What technique is used to mitigate radon by depressurizing a block-wall foundation?

The technique referred to in the question for mitigating radon by depressurizing a block-wall foundation is indeed block-wall depressurization. This method specifically targets the reduction of radon gas entry into the living space by creating negative pressure within the block walls of a foundation. When the pressure inside the wall is lowered in comparison to the surrounding soil and atmosphere, radon gas is drawn away from the interior of the structure, effectively reducing its concentration inside.

The effectiveness of this method relies on adequately sealing any openings and ensuring that the air pressure differential is maintained, thus preventing radon from infiltrating. This specific technique is particularly useful in buildings with block-wall foundations that are prone to radon entry due to the natural passage of gas through the porous materials.

Other options may involve techniques for radon mitigation, but they do not address the specific mechanism of depressurizing block-wall foundations as directly or effectively as block-wall depressurization does. For example, perimeter channel draining and drain tile loops are generally associated with managing water drainages rather than directly targeting radon gas mitigation. Active soil depressurization, while related, typically refers to a more general approach that may not specifically address block walls and their unique characteristics.