Long-Term Monitoring of IAQ in a High-Rise Multi-Family Building with Pressurized Corridor Ventilation in Vancouver, BC

Ventilation in multi-family buildings throughout North America is typically provided using a pressurized corridor system whereby make-up air pressurizes the corridor and passes in to the suites. The system relies on the directed airflow from the corridors to the suites to provide proper ventilation to maintain indoor air quality requirements. Previous studies have indicated that a majority of the designed ventilation air is not being delivered to the suites. This leads to potential for indoor air quality issues and occupant complaints of discomfort. Temperature, relative humidity, and carbon dioxide (CO₂) sensors were installed in suites of a 13 story multi-family building in Vancouver, BC to monitor indoor air quality between August 2012 and August 2015. Measurements were recorded at 1-hour intervals to allow for a comparison of indoor conditions during different seasons and between suites within the building. Significant differences were found when comparing the indoor air quality between suites located on the upper floors (9-12) and the lower floors (2-4). The CO₂ concentrations in the upper suites exceeded 1000ppm less than 5% of the time compared to 55-85% for lower suites. The difference in CO₂ concentration can be attributed to higher ventilation rates provided by the mechanical system as measured using both perfluorocarbon tracer testing and continuous differential pressure measurements. CO₂ concentrations showed a cyclic profile with the highest concentrations seen during December and low concentrations in July. The range of average monthly CO₂ concentration was greater for suites on the lower floors (800ppm to 1800ppm) compared to the upper floors (550ppm to 800ppm). The lower summer CO₂ concentrations in all suites are attributed to occupant window opening behavior providing improved ventilation. Temperature and relative humidity measurements throughout the study were typically within the design parameters (21 to 25° C and 30% to 60%, respectively) for all suites. A trend for higher indoor dewpoint temperature was found in suites on lower floors leading to greater potential for condensation and mold growth. The elevated CO₂ concentrations found in this study are greater than those proposed from ASHRAE ventilation guidelines and may have detrimental effects on building occupants. The results at this case study building are likely representative of conditions of many low to high-rise multi-family buildings ventilated with pressurized corridor systems. Alternative ventilation methods are recommended to improve indoor air quality and reduce occupant exposure.