Radon in housing companies
Radon in housing companies
There is as much radon on the ground floors of apartment buildings as there is in detached and terraced houses in the same area. High radon concentrations are detected in indoor air all the time, even in new residential buildings. In housing companies, it is recommended that radon measurements be conducted jointly so that potential radon mitigation can be planned in a centralized manner and carried out efficiently.
Radioactive radon gas originates from uranium in the soil. The uranium in the soil produces radon, which can enter residential buildings through the cracks in the base floor of the building. Depending on the number of the cracks and the pressure ratios in the building, radon concentrations may vary significantly from dwelling to dwelling. The greater the underpressure in a dwelling, the more likely it is that air containing radon enters the building from the soil.
In apartment buildings, radon may also find its way to upper-floor dwellings through intermediate floors, staircases and pipe shafts.
Exposure to radon in indoor air increases the risk of lung cancer especially among smokers. Each year, there are approximately 300 new cases of lung cancer in Finland that are related to radon exposure at home.
Reference value for the radon concentration
As of 1992, new dwellings must have been designed and built so that the radon concentration in the living areas does not exceed 200 Bq/m3. For older dwellings, the reference value in force is 300 Bq/m3.
Health-affecting conditions of dwellings, and consequently also the radon concentration, are supervised by municipal health protection authorities. On the basis of the Health Protection Act, a resident may request a municipal health protection authority to conduct an inspection in a dwelling. The health protection authority may order radon measurements to be conducted if there are well-founded grounds to believe that there is radon in the dwelling. In practice, there may be radon in all ground-floor dwellings and radon can only be detected by measuring it.
A housing company’s storage, recreational and sauna facilities are not dwellings so the reference value for dwellings is not applied to them. The housing company itself must decide what kinds of concentrations it considers acceptable in these facilities.
Measurement is easy and affordable: the price of one radon measurement box with associated analyses is EUR 40–60. A discount is given for ordering several boxes.
Measurement is conducted with a radon measurement box that is placed in the dwelling for a minimum of two months, preferably for three months. After the measurement, the box is sealed in an envelope and returned to the laboratory from which the box was ordered. After analysing the box, the laboratory informs the customer of the results.
In apartment buildings, most radon is found on the ground floor and on the lower floors. As a result, apartment building radon measurements are conducted in all dwellings that have wall or floor structures in contact with the ground. It is also recommended that measurements be conducted in dwellings on the first residential floor even if they have no structures in contact with the ground. Measurement should also be conducted in the shared recreational and sauna facilities located in the basement of the housing company. In terraced and detached houses, measurements are always conducted in all dwellings, at least on the ground floor.
If the area of the dwelling is less than 100 m2, one measurement box is enough. In larger dwellings, the use of two boxes is recommended. The boxes are placed in the living room or bedroom. If the dwelling has two floors, measurements are conducted on both floors.
Radon mitigation in apartment buildings and terraced houses is similar to that of detached houses. The most effective methods for radon mitigation are sub-slab suction and radon wells. Sub-slab suction creates underpressure in the soil under the building when compared to indoor air. This ensures that radon does not enter the building through the cracks in the base floor. A radon well is particularly well suited to buildings on moraines and sandy ridges.
Other means to reduce radon concentration in indoor air include ventilating the crawl space, sealing the base floor, improving ventilation and decreasing underpressure in the building.
Example of radon mitigation in an apartment building area
- There are 25 apartment buildings in the area.
- The soil is coarse gravel.
- The radon concentration exceeded 400 Bq/m3* in 24 ground-floor dwellings.
- The average radon concentration in the ground-floor dwellings was as high as 4,200 Bq/m3.
- A total of 23 radon wells were built at 3–7 metres from the buildings.
- After mitigation, the radon concentration in all dwellings was below 400 Bq/m3.
- The cost of one radon well is around EUR 3,000–5,000.
*During mitigation, the radon limit value according to law was 400 Bq/m3.