Measures to provide protection against radon

Radon protection by baseplate sealing and low pressure in the foundation using radon drainage

The naturally occurring radioactive noble gas radon passes from the geological underground into buildings, if these are not dense in the ground touching area. The average annual radon concentration in residential areas in Germany amounts to 50 becquerels per cubic meter of room air. In areas with higher radon concentrations in the soil air and good transport routes for radon, increased radon concentrations in buildings are more common. However, annual mean values ​​of more than 1,000 becquerels per cubic meter are rare.

People considering the refurbishment of a building should evaluate the possible health risk beforehand. The basis for this is the annual mean value of the radon concentration in rooms that are used frequently (such as the living room, the sleeping room, or the nursery). Measurements which are performed only once have only limited informational value here. Depending on how often and how long people air their rooms, the concentration of the gas changes. Since people air their rooms more frequently in the warmer seasons and, thus, there is a higher exchange of indoor air, the mean radon concentrations are lower at these times.

National and international research has shown that there is an increased risk of approximately 10 per cent per 100 becquerel per cubic metre compartment air, of contracting lung cancer. Those who stay over many years in rooms where concentrations around 1,000 becquerel per cubic metre are measured, have a risk of contracting lung cancer that is twice as high, compared to the risk of persons staying in rooms with an annual mean value around 100 becquerel per cubic metre. Therefore, it is advisable to refurbish buildings with a radon exposure which exceeds 100 becquerel per cubic metre.

The Federal Office for Radiation Protection (BfS) provides further information about health effects of radon in appartments.

Where and when are refurbishment measures reasonable?

Radon is a gas generating in the soil. Therefore, potential spots where the radon can get into the building are mostly to be found in areas of the building that have contact to the soil, such as house walls, foundation, or cellar. Through cracks, gaps, or pipe penetrations, the gas finds its way to the interior of the building. However, radon also gets into the house from the external air, and even construction materials release the gas.

At a radon concentration of more than 100 becquerel per cubic metre, the radon, that sneaks in from the underground, prevails. In cases like this, refurbishment measures are reasonable. Often, simple measures are already sufficient, such as

• Frequent, intensive airing,
• Sealing of cracks, gaps, and pipe penetrations in areas of the house touching the soil,
• Sealing of doors and pipe penetrations between cellar and upper floors.

As radiation exposure does not only depend on the radon concentration in the ambient air but also on the length of time persons stay in rooms, it may be another point to change the usage of the room.

How rapidly refurbishment work should be carried out depends on the annual mean value. The recommended period up to refurbishment depends on the level of radon concentration. At compartment air concentrations higher than 1,000 becquerel per cubic metre, measures should be completed within 3 years.

Before a building is refurbished, an expert should first determine the causes of the elevated values and evaluate the constructional situation. Taking into account the effort and prospects of success, different refurbishment options are be weighed against each other. In general, it should be said that the higher the radon concentration is, the more efficient a refurbishment measure should be.

People planning renovation and extension work should pay attention to them during refurbishment work and, if possible, take them into account. After refurbishment has been completed, it is recommended to evaluate the success of the measures through measurements. Here you will find a list of testing laboratories providing passive measuring devices and quality assured evaluations.

What should be considered when building a new house?

New buildings should be planned in such a way that average radon concentrations in living space exceeding 100 becquerel per cubic metre per year are avoided. In most cases, the construction measures that are used according to today’s state-of-the-art of technology, are sufficient, that is, mainly the correctly insulation of walls touching the soil and of the foundation from soil humidity. Radon-tight construction materials and thorough construction work provide additional protection. Facilities for the dissipation of radon-containing air from the ground are often used, too.

For areas with elevated radon concentration in the soil air or very permeable building ground, special techniques have been developed and tested. In such cases, the radon concentration in the soil air should be measured first. Subsequently, appropriate measures can be selected to seal the construction against radon.

German handbook on Radon

For the German Handbook on Radon, the BfS has compiled detailed informations regarding the design of radon mitigation measures. If you are interested in purchasing a copy (in German), please send an e-mail to info@bfs.de.