Radon mitigation aims to ensure the lowest possible radon concentration that can be achieved with practical measures. Before radon mitigation, a two-month radon level measurement should be conducted in the measurement season September-May.
Houses built in the 2000s often have radon piping that was installed under the floor slab during construction. If the radon concentration in living areas exceeds 200 Bq/m3, the radon piping is activated by leading its exhaust duct through the roof (if this was not done during construction) and by connecting an extractor to the exhaust duct.
If there is no radon piping under the floor slab, radon concentration can be reduced by installing sub-slab suction. An alternative method is a radon well built outside the house, a few metres from the foundation. This solution, however, is suitable only for houses built on coarse sand or gravel. These are the primary methods if the radon concentration exceeds 300 Bq/m3. If the radon concentration is between 200–300 Bq/m3, suitable easy-to-implement measures should be considered, such as improvement of poorly functioning ventilation and sealing of clearly identified leaks.
The mitigation method depends on the measured radon concentration, the soil under the building, the backfill, the structures of the house and the ventilation system. The average radon mitigation costs in Finnish low-rise residential buildings are estimated at EUR 2,300 per dwelling unit.
The outcome of the mitigation measures should be checked by conducting a two-month measurement in the measurement season.
Mitigation guide: Asuntojen radonkorjaaminen. (Indoor radon mitigation.) STUK-A252.
The most efficient radon mitigation measures aim for reduction of radon-bearing air flow into the house. This can be carried out with sub-slab suction or a radon well. Sealing of leakage routes may also be possible. Ventilation-based measures may also reduce the radon concentration. The same methods are used for radon mitigation in blocks of flats and low-rise residential buildings.
|Mitigation method||Reduction of radon concentration, %|
|Crawl space ventilation||30–80|
|Improvement of ventilation in cellar||20–60|
|Improvement of efficiency of ventilation||10–50|
|New exhaust air ventilation system||10–40|
|Replacement of supply/exhaust air system||20–50|
|Sealing of leaks, wooden walls||10–35|
|Sealing of leaks, concrete element walls||30–55|
|Sealing of leaks, blocks of flats||30–65|
Tax credit for domestic costs
Costs incurred from radon mitigation entitle to tax credit for costs of the work. For more information, see the instructions issued by the Finnish Tax Administration (www.vero.fi).