What factor typically has the greatest impact on the complexity of a mitigation system?

The complexity of a mitigation system is heavily influenced by the characteristics of the building's foundation. A foundation that is deep, dense, or constructed with materials that have high radon permeability can significantly complicate the design and implementation of radon mitigation strategies. Factors such as whether the foundation is a slab, crawl space, or basement must be considered, as these structures dictate how radon enters the dwelling and how exhaust systems can be implemented effectively.

For example, in a building with a shallow foundation or one that is built on a type of soil that drains well, mitigation may be simpler since the radon pathways are more straightforward and can be easily sealed. Conversely, a complex foundation may require advanced techniques, such as sub-slab depressurization or active soil depressurization, to effectively reduce radon levels.

Other factors such as the climate of the region, the age of the building, and the size of the dwelling do have an impact on the overall mitigation process, but none usually supersede the foundational complexities when it comes to the challenges posed in effectively mitigating radon. The foundation dictates the initial entry points for radon gas and thus has the most substantial bearing on how mitigation efforts are strategized and executed.