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Single-sided ventilation rate is difficult to accurately predict because it has a complex relationship with many factors, including the direction of the approaching wind and building envelope features. In addition, the incursion of outdoor pollutants into the interior through a ventilation opening has been recognized as a serious threat to indoor air quality (IAQ). This article presents on-site measurements of the ventilation performance and IAQ in four high-rise residential rooms in Hong Kong. Key parameters including the air changes per hour, respirable suspended particulate matters (PM: PM 10 and PM 2.5 ), and total volatile organic compounds were continuously recorded over a specified period. A comparison of cases with floor-extended and window-like openings is made. The results indicate that single-sided ventilation performs well regardless of the orientation of the apartment room and the configuration of the opening. Previous empirical models based on single-room buildings are not reliable in determining the ventilation rate of high-rise buildings. The measurements reported here also identify an important route for the incursion of outdoor pollutants, namely the downward re-entry of aerosol particles from an upper unit to a lower unit in the same building. A combination of gravitational and wind effects means this downward transport route significantly increases the PM 10 and PM 2.5 concentrations in the lower room.

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Balconies are green features commonly used in residential buildings to improve natural ventilation and air quality. Small vents, if mounted with an acoustic silencer, can reduce noise penetration while still allowing natural ventilation to occur. In this study, the computational fluid dynamics method is used to investigate numerically the effect of balconies with small upper and lower vents on the ventilation and air quality of the 4th, 5th and 6th floors of a 10-storey building. The results show that balconies can significantly increase the natural ventilation on these floors and generally have a more positive effect on the improvement of natural ventilation and the reduction in pollutant concentration on the floor on which they are located rather than on the levels above or below. Practical application: This study will help designers and engineers understand more about the effect of balconies and lower and upper vents on natural ventilation and indoor air quality in buildings. This study will also help them to incorporate with confidence the design of balconies with lower and upper vents.

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