promote a better general well-being. The use of hemp blocks is therefore a worthwhile investment.

More information

The VLAIO-TETRA project

If you want to know more about hemp, its characteristics and its applications, discover the full report on the VLAIO-TETRA project (in Dutch)



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