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A total of 8 mechanically ventilated residential buildings and 8 naturally ventilated residential buildings were selected to analyze the pollution characteristics of indoor VOCs under different ventilation modes in the severe cold area of northeast China. On typical meteorological days in each season, VOCs were detected on site, and ventilation modes were investigated by long-term online monitoring. The test results showed that the TVOC (total volatile organic compounds) concentrations varied greatly in different seasons or different functional rooms, and the TVOC concentration was the highest in winter, with a value of 0.994 mg/m3. The kitchen was the place with the most serious VOC pollution, and the TVOC concentration could reach 1.403 mg/m3. Benzene series and methylsiloxane had the highest detection rates, but the detected concentrations were low, and the average concentrations were 0.025 mg/m3 and 0.013 mg/m3 respectively. Among the VOC types with a detection rate greater than 50%, the average proportions of aldehydes, alkanes, and benzene series were 18.7%, 15.39%, and 14.38%, respectively. And their mass ratios were also high, which were 14.90%, 30.85%, and 15.70%, respectively. The annual daily average ventilation duration of mechanically ventilated residential buildings was 7.84 h longer than that of naturally ventilated residential buildings. The median TVOC concentrations of mechanically ventilated residential buildings and naturally ventilated residential buildings were 0.621 mg/m3 and 0.707 mg/m3, respectively. The fresh air system was applicable in the severe cold area of northeast China. [ABSTRACT FROM AUTHOR]

• DS-STPV windows with different ventilation modes were studied by simulations. • Simulation results were experimentally validated. • An optimal operational control strategy for DS-STPV windows was proposed. • Benefits with the application of DS-STPV windows were demonstrated. • DS-STPV window could improve the energy performance of buildings. The use of double-skin semitransparent photovoltaic (DS-STPV) windows is well recognized as an efficient and effective approach for enhancing the building energy performance. However, despite many studies in relation to the technology have been reported so far, there are few investigations focusing on its use in cold regions. In this study, experimental measurement data for a DS-STPV window in terms of power generation and surface temperature were compared with those obtained from EnergyPlus simulations. The measured and simulated results agreed well, which confirmed the reliability of the simulation methodology adopted. On this basis, the energy performance of DS-STPV windows with non-ventilated, inner loop, and air supply ventilation modes was analyzed by simulations performed for winter conditions in cold regions. The results showed that as compared with the other two ventilation modes, the use of air supply DS-STPV windows is capable of reducing the building net electricity use by 18.5% and 20.2%, respectively. Further, an optimal control strategy for DS-STPV windows employed in cold regions was also proposed. It was found that with the use of the proposed strategy, the building net electricity use can be effectively reduced by 3.5% and 12.3%, respectively. Relevant findings of the present study provide an insight into optimal design and control of the DS-STPV windows employed in cold regions. Further, the results presented and the simulation methodology established will also be useful for further development of the technology for energy savings and emission reductions. [ABSTRACT FROM AUTHOR]

Abstract People typically spend many hours a day inside their homes. Outdoor PM2.5, indoor décor, and the activities of residents worsen indoor air quality. Natural ventilation, natural ventilation with a portable air cleaner (PAC), and mechanical ventilation are some of the main ventilation modes. However, limited data are available on the actual performance of different ventilation modes. We conducted a one-year on-site program of measurement in six apartments in Tianjin, China. The results showed that indoor air quality was affected by both outdoor particle concentration and indoor activities (walking, cooking, etc.). Natural ventilation alone cannot guarantee indoor air quality. A mechanical ventilation system could reduce the duration of high indoor particulate pollution periods to some extent; however, whole year monitoring revealed that it was not effective in increasing healthy time ratios. Reduction in CO 2 concentrations above the standard levels through mechanical ventilation is 22.3% more than that through natural ventilation dwellings. Natural ventilation with a portable air cleaner can remove mass particulate pollution rapidly and maintain good indoor air quality with long-time operation. This study is expected to contribute towards the improvement of indoor air quality and the health of residents. Highlights • One-year on-site measurement in six apartments in Tianjin. • Natural ventilation alone cannot guarantee indoor air quality. • Mechanical ventilation system does little to increase healthy time ratios. • Natural ventilation with portable air cleaner can create good indoor air quality. [ABSTRACT FROM AUTHOR]