Radon Map Ireland: EPA Risk Zones, Health Guidelines & Building Regulations

What is Radon Gas and What are the Health Risks?

Radon (specifically Radon-222) is an invisible, odourless, tasteless radioactive gas formed by the natural radioactive decay of uranium present in rocks and soils. When radon escapes from the ground into open air, it dilutes to harmless background levels.

However, when a house is constructed on radon-bearing ground, the building acts like a suction box. Slight indoor pressure differentials (caused by indoor heating and ventilation) draw radon gas into the living space through foundation cracks, cable service entries, unsealed cavity walls, and construction joints.

Once inhaled, radon decay products (alpha particles) irradiate delicate lung tissue, damaging DNA and significantly elevating the lifetime risk of developing lung cancer. The risk is magnified up to 25 times for smokers living in high-radon homes.

How the EPA Radon Map Classifies Irish Land

The EPA’s National Radon Map is based on geological mapping, soil permeability models, and historical measurements across hundreds of thousands of Irish homes. Land is grouped into three broad risk bands:

• High Radon Areas: 10km grid squares where statistical models predict that at least 10% of homes exceed the national indoor reference level of 200 Bq/m³. Counties with extensive high-radon clusters include Sligo, Galway, Clare, Kerry, Waterford, Carlow, Kilkenny, and parts of Wicklow.

• Moderate Radon Areas: 10km grid squares where between 5% and 10% of homes exceed the reference level.

• Low Radon Areas: 10km grid squares where fewer than 5% of homes exceed the reference level.

Crucially, the EPA emphasizes that high radon levels can occur in any individual home across ANY part of Ireland, even within low-risk grid squares, depending on local fault lines, granite gravel pockets, and foundation construction quality.

National Reference Level: The statutory reference level in Ireland is 200 Bq/m³ for domestic homes and 300 Bq/m³ for commercial workplaces, as set out in the Radiological Protection Act 1991 (Ionising Radiation) Regulations 2019.

Building Regulations TGD C Requirements for New Builds

Under Part C of the Irish Building Regulations (Site Preparation and Resistance to Moisture), builders and architects must adhere to strict radon protection details:

1. Low to Moderate Radon Areas: Every new dwelling constructed in Ireland must be equipped with a standby radon sump—a sub-floor perforated extraction pipe terminating in an accessible capped pipe outside the building wall. If subsequent testing reveals elevated radon, an electric extraction fan can be retrofitted without disrupting floors.

2. High Radon Areas: In addition to the standby sump, the builder must install a continuous, fully certified radon barrier membrane (minimum 300 to 400 microns, NSAI Agrément certified) beneath the concrete slab and across external cavity walls. All pipe penetrations, corners, and joints must be sealed with specialist radon-grade butyl tape.