Radon mitigation effects of passive stacks in residential new construction. Report for December 1989-February 1990

The paper discusses the effects of passive stacks in mitigating radon levels in residential new construction. Although passive stacks have been installed as a radon resistant measure in new houses, little quantitative data on their performance has been collected. The study involved continuously monitoring several houses that were recently built with radon resistant features including crack sealing, porous subslab aggregate, and a stubbed-off pipe penetrating the slab for installing a radon mitigation system. For the project, the piping systems were completed so that they exited the roof, and half the houses had radon mitigation fans installed in the piping. Houses were monitored continuously with the pipes sealed, then with the pipes open but no fans operating, and finally with the fans (if installed) operating. The results show significant radon mitigation effect by the passive stack systems in most houses. Failures of the passive stack systems appear to be due to basement depressurization by heating, ventilation, and air-conditioning (HVAC) duct leakage, poor installation of subslab piping, and poor communication between multilevel slabs.