Since 2011, the National Research Council of Canada (NRC) and Health Canada’s National Radon Program have been working on a multi-year study to develop safe and cost-effective solutions to minimize the health risks from radon gas exposure in Canadian homes and to provide guidance for radon prevention and mitigation.
The intent is to:
- support the National Building Code’s (NBC) standing committee to address proposed changes to the NBC,
- provide input for updating guidance documents to be adopted as standards, such as the Canadian General Standards Boards National Standards for Radon mitigation options for existing low-rise residential buildings,
- and help verified technologies and products to access market and benefit the health of Canadians.
In response to Canadian regulator, manufacturer, builder and homeowner requests, the NRC’s radon team led by Research Officer Liang (Grace) Zhou, has been conducting experimental studies in occupied homes, research houses, the Radon Infiltration Building Envelope Test System, and the Radon Diffusion Test Chamber (RDTC) to answer key questions in relation to alternative approaches to control radon in Canadian homes. Those questions are:
Can full-size passive radon stacks in Canadian homes control radon in the habitable space, maintain negative pressure in sub-slab areas, and create sufficient chimney effect in the stacks?
Since December 2014, British Columbia’s provincial building code for Zone 1 radon-prone areas have required the installation of a full-size vertical passive radon stack extending upwards through the building and terminating above the roofline. In 2014 and 2015, the NBC standing committee on housing and small buildings received two building code change requests to include such stacks in the NBC. To help the standing committee address this change request, NRC’s radon research team completed a field study of extended passive radon stacks in 4 homes in the National Capital Region. The study compared the results of measurements made with the operational passive radon stacks (open stacks) for a period of 30 successive days or longer with the results of measurements made with the non-operational stacks (closed stacks) for a period of 30 successive days or longer.
The first series of open and closed stack tests took place during the fall and the early winter of 2017, and the same tests were repeated during winter 2017 to spring 2018. Under the test conditions, the passive radon stacks in the 4 study homes reduced the indoor radon concentrations by 37%, 90%, 85%, and 52%, respectively. The radon reduction appeared to be positively correlated to the height of the stack.
In this study, the portion of the stack in the unheated attic space was insulated by using a fibre glass duct sleeve to achieve R7 insulation factor (R-value of 7 K•m²/W). The portion of the stack above the roof was insulated by spray foam to achieve R14 insulation factor (R-value of 14 K•m²/W). The research team believed the insulation has enhanced the stack effect and contributed to the greater radon reduction. Starting November 2018, NRC’s radon research team has started another field study of passive radon stack in 15 homes in Prince George, British Columbia.
Can extended radon stacks in the sub-slab area collect radon gas more effectively than radon stacks with a single suction pit?
An experimental study is currently in progress in NRC’s Test Hut #2 with varying sub-slab stack configurations.
Can foam insulation board, spray foam, sealant and other membrane products be used as sub-slab air barrier to prevent radon entry?
The NRC’s radon research team has conducted a series of radon diffusion and air leakage testing using the RDTC and the mid-scale Dynamic Wall Test Facility.
In addition, the NRC’s radon research team has also joined The Take Action on Radon team in planning the Radon Action Month national campaign, in order to improve the public awareness of radon issues. The team has also published Combating Radon with Scientific Research in Construction Canada Magazine.
Christopher Pezoulas, Business Advisor