As cities densify, more people are living in multi-unit residential buildings (MURBs). In MURBs, suite air contains some combination of outdoor air that has infiltrated through the building envelope, air from mechanical ventilation systems, and air from other zones within the building, either other suites or common areas. In MURBs, indoor air quality (IAQ) can vary significantly between zones, depending on the relative contribution of each of these air sources and the contaminant emission profiles within the building.

Controlling inter-zonal air flow improves IAQ (by limiting odour/contaminant transport and improving the efficiency of mechanical ventilation systems) and energy efficiency. This is achieved through compartmentalization:​ the installation of continuous air barriers between individual zones, which isolate zones from one another. Current building codes/standards and certification programs include prescriptive and performance-based requirements that regulate compartmentalization in MURBs. Through a combination of field measurement and simulation studies, this dissertation characterized inter-zonal airtightness and air/contaminant transport in MURBs to, (1) provide updated data on the feasibility of performance-based compartmentalization requirements (assuming typical design/construction practices consistent with base-code prescriptive compartmentalization requirements), and (2) systematically assess the impact of compartmentalization and mechanical ventilation system design/operation on IAQ and energy consumption, to support the efficacy of performance-based requirements and identify how building design/operation practices can improve IAQ.

Field measurement studies found that performance-based targets are easily achievable in concrete MURBs, assuming typical design/construction practices. Partition-level air tightness testing revealed significant inter-partition variability, with suite-to-corridor walls being consistently less airtight than suite-to-suite walls, even after controlling for construction type. These results provide support for performance-based targets and provide designers/contractors guidance on where to focus airtightness efforts.

Simulation studies found that interior/exterior partition airtightness was important for reducing direct suite-to-suite air/contaminant transport. Stairwell/elevator door airtightness was critical for reducing indirect suite-to-suite air/contaminant transport via stairwell/elevator shafts, and improving pressurized corridor ventilation system efficiency. Stairwell/elevator door airtightness was more effective at decreasing the inter-suite variability of fractional contaminant concentrations (the proportion of suite contaminants that originated in other zones), compared to suite partition airtightness. The simulation results highlight the importance of compartmentalization in common areas, as well as suites.