As an added benefit, the PFT method will also exactly determine the overall air exchange rate of a building under real-life conditions. Using this method, one can determine the positive effect of ventilation solutions including window opening. The NRC enhanced this method by allowing concentrations of potentially harmful volatile organic compounds (VOCs) to be quantified at the same time. This feature allows one to characterize the air quality in every zone of a building, and understand the relationship between airflows and IAQ. Obviously, this feature reduces the analytical cost, when both ventilation and VOC determinations are required for IAQ investigations.
The PFT method is a new capacity for Canada, and was essential to perform the study presented here. It is now also available for all Canadian IAQ investigators when looking for the best ventilation options for their clients, as well as for solving issues.
Conclusion
Achieving the desired IAQ is a complex enterprise, especially in climates where natural ventilation is not an option in all seasons. Several elements need to come together to achieve this objective, including controlling emissions from building materials and consumer products, improving the quality of supply air (in case the ambient air is polluted), reducing ingress of soil gases like radon, and limiting the infiltration of breathable particles and gases through the building envelope.
Controlling the pressure differences between the zones in the building and the outside atmosphere contributes to the objectives of ventilation, such as improving IAQ, managing better the moisture in building envelopes and materials, and reducing the risk of mould growth.
Limiting undesired airflow from zone to zone, and finding optimal pressure differences supporting the objective of ventilation, which is the outcome of balanced ventilation, will support the generation of the desired healthy IAQ, while respecting project’s energy and sustainability goals.
The results presented here originate from the 2017 heating season and were presented at the 39th Air Infiltration and Ventilation Centre (AIVC) Conference (2018) (for more information, read “Residential balanced ventilation and its impact on indoor pressure and air quality” by Boualem Ouazia, Daniel Aubin, Doyun Won, Wenping Yang, Stephanie So, Chantal Arsenault, Yunyi Li, and Jacqueline Yakobi-Hancock, presented at the 39th Air Infiltration and Ventilation Centre (AIVC) Conference, 2018). A full report on this study was released in April 2019 (Consult “Residential balanced ventilation system effectiveness and tested indoor pressure and air quality impacts” by Boualem Ouazia, Doyun Won, Daniel Aubin, Wenping Yang, Stephanie So, and Chantal Arsenault, National Research Council Canada (NRC) report No. A1-009760, March 2019). NRC continues to work with partners from industry and the health community to improve ventilation with the objective of providing healthy indoor environments for all Canadians using energy-efficient approaches.
| THE TRACER GAS METHOD |
 Photo courtesy NRC Tracer gases are used to show building professionals how potential gaseous contaminants may move through buildings, and from unoccupied to occupied zones, as they behave like, or very similar to, the volatile contaminants one is interested in measuring. The experimental technique is based on the evaporation of volatile gases called perfluorocarbon tracer gases (PFT), and was originally developed at the U.S. Brookhaven National Laboratory (read the “Air filtration measurements in a home using a convenient perfluorocarbon tracer technique” article by Russell N. Dietz and Edgar A. Cote). In every zone of interest, a source of a specific tracer gas called an emitter is deployed, passively releasing a specific tracer gas at a constant and known rate. Simultaneously, tracer gases floating around from all zones of interest are passively sampled in all zones of interest. By determining in the laboratory the quantities of tracer gases sampled, one can determine how air flows within a building. |
Hans Schleibinger, PhD, is an environmental engineer who has worked in the areas of air and water pollution control, prevention of mould growth, hospital hygiene, toxicology, and environmental analysis in Germany. He has been a senior research officer at the National Research Council Canada (NRC) since 2005, evaluating products and technological solutions and creating evidence-based knowledge for Canadian stakeholders. He can be reached at hans.schleibinger@nrc-cnrc.gc.ca.
Doyun Won, PhD, is a senior research officer at NRC, working on indoor air quality (IAQ) and ventilation. She has 20 years of experience in testing building materials and consumer products for chemical emissions, predicting their impacts on IAQ, and developing IAQ mitigation strategies. She earned her PhD in Environmental Engineering from the University of Texas at Austin. Won is a member of the International Standards Organization (ISO) Technical Committee 146-SC6 on “Indoor Air”. She can be reached at doyun.won@nrc-cnrc.gc.ca.
Boualem Ouazia, PhD, is a senior research officer at NRC as an expert in the areas of HVAC, ventilation and air distribution effectiveness, heat/energy recovery ventilation, thermal comfort, IAQ, and environment. A mechanical engineer, Ouazia is the community infrastructure thrust lead for NRC’s Arctic Program, leading research projects focused on improving housing for northern and remote communities and IAQ for Canadians. He can be reached at boualem.ouazia@nrc-cnrc.gc.ca.
Daniel Aubin, PhD, is an environmental chemist who has worked in both the areas of outdoor and indoor air chemistry in Canada. Aubin is a senior research officer at NRC and the team leader for the Indoor Air Quality Group. His recent work has focused on developing and validating methods and technologies to reduce occupant exposures to harmful pollutants. He has expertise in the areas of environmental analytical chemistry, children’s environmental health, building science, and in the conduct of intervention field studies with human participants. He can be reached via e-mail at daniel.aubin@nrc-cnrc.gc.ca.
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