Prediction of the performance of various strategies of subfloor ventilation as remedial action for radon problems.

In order to reduce the convective flow which is the principal responsible for the high indoor 222Rn concentrations, several mitigation technics have been developed and used in many countries. Since they don't always respond as expected, there is a need of instruments helping in their design and their evaluation. This paper suggests the use of a numerical code, based on the finite difference method, for the evaluation of 222Rn mitigation strategies in dwellings, It is supposed that 222Rn transport from soil into a dwelling occurs mainly by pressure-driven air-flow. The programme used calculates the pressure fields under the buildings, supposing a laminar air-flow in the soil and adopting the steady-state condition. Clear graphic outputs are delivered. The results of sample calculations are presented in order to illustrate the possibilities of the code. These calculations concern a house without basement, with an entry route for soil-gas : the floor-wall joint. A particular subslab depressurization system is included in the calculations. The code appears to be a powerful tool for the prediction and the evaluation of the performances of subfloor ventilation strategies.