How to read the radon map
The EPA's map gives each area a predicted share of homes with radon above the national reference level of 200 becquerels per cubic metre (Bq/m³):
| Map category | InSite label | High Radon Area? |
|---|---|---|
| 1 in 5 homes or more above the reference level | High | Yes |
| 1 in 10 homes | Medium | Yes |
| 1 in 20 homes | Low | No |
A High Radon Area is anywhere where 10% or more of homes are predicted to be above the reference level, so both the 1-in-5 and 1-in-10 areas count. Large parts of the west and south, and areas over granite and some limestones and shales, are higher risk.
What it means for a site
- New builds: Building Regulations Technical Guidance Document C sets out radon protection. All new homes in a High Radon Area must have a radon membrane; check the current TGD C for the full requirements (including radon sumps) that apply to every new building.
- Existing homes: the map is a prediction for the area, not a measurement of a house. The only way to know is a radon test, which is cheap and takes three months. If a house is above the reference level, fixes such as a sump and fan usually work well.
- Workplaces: employers in High Radon Areas have to test ground-floor and basement workplaces.
What it can't tell you
- Radon varies house by house, even next door. A Low area can still have high-radon homes; testing is the only answer for a particular building.
Sources
- EPA radon risk map of Ireland, epa.ie/radiation/radonmap
- Building Regulations, Technical Guidance Document C
Last reviewed 2026-10-02.