Effectiveness of secondary radon protection in Northamptonshire houses

Northamptonshire is classified as a radon affected area, with greater than 1 per cent of houses being above the UK action level of 200Bq/m^–3. New houses, in areas where >10 per cent are above the action level, have to have primary protection of a radon‐proof membrane and secondary measures such as a non‐activated radon sump. New houses, in areas where 3‐10 per cent are above the action level only need the secondary measures. This research calls into question the effectiveness of this strategy. The use of radon potential maps, rather than radon in building maps, would have demonstrated that radon “hot spots”, where a very high percentage of houses are over the action level, can occur on a range of geology. One estate, at Higham Ferrers, had 35 per cent over the action level, even though it had been classified as only requiring secondary measures. The reluctance of occupiers in the UK to instigate monitoring and remediation means that very few will have their house tested for radon and activate the sump, by fitting a fan, if that is required. This paper provides arguments that support the view that it would be more effective to have primary and secondary measures introduced in all new houses in radon affected areas.