What structural feature is associated with lower rates of radon entry?

Pier foundations have lower rates of radon entry primarily because they create a space between the ground and the structure, allowing for ventilation and minimizing direct contact with radon-containing soil. This elevation reduces the risk of radon gas accumulating in enclosed spaces. Since radon is a decay product of uranium and is found in soil, having a foundation type that allows for airflow helps disperse any radon gas that may be present in the soil below.

In contrast, basement foundations can trap radon gas as they are in contact with the ground, providing direct pathways for radon to enter the home. Concrete slabs may also allow some radon to seep through cracks or gaps in the slab, while wooden foundations do not necessarily provide any specific benefits against radon entry and may still experience the effects of radon infiltration from the soil below. Overall, the design of pier foundations offers a significant barrier against radon entry, making them more favorable in mitigating radon exposure.