CH2M Hill Engineering Ltd
Bibliographic info:
Canada Mortgage and Housing Corporation, May 1995

Remedial measures to prevent soil gas infiltration have been implemented on many buildings affected by intrusion of radon, water vapour, methane and other volatile organic compounds (VOCs ). The success of these measures has been well documented for gases such as radon; however similar detailed documentation was not readily available for methane or other vocs. The objective of this study was to evaluate the effectiveness of four different remedial solutions installed on houses. All houses tested in this study had the potential of methane intrusion. Nine houses were tested as part of this study. The four different remedial measures which were evaluated included: a liner with a subslab passive vent system; an active venting fan connected to a foundation perimeter gas collection pipe; a passive vent connected to a foundation perimeter gas collection pipe; and a liner system only. Each of these four systems were installed in four separate communities across Canada. Based on long-term monitoring, none of the nine houses tested were identified as having significant methane concentrations indoors due to soil gas entry. Although the remedial measures installed may have had an effect on the limited amount of methane detected indoors, other factors such as low methane generation rates, and diffusion controlled sources also had significant influence. In fact, at some houses, the control systems likely were not necessary because of these factors. Further short-term tracer tests were carried out on one of the systems to evaluate the integrity of the remedial measure. Based on a limited number of houses tested, the results suggested that the amount of gas could be limited by as much as four orders of magnitude.