The effectiveness of passive sumps and static cowls in reducing radon levels in new build Irish dwellings.

The most cost-effective way of protecting the population from radon is to ensure that new dwellings are built to prevent the entry of this gas from the ground below the building. One of the most common methods used to protect buildings from radon is the installation of a system to depressurize the subsoil below the building, reducing the ingress of the gas indoors. Laboratory based research has shown that the use of a wind-driven passive radon sump and static cowl has significant potential to protect new buildings in Ireland through depressurization. A field trial of this system was carried out in a sample of new Irish dwellings built to the requirements of Irish Building Regulations. The study focused on six unoccupied, adjacent, south-east facing dwellings of identical construction. The variables of occupancy, geology, building type, building material and weather were all controlled for, consequently, the study was carried out under highly controlled conditions. The radon levels in each of the dwellings were measured over a 6-week period under three test conditions: the passive sump closed, the passive sump open and the passive sump open with a static cowl installed. The results show an average reduction of 65% in radon levels due to the installation of a wind-driven passive sump. The cumulative effect of the installation of a passive sump plus a static cowl was an average reduction in radon levels of 75%. The number of observations that exceed the Government's Reference Level for dwellings of 200 Bq/m was reduced from 38% with the passive sump closed to 9% when the passive radon sump was in operation and 0% when both the passive radon sump and static cowl were installed. These results are statistically significant, and the cost is estimated at €100 per dwelling. The study concludes that the installation of a passive sump fitted with a static cowl in new dwellings is a low cost, effective method of reducing radon exposure in new Irish dwellings.