An Indoor Environment Demand Evaluation Model for Part Time Part Space Operating Mode in an Office Building

Compared to the 24h full-space indoor environment operating mode, the "part time, part space" operation mode has been proven to reduce the energy consumption from heating, ventilation, and air conditioning (HVAC) systems by more than 10–20% by reducing unnecessary environmental requirements during unoccupied times and spaces. Thus, it is generally regarded as a promising technology for energy saving and emission reduction in the building sector in China. Real time and accurate evaluation of the indoor environment quality (IEQ) and occupants’ demands of time and space is key to the successful implementation of "part time, part space" operation mode. However, the existing IEQ model usually ignores the occupants’ demand in different times and spaces, which leads to unreasonable environmental requirements. Therefore, this study first established an indoor environment demand indicator system and the demand category of a comfortable and healthy environment by adopting the standard induction, literature review and key performance indicators method, and established a "part time, part space" indoor environment demand evaluation (IEDE-PP) model through comprehensive evaluation. Finally, the feasibility and energy saving potential of the IEDE-PP model were verified by case analysis and an energy consumption simulation. The results of the case analysis showed that the IEDE-PP model could determine whether the current environment was in a reasonable state through demand sensing, demand evaluation, and comprehensive demand evaluation. Furthermore, the energy consumption simulation results reported between 6% and 22.3% energy savings when compared with the full time, full space fixed set point operating mode and the actual operating mode without demand feedback. Consequently, the main contribution of this paper was to provide an indoor environment demand evaluation model to guide the "part time, part space" operating mode and achieve building energy conservation and emission reduction.