Use and development of waterproofing products in the construction industry to retain radon released from soil and building materials

Indoor radon is classified as a carcinogen because it can lead to lung cancer. Mitigation strategies based on protecting buildings with radon barrier materials, home ventilation, or room pressurization are regularly used. The main radon sources are soil and building materials. Radon can accumulate indoors seeping through cracks in foundations or walls, and gaps around service pipes or electrical outlets. Different types of waterproofing materials were tested to determine their performance as anti-radon membranes, with the final aim of applying them in real cases and reducing health risks. Therefore, two different approaches were used: the scale model room for defining the relative reduction of indoor radon, and the TESTMAT device for determining the radon diffusion coefficients. Both experimental devices and configurations are original and designed specifically for this research project. The scale model room made from a porous ignimbrite rich in radon precursors was used as an analogue to test the efficiency of twenty-seven airtight membranes to reduce radon levels, also in combination with room pressurization. Relative reduction of Indoor Radon ranges from -20 to -94%. The introduction of room pressurization further reduces radon levels in the model room where the membranes were applied. The TESTMAT uses a non-stationary radon source and follows the approach A of ISO/TS 1165-13 based on the Explicit Finite Difference Method (EFDM). The formulas and the procedure are enveloped in a specific software, called ENDORSE, elaborated for this device. The system was first calibrated and then tested with three membranes, and results show that they are good barriers to protect the building in line with the expectations set forth in the literature. Surveys on indoor radon were conducted in two homes in the Lazio region, Central Italy. The buildings were examined because they had average indoor radon values higher than the reference value of 300 Bq m-3. The two houses are built on volcanic terrains, with a high/medium GRP for the municipality of Celleno, the first case study, and a low/medium GRP for Monte Porzio Catone, the second. Furthermore, the two dwellings are made completely or partly of volcanic materials (tuff). The application of a good anti-radon membrane in Celleno’s house showed a substantial gas reduction in a room during the monitoring. Each case study is complex due to the simultaneous interplay of many factors affecting the radon entry into a building, therefore a conceptual model is useful to identify the prevailing radon source, also considering the building's structural characteristics, the geological and topographical setting, the influences of the meteorological variables, as well as the living habits of tenants. In Celleno’s case study, it was possible to harness the wind effects, including its directionality and intensity, to reduce radon concentrations in the pilot room. The wind naturally ventilated the semi-basement cavity, which acted as a radon accumulation chamber. In Monte Porzio Catone’s case study, however, the effect of the wind had an opposite role. Its impact on the exposed side, where the cavity was underground, increased the radon suction from the ground.