Sub-slab suction system design for low permeability soils

Soils having permeabilities in the range of 10-11-10-10 m2 have sometimes proven to be difficult subjects for the successful implementation of radon-mitigating sub-slab suction systems. The characteristics of soils having permeabilities in this range have been studied and a model developed that describes the pressure fields and airflows that may be expected due to sub-slab suction points. The model has been computerized to permit its use as a design tool for a variety of slab and sub-slab suction system configurations. In this paper, methods of using this model to help optimize sub-slab suction system design and the effectiveness of mitigation are presented. Pressure-field and airflow predictions that have been made using this technique, as well as the resulting decreases in indoor radon concentrations, are compared with measurements made on the University of Florida Test Slabs and for whole-house installations