Sub-slab depressurisation systems used in the Czech Republic and verification of their efficiency.

Design principles for sub-slab depressurisation systems recently used in the Czech Republic for remediating existing buildings are described. Results of an efficiency analysis performed on the basis of data from >60 single-family houses are presented. It was found out that the efficiency varies between 70 and 98 %, which is twice greater than when additionally applied radon-proof insulation is used. The efficiency is mainly influenced by the vertical profile of the soil permeability and by the air-tightness of floors resting on the soil. Higher efficiency was found for houses with greater air-tightness of the floors and with a sub-floor layer with permeability higher than the permeability of the subsoil.