Abstract A deep plan layout and internal partitioning and resistances along the wind path in interior spaces make single-sided ventilation the only strategy possible for residential units. In this work, the potential of single-sided ventilation through the introduction of a balcony was investigated. The design of the wing wall at the balcony was investigated to determine its effect on the performance of single-sided indoor ventilation. The methodology used in was computer simulation (computational fluid dynamics or CFD) validated by data on an existing wind tunnel study and the measurements from a selected case study. CFD simulation was conducted on a simplified model of a medium-rise and low-cost residential building in Johor Bahru, Malaysia. Upon validation, the four wing wall depths and three wing wall angles were applied to the balcony, and each was evaluated numerically. Results showed that the provision of wing wall in the balcony could increase the indoor air velocity and airflow rate and improve the airflow distribution in the room if appropriately designed. The indoor ventilation performance was improved by increasing the wing wall size up to a certain depth and deviation of 22.5°. The provision of a balcony with wing walls can be a facade design alternative to improve indoor ventilation and possibly reduce energy consumption in buildings.