Decoupling awake and asleep thermal comfort: Impact on building design optimization

Researchers suggest that humans have different preferred thermal conditions for asleep and awake periods. Yet, current standards underpinning thermal comfort assessment and energy analysis in buildings are exclusively based on awake comfort preferences and do not differentiate between awake and asleep conditions. This study hypothesizes that considering sleep thermal comfort in building performance modeling would significantly impact the energy and comfort performance of building design options and, thus, impact design decisions optimized for these goals. No prior studies have been found to test this hypothesis. A review of research on sleep thermal comfort is conducted to find suggested optimal temperatures for sleeping. Then, the impacts of applying sleep thermal comfort ranges on optimal residential building design decisions were analyzed through a simulation-based analysis. A multi-objective optimization model was developed, first, with standard comfort ranges at all times, and second, with sleep and standard comfort ranges at appropriate hours. Both optimal and non-optimal solutions were analyzed in terms of energy consumption and thermal comfort. The results demonstrated that the design of optimal buildings differs significantly when including sleep thermal comfort (e.g., more windowshading proved to be a more energy-efficient and comfortable solution than when sleep thermal comfort was ignored.) Therefore, the consideration of sleep thermal comfort impacts building design decisions and provides energy-saving opportunities. This research implies, for the first time, that the simulation-aided design process of high-performance buildings where sleep occurs should consider sleep thermal comfort separately from awake comfort to better inform the decision-making process.