In the UK, homeowners usually carry out radon testing using two passive detectors, one of which is placed in a living room and one in a bedroom. If the radon test results show elevated levels are present, these results are then presented to the radon mitigation specialist to use as a basis for designing a remediation system.
In many instances, homes have a footprint that is a lot larger than a single room, therefore the radon levels throughout the ground floor can differ considerably. Other properties may have been extended, with different areas having differing floor constructions.
Designing a mitigation system on the basis of only one or two radon measurements can therefore present a conundrum, as it is unlikely that the contractor will be able to identify a) whether there is a particular point of radon intrusion or b) whether a mitigation system needs to address the entire footprint of the property.
propertECO use a RadStar GM1-2 to carry out diagnostic profiling of radon levels at the design survey. The GM1-2 allows a series of short (six minute) grab sample radon measurements to be taken. The purpose of this grab sampling isn’t to find out what the radon level within the property is, as radon levels fluctuate from day to day and long term measurement is required for this purpose. The short term measurements allow a pattern of comparable readings to be created, to diagnose whether there are similar radon concentrations throughout the entire ground floor or, for example, if there is a particular ‘hot spot’ in one area which is likely to be the source of radon ingress into the building.
This profiling exercise enables us to design a radon mitigation system with greater confidence than simply relying on two long-term measurements. The pattern of profile readings provides guidance as to where the optimum location for installing a radon sump system will be as well as highlighting any possible entry points due to defects in the construction itself, which can be easily remedied. This can often mean cost savings for the client in the long run.
Case Study
A client asked us to design a mitigation system after receiving radon readings of 480 Bq/m3 in the ground floor living room and 360 Bq/m3 in the principal first floor bedroom. Profiling was carried out using the RadStar GM1-2 and revealed that peak radon intrusion was occurring via an under-stairs cupboard, which had an unfinished floor. This area would never routinely have been tested, however discovering that this was the main route of entry of radon into the building (and from where a pathway upstairs was originating) meant that we knew our mitigation system should be focused in this part of the property.
A dual-spur mini sump system was designed, with the main collection area beneath the under-stairs cupboard.
Repeat radon monitoring using passive detectors was carried out over 12 weeks, commencing one month after completion of the works. The results showed that the radon concentration in the living room had fallen to 5 Bq/m3 with the same level reported at first floor level.
