Occupant-centric design for functional and thermal zoning at activity-based workspaces

The COVID-19 pandemic has driven organizations to rethink the role and design of workplaces, emphasizing the need for flexible work arrangements that allow employees to choose their work location, whether at home or in the office. This shift necessitates a re-evaluation of workplace design, leading to the rise of Activity-Based Workspaces (ABWs), which offer a variety of environments tailored to different activities and preferences. In ABWs, workspace choices significantly affect both occupant satisfaction and energy consumption. Understanding Human-Building Interactions (HBIs), which involve the complex interactions between zoning layouts, occupant behavior, and building systems, is vital for optimizing both functional and thermal zoning in ABWs. Developing a design framework that incorporates these interactions is essential to enhance occupants' satisfaction with the work environment and building operational performance.This PhD study aims to propose an occupant-centric zoning design framework that considers the interactions between zoning layouts, occupants' space usage, and building operations and show that the framework can offer a range of optimal designs with high operational performance, i.e., thermal comfort and building energy performance, during early design. Additionally, resolutions of occupancy and thermal comfort modeling and HVAC controls are introduced to examine the appropriate complexity of models for the design framework. The definition of "occupancy resolution", which was initially defined for occupancy data, is extended to represent the complexity of occupancy and thermal comfort modeling and the corresponding resolution of HVAC controls.Three case studies were designed to analyze the required occupancy resolutions with different workplace settings and evaluation metrics and demonstrate the significance and benefits of the proposed design framework: (1) evaluating the impact of different occupancy modeling resolutions on building energy prediction performance for a university building with a conventional workplace strategy, (2) investigating the impact of HVAC control and thermal comfort modeling resolutions on occupant-centric control (OCC) performance (i.e., thermal comfort and building energy usage) for a conventional office building, and (3) exploring the impact of occupancy and thermal comfort models and building operations on optimal zoning designs and the resulting operational performance with conventional and flexible workplace strategies.The findings indicate that selecting occupancy resolutions depends heavily on building operations, including workplace strategies, which control the availability of spaces and occupants' space usage, as well as HVAC controls. A basic approach is to match the thermal comfort modeling resolution with the HVAC control resolution for balancing the operational performance and data acquisition costs when adopting OCC. Otherwise, a mismatch between HVAC controls and thermal comfort models can result in 6–12% and 10% potential losses of occupants' thermal comfort and energy savings, respectively. However, in ABWs with the elastic comfort-driven workplace strategy, a higher resolution is needed to capture individual preferences even with zone-level HVAC controls. For occupancy modeling, schedule-based models can outperform agent-based models (ABM) in energy simulation and zoning layout optimization under conventional strategies. However, with the workplace strategy that enhances HBIs, using ABMs significantly improves optimal zoning layouts and operational performance. This underscores the importance of appropriately defining design problems with objectives, influential factors, and their interactions when using ABMs.The developed occupant-centric zoning design framework proved the significance of considering the interaction between zoning layouts, occupants' space usage, and building operations when designing ABWs through an actual retrofit building project. The ideal functional and thermal zoning varied significantly across different occupanc modeling and building operation scenarios. The results showed ABWs' potential to enhance building operational performance with ABM, OCC, and the elastic comfort-driven workplace strategy, increasing occupants' thermal comfort by 6–8% and reducing energy usage by 9–13%. These findings underscore the importance of considering HBIs in designing ABWs to improve thermal comfort and energy efficiency from an occupant-centric perspective.