There are a number of remediation measures that reduce elevated radon concentrations in buildings. If the radon concentration in a building is above the reference value of 300 Bq/m³, this can be remedied by tried and tested remediation measures on the building.

The measures range from sealing building components to extracting soil gas from underneath the building. Before starting remediation, detailed radon measurements can be useful as a basis for remediation planning by a specialist. One or more remediation methods are then determined. In the case of very high radon concentrations, immediate measures must be implemented.

After remediation, the success must be checked by means of a radon measurement. If the radon value is still above the reference value, further remediation measures must be taken. The functionality of the measures (no blocked pipes, functioning fans, etc.) must be checked regularly.

The implementation of radon remediation measures to reduce radon concentrations in buildings in Austria is described in ÖNORM S 5280 Radon - Part 3: Remediation measures for buildings.

The techniques recommended in the ÖNORM for radon remediation of buildings are largely based on the experience gained from national radon programs in Austria, the USA, Canada, Sweden, Finland, Great Britain, Switzerland, South Tyrol and Germany.

A distinction is made between the following radon remediation measures:

• Subsoil extraction (UBA)

In existing buildings, subsoil extraction is usually carried out in the form of radon wells, but can also be carried out over a large area using radon drainage. The radon-containing soil air is extracted either actively using fans or passively via the roof using the thermal effect (chimney effect).

• Generation of overpressure in the building (basement) (EÜG)

By blowing in low-radon outside air using wall or ceiling fans - if necessary with heat recovery - an overpressure of a few pascals is generated in the affected rooms in the building. This remediation method can only be used where the affected areas/rooms are sufficiently tightly sealed to the inside and outside (otherwise no overpressure is possible in the room).

• Increased floor ventilation below the floor slab (BB)

The increased floor ventilation takes place below the building in a highly permeable intermediate space, e.g. ballast box or crawl space. Air must not be allowed to flow from the intermediate space to the occupied rooms directly above. There must be sufficient thermal separation from the occupied rooms above (prevent the floor area from cooling down).

• Intermediate floor extraction (ZBA)

An additional continuous cavity (intermediate floor) is created between the original interior floor. A fan is used to create a slight negative pressure in the created cavity and thus the radon-containing air from the cavity is led outside.

• Reduction of the negative pressure in the building (due to the chimney effect) (RUG)

This method is used as an additional measure to reduce radon ingress into the building. The following must be observed here:

- Avoidance of exhaust air fans inside the building
- Installation of a fresh air supply duct, e.g. when operating an open fireplace
- Prevention of air movement between individual storeys, e.g. by means of sealed doors

• Prevention of convective air flow between the basement and rooms above (UKL)

This method is used as an additional measure to reduce radon ingress into the building. Simple sealing of openings and shafts, for example, is required to prevent the flow of air from an existing cellar towards the occupied rooms of the building.

• Sealing of openings, cracks and crevices or sealing of surfaces or coatings (VV)

This method is used as an additional measure to reduce radon ingress into the building. Obvious openings in walls and floors must be sealed with a suitable sealant, cracks and fissures must be sealed.

• Shielding the subsurface with injection screens (INJ)

A sealant injected over a large area forms a tight layer between the building component and the ground, which can reduce radon ingress.

After remediation, the success must be checked by means of a radon measurement. If the radon value is still above the reference value, further remediation measures must be taken. The functionality of the measures (no blocked pipes, functioning fans, etc.) must be checked regularly.

After remediation, a radon measurement must be carried out in accordance with the Radon Protection Ordinance. An indicative short-term measurement (usually during the heating period) can be carried out for an initial assessment of the effectiveness of the radon remediation measures.

In renovated private households, a new radon measurement is recommended every 10 years (in the radon precaution area) or every 5 years (in the radon protection area). The requirements in accordance with the Radiation Protection Act and Radon Protection Ordinance apply to mandatory workplaces.

Simple radon remediation in residential buildings with one or two residential units is possible for as little as a few hundred euros. For more complex remediation measures, total costs of around 2,000 to 15,000 euros can be expected.

The federal states Upper Austria, Styria andTyrol promote structural remediation in the event of high radon concentrations.

Experts are available to assist you with the planning and implementation of structural radon protection measures.