Where must membranes for sub-membrane depressurization systems be sealed?

The correct answer focuses on the importance of sealing the membranes to effectively resist air movement between the soil and the air above the membrane. In sub-membrane depressurization systems, the primary purpose of the membrane is to create a barrier that prevents radon and other soil gases from infiltrating a building.

By sealing the membrane properly, it ensures that these harmful gases cannot migrate from the ground into the living spaces. If the membrane is not sealed adequately, there could be pathways allowing for gas entry, which would undermine the effectiveness of the mitigation system. Thus, robust sealing around the entire perimeter and any openings is critical for the performance of the system.

The focus on just specific areas like the top or bottom edges, seams, or just one part neglects the comprehensive barrier function required for maximizing the system’s efficiency and reducing the risk of gas intrusion.