The radioactive gas radon and its decay products have long been known to cause lung cancer. As early as 1567, Paracelsus described "Bergsucht" (later called "Schneeberger Krankheit"), a disease of the respiratory tract that occurs particularly among miners in the Erzgebirge. It is now known that high exposure to radon and its decay products was the cause of the disease.

The concentration of radon in the air is given in the unit Bq/m³. 1 Bq/m³ means one radioactive decay process per second in one cubic meter of air. In the meantime, a number of worldwide studies have shown that radon is the second most common cause of lung cancer after smoking. These studies suggest that there is no threshold value for the risk of developing lung cancer with regard to radon concentration in indoor air. The World Health Organization (WHO) therefore recommends limiting indoor radon concentrations to 100 Bq/m³, or - if this is not achievable - to 300 Bq/m³. In the EU basic standard 2013/59/EURATOM of 05.12.2013, a reference value of 300 Bq/m³ is specified for recreation rooms and workrooms, which should not be exceeded and, if possible, undercut. The new German Radiation Protection Act (coming into force 31.12.2018) and the Radiation Protection Ordinance of the Federal Republic of Germany adopt the reference value of 300 Bq/m³. Thus, radon protection and the resulting requirements have also arrived in the construction sector. For planners, building contractors and experts, dealing with structural radon protection begins at the moment when they design, plan, carry out or accompany construction work on existing buildings.

While structural radon protection can be implemented relatively unproblematically in new buildings by means of an air- or gastight design of the building envelope in contact with the ground, the solutions in existing buildings are considerably more complex and costly. Especially in older buildings, the building envelope in contact with the ground is usually not airtight and the required airtightness cannot be achieved with reasonable effort. Other solutions must therefore be applied here, which require extensive preliminary investigations as well as detailed planning and construction supervision.  This results in extensive cooperation and consulting obligations as well as liability risks for the persons acting on the construction site.

With the reduction of the air permeability of the building envelope, which is the inevitable consequence of every professionally carried out energy-related refurbishment measure, the natural discharge of radon from the buildings into the open air is also reduced. The radon concentration in the indoor air can thus increase significantly and in unfavourable cases reach a multiple of the previously existing concentration.

Due to the special features and special requirements for structural radon protection in existing buildings, the WTA working group "Radon in existing buildings" was established.

The objective of the working group is to develop a WTA leaflet that will provide building professionals with a guideline for dealing with radon in existing buildings. The content of the leaflet will be basic statements on radon entry and radon distribution in buildings, on the measurement of radon concentration and on radon protection measures, taking into account the structural conditions and - if necessary - requirements of monument conservation.

A guideline in a format adapted to the international orientation of the WTA is planned, with a core area that summarises the generally valid findings independent of national regulations, and national appendices that contain the country-specific regulations and are updated at national level. Provided that the hoped-for and desired international participation takes place, the information sheet will be prepared and published in English.

For any questions, please contact Ms Schneider in the office or Marc Ellinger.