Radon in the home: the invisible danger and how to protect yourself.

Radon precautionary areas are regions defined by law where, due to geological conditions, an elevated concentration of radon is expected in the soil air (GEO factor). Such designated areas exist in Germany, Austria and Switzerland (e.g. low mountain ranges). If your building is located in such an area, the requirements for radon protection are stricter, particularly for new buildings and workplaces. However, radon can also occur in unacceptable levels outside these areas. A measurement is the only way to be certain.

As radon escapes from the ground, basements and the ground floor are the most affected. It diffuses into the building through foundations, cracks in floor slabs, joints, cable penetrations or leaky basement walls. From there, it can also spread to upper floors via the ‘chimney effect’ (warm air rises).

The simplest and most reliable method is a long-term measurement using so-called passive dosimeters. These are small plastic containers which you place in the most frequently used rooms (e.g. living room, bedroom) and in the cellar for several months (ideally throughout the winter heating season). The results are analysed anonymously in an accredited specialist laboratory.

In Germany, the statutory reference value is 300 becquerels per cubic metre (Bq/m³) as an annual average for living spaces and workplaces. However, the World Health Organisation (WHO) recommends aiming for a target level of 100 Bq/m³ as a precautionary health measure. Any level below this further minimises the health risk.

Thorough airing helps to reduce the concentration temporarily. However, to keep radon levels below the reference value in the long term, ventilating by opening windows is too unreliable and inefficient. As soon as the windows are closed, the gas builds up again. Furthermore, in winter, a huge amount of heating energy is lost, which runs counter to the energy efficiency of modern buildings. Controlled ventilation is essential.

Modern or refurbished buildings are constructed to be airtight in order to save energy. However, without a controlled ventilation system, natural air exchange is prevented. Radioactive radon, which enters unnoticed, can no longer escape and accumulates in living spaces – airtight houses trap the hazard.

Our decentralised ventilation systems operate in balanced mode (cross-ventilation). They are designed to precisely balance the volumes of supply and extract air. This prevents a permanent negative pressure from developing in the living space, which, like a vacuum cleaner, would draw additional radon from the cellar or the ground into the house. A slight positive pressure in the cellar area is actually beneficial.

Yes, absolutely. Cellars are the main entry points. Controlled, decentralised cellar ventilation with heat recovery is a very effective measure that is easy to retrofit. It dilutes the gas directly at the source and extracts it before it spreads throughout the rest of the house. It also protects the basement from damp and mould.

Our modern LUNOS control systems can be fitted with sensors (e.g. CO₂ or humidity sensors). These monitor air quality indirectly. Although they do not measure radon directly, demand-controlled ventilation – which responds to the presence of people or humidity – automatically ensures increased air exchange when the air is ‘stale’. This helps to regulate radon concentrations reliably, even without a dedicated radon sensor.