Integrated building energy-computational fluid dynamics simulation for estimating the energy-saving effect of energy recovery ventilator with CO₂ demand-controlled ventilation system in office space

As ventilation is one of the critical heat loads in an office space, the ventilation rate might be optimized to develop sustainable, low-energy buildings and a healthy indoor environment. To create comprehensive and optimized indoor environmental designs, a building energy simulation (BES)-computational fluid dynamics (CFD)-integrated simulation is used to provide accurate and informative prediction of the thermal and air-quality performance in buildings, especially in the design stage. With the aim of developing an optimization procedure for the ventilation rate, this paper presents simulations that integrates BES and CFD with CO₂ demand-controlled ventilation (DCV) system, and applies them to a typical office space in Japan to optimize the ventilation rate through an energy recovery ventilator (ERV). The transient system control strategy is applied to two different airflow conditions in an office: a traditional ceiling supply system and an under-floor air distribution system. Compared with the fixed outdoor air intake rate, which is referred to as constant air volume ventilation, optimized ventilation systems associated with a CO₂ DCV produces energy savings of 11.6% and 24.1%, respectively. The difference in the energy saving effects of the two ventilation systems is caused by the difference in the ventilation efficiency in the occupied zone. The ventilation rate and ventilation efficiency have a significant impact on the energy penalty of an ERV. Therefore, optimizing the ventilation rate according to a CO₂ DCV system with an appropriate airflow pattern could contribute to both creating and maintaining a healthy, comfortable environment, in addition to saving energy.