PERFORMANCE OF RADON CONTROL-SYSTEMS

Of five types of radon control techniques installed in seven New Jersey houses with basements, systems based on subsurface ventilation (SSV) by depressurization were the most effective and suitable for the long-term reduction of indoor radon levels. Small seasonal variations in substructure radon levels were observed in several houses while SSV systems were operating and may be due, in part, to changes in substructure ventilation rates from below 0.2 h-1 to approximately 0.4 h-1. Effective permeabilities for near-house materials measured at SSV pipes were an order of magnitude larger (geometric mean (GM) of 4.1 X 10(-9) m2) than the permeabilities of surrounding soils (GM of 1.5 X 10(-10) m2). Below-grade substructure surfaces appeared to have large air leakage areas as indicated by high entrainment fractions (0.41-0.92) of basement air in SSV exhausts. These leakage areas probably increased the effective permeabilities and influenced SSV flows and pressure field extensions. By sealing accessible leakage openings, greater depressurization below the slab during SSV operation was achieved in several houses, although indoor radon levels were not affected. In two houses, heating and cooling air distribution equipment caused additional substructure depressurizations ranging from 1.1 Pa to 5.4 Pa, but did not compromise radon reduction by SSV systems. Installation costs for SSV systems averaged $2270, while estimated annual energy costs to operate fan-driven radon control systems ranged from $85 for houses with oil heating to $250 for electrically heated houses.