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How CN Construct expanded clay serves to not only lower radon exposure in buildings, but also prevent it

Radon is a radioactive noble gas that can cause lung cancer. A European directive stipulates that people must be protected against excessively high radon concentrations in buildings. Since February 2018, this Radiation Protection Ordinance is also in force in Germany. An insulating layer of CN Construct expanded clay under the foundation, in combination with simple ventilation systems, offers developers and architects a reliable solution already today.

Radon is odourless and colourless and occurs all around the world in the ground. From there it can penetrate buildings. The primary points of entry are foundations, basement walls and building walls. The concentration first rises through cracks, gaps, joints or leaky conduits into basement spaces and then spreads throughout the building, so that the room air is constantly contaminated.


The World Health Organization (WHO) classified radon as carcinogenic already in 1980. It is undisputed that long-term exposure to radon in rooms significantly increases the risk of contracting lung cancer. With approx. 2,000 cases per year in Germany, radon is the most frequent cause of lung cancer in non-smokers.

The new Radiation Protection Ordinance, which entered into force in February 2018, provides that radon concentrations in buildings shall not exceed 300 Becquerel per cubic metre of room air. To further minimise the health risk, a value of less than 100 Becquerel is desirable. In new buildings, it is therefore important to take preventative measures to prevent radon from penetrating into buildings from the outset.

Expanded clay protects buildings against radon gas

By virtue of the low density within a layer spread under the building, the specially treated expanded clay in the 10 - 20 mm particle size ensures that radioactive gas can collect under the foundation and is not immediately pressed into the building. The gas is then released from the expanded clay layer to the outdoors, where a hazardous concentration is quickly diluted to a non-hazardous one. The gas is discharged using the chimney effect of pipe systems, which can also be solved by design means through the chimney. However, CN Construct expanded clay impresses architects and building owners in many ways. It also functions as an insulating layer which helps to conserve energy and as a reliable drainage to guard against and dissipate excess moisture.

We will be happy to advise you personally about applications or particle sizes and can supply the product to you in expedient units from bags to entire vehicle loads.

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