The Effect of Rain and Hvac Setting on Radon Levels in a Home

This study sought to determine the effect of environmental conditions on radon levels in a home. The two independent variables in the experiment were (1) whether or not it was raining and (2) whether the HVAC system on the main level of the home was set to “ON” for continuous ventilation or “AUTO” for forced air only to maintain temperature. A recently calibrated Radalink AirCat® radon detector was placed in an unfinished basement of a three story house that had recently recorded concentrations at 4.0 pCi/l, the action threshold level. Based on the results it was concluded that an active ventilation system successfully reduces radon. For this particular house, it was also concluded that the presence of rain increases radon concentration levels. The absence of requirements for engineered ventilation in our residential building codes misses the opportunity to achieve safer levels. Accordingly, regulatory measures are recommended for new residential construction. Introduction Radon penetrates homes through walls, floors, foundations, and pipes. Radon is the second leading cause of lung cancer, causing 21,000 deaths per year in the United States and many professionals estimate that a reduction of levels to below 2.0 pCi/L nationwide would likely reduce the annual lung cancer deaths attributed to radon by 50% (EPA, 2013). Therefore, even though radon concentrations below 4.0pCi/l are acceptable, for health considerations, lower radon exposure levels would be even safer. Background Many factors influence the laws governing radon levels in residential structures. Ensuring public safety is balanced with various financial considerations. For example, in home re-sale situations, the presence of high levels of radon during the inspection could either cost the seller significant radon mitigation costs or perhaps cancel the contractual offer. For new home sales, builders who expect testing below the 4.0 pCi/l threshold in a new neighborhood will unlikely employ mitigation techniques which could reduce radon levels even more. This misses the opportunity to make our homes even safer at a time during new construction when it is much less expensive to implement and less invasive to the homeowner. One of the most fundamental factors affecting radon levels is the negative pressure differential of the air on the ground floor of a home relative to that of the underlying soil. Higher differentials result in more radon being pulled to the surface and into the home via the so-called “stack effect.” Various factors can influence this pressure differential and overall detected radon levels. Even within a given testing period, large fluctuations typically occur and are even expected.