Mitigating Cooling Waste: The Impact of Temperature Heterogeneity in Multi-zone Commercial Buildings

Centralized HVAC systems in multi-zone commercial buildings often create cooling distribution imbalances when satisfying heterogeneous thermal demands. Prioritizing the most demanding zones can lead to overcooling others, resulting in “wasted cooling” when air is delivered to zones already below their heating setpoints. This inefficiency is exacerbated by fixed minimum airflow rates, often set conservatively high, which force conditioned air into zones irrespective of their low thermal loads. This thesis presents a practical, data-driven methodology using standard Building Automation System (BAS) data to (i) allocate AHU-level cooling energy to individual zones, (ii) diagnose cooling distribution imbalance by quantifying “wasted,” “marginal,” and “effective” cooling based on zone thermal states, and (iii) evaluate a theoretically modeled minimum airflow reduction strategy. We simulate the potential for direct waste reduction by lowering minimum airflow rates towards ASHRAE guidelines in zones operating at these minimums with low thermal load. While this first-order simulation likely overestimates savings in actively cooled zones due to unmodeled system dynamics, it serves as a powerful diagnostic, quantifying the scale of potential inefficiency (e.g., 15-30% reduction in wasted cooling in most buildings) and indicating substantial direct waste reduction achievable in overcooled, low-load zones. The proposed diagnostic framework, supported by an interactive web visualization tool, offers scalable metrics for identifying and addressing cooling energy waste, primarily by highlighting deviations from ventilation best practices and the potential of targeted minimum airflow adjustments.