Conference Agenda

Accurate ventilation system sizing is critical to achieving energy efficiency while maintaining acceptable indoor air quality (IAQ) in commercial buildings. Traditional design approaches often assume full occupancy, leading to oversized systems with higher energy consumption. This study investigates the potential of using occupancy diversity factors to optimize ventilation system sizing, balancing energy efficiency with IAQ requirements. EnergyPlus simulations are conducted to model two scenarios for an office building: one assuming all the zones are fully occupied simultaneously and the other incorporating a diversity factor to represent typical occupancy patterns. The simulations produced different ventilation load patterns, allowing a comparison of energy use between the two scenarios. IAQ was assessed by monitoring carbon dioxide (CO2) levels under both scenarios to ensure that applying the diversity factor does not compromise IAQ. The findings indicate that average daily CO2 concentrations during occupied hours remain within acceptable limits even with reduced ventilation loads based on partial occupancy where occupants move between zones and not all zones are fully occupied at the same time. This approach demonstrated a potential 12.5% reduction in total air handling unit (AHU) energy consumption.

Decarbonizing both new and existing buildings rapidly is a multifaceted challenge. Given that people spend approximately 90% of their time indoors, the quality of the indoor environment profoundly impacts health and wellbeing. HVAC professionals are tasked with designing spaces that provide optimal conditions for their intended use while minimizing energy waste. Building ventilation systems are essential for maintaining indoor air quality and occupant health, with the choice of strategy impacting both energy consumption and indoor environmental quality (IEQ).

This paper presents a holistic comparison of three ventilation options, all meeting space conditioning requirements: Variable Air Volume (VAV) systems with terminal reheat, Dedicated Outdoor Air Systems (DOAS) with fan coil units, and DOAS with chilled beams. Using a whole life cycle perspective, these systems will be compared based on energy performance, IEQ impact, utility costs, upfront and lifecycle costs, and embodied and operational carbon emissions. Energy modeling of these options is conducted using IES VE software, with system performance metrics extracted from system and equipment data. The analysis aims to provide insights into the most effective ventilation strategies for achieving both energy efficiency and high IEQ in commercial buildings. By evaluating these systems comprehensively, the paper seeks to guide HVAC professionals in making informed decisions that balance environmental impact, cost, and occupant wellbeing.

This study investigates the dispersion of airborne pathogens emitted by a moving infectious individual in a hospital corridor, focusing on the impact of two distinct ventilation configurations on pathogen behavior. The corridor includes adjacent rooms with two ventilation setups: (1) air return vents near room entrances (Case A) and (2) air supply vents near room entrances (Case B). Pathogens were modeled using CO2 dispersion as an indicator, and simulations analyzed their movement across the corridor and into adjacent rooms.

The results demonstrate significant differences in pathogen dispersion between the two configurations. In Case A, the placement of return vents near room entrances effectively limited pathogen infiltration into rooms, maintaining a higher concentration within the corridor and enhancing pathogen removal via the ventilation system. In contrast, Case B, despite initial expectations of a barrier effect at the room entrances, allowed greater infiltration of pathogens. The downward airflow near the doors formed vortices, carrying pathogens into the rooms, where they spread extensively.

These findings reveal that ventilation design critically influences pathogen dispersion patterns. Case A proved more effective in containing pathogens within the corridor and accelerating their removal from the domain. The study underscores the importance of tailored ventilation strategies in mitigating airborne infection risks in healthcare environments.