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This study aims to evaluate airborne transmission risk in university towns during the COVID-19 pandemic based on surveys of indoor environmental quality (IEQ). Both on-site measurements and questionnaire surveys were carried out in public buildings in university towns in Changsha, China. Air temperature, relative humidity, and CO2 concentration in one library, ten classrooms, eight canteens, seven restaurants, and sixteen malls were measured. 2220 valid questionnaires concerning occupants’ sensation on thermal environment, air movement, and indoor air quality were collected. A 3-level evaluation method of airborne transmission risk that is dependent on building type and indoor CO2 concentration was developed. Excessive CO2 concentration is found in library (1045 ppm), classrooms (1151 ppm), restaurants (1242 ppm), and malls (1057 ppm). The percentage time of “high risk” accounts for 18–100% in these buildings. The results reveal a serious problem: numerous public buildings in China and probably other resource limited countries are not basically prepared and equipped to cope with airborne transmission. This fact should be taken into account when developing guidelines and formulating mitigation measures. Real-time monitoring and displaying IEQ and thus the transmission risk level should be an important way to be widely implemented in public buildings.

Smart and personalized ventilation systems have been demonstrated with high performance in creating a healthy and energy-efficient indoor environment, but they have been rarely comprehensively summarized and explored in previous studies. With the progressive development of various terminal devices and control technologies, personalized ventilation based on intelligent control is potentially a promising way to achieve efficient control and energy savings in human micro-environments. This study comprehensively summarizes and analyzes the recent studies and common utilization forms of smart ventilation and PV systems that are based on CO2 concentration control, to pave path and provide some guidelines for their integration application for reducing energy consumption and improving indoor thermal comfort. Research shows that the combination of personalized ventilation and smart ventilation is an essential development for ventilation systems. Smart ventilation with demand control logic based on CO2 concentration has been mature enough to effectively improve the effectiveness and comfortable performance of personalized ventilation. However, switching from traditional air conditioning systems to personalized ventilation still requires improved sensors and intelligent control algorithms. In addition, this paper also summarizes the exploratory studies and potential application analysis of machine-learning theories to improve intelligent control of personalized ventilation. To this end, this paper identifies future tendencies for advanced theories, integrated systems, and devices in personalized ventilation systems.

In order to reduce the energy consumption of HVAC systems in buildings, the use of energy-saving solutions is necessary. One of these solutions is ventilation, which is usually used for maintaining acceptable indoor air quality and thermal comfort. As the change in outdoor environment is unpredictable and the occupant control is spontaneous, it is critical to control the windows and HVAC systems to achieve a maximum use of outdoor air for indoor ventilation. A new rule-based control strategy that could change the opening factor of windows is proposed in this study and its effectiveness was tested in five representative climates, ranging from a subtropical region to a severely cold region. A building model was set up and the indoor air temperature and energy consumption were predicted using EnergyPlus. The results show that the proposed control strategy can utilize ventilation to maintain a comfortable indoor environment with an annual uncomfortable percentage in an occupied period lower than 5%, thus leading to an energy-saving rate of 13.5–55.6%. The simulation results indicate that there are periods of ventilation available during the summer in climate zones with hot summers and warm winters, whereas the control strategy has a better energy-saving performance in temperate areas. This study conducted a preliminary exploration for practical applications of the combined operation of controllable natural ventilation and HVAC systems in buildings.