Double-loaded affordable apartments are commonly seen in tropical developing countries to maximize total floor areas. However, the double-loaded apartments would possibly cause poor cross-ventilation, particularly on the leeward side of the buildings. This study aims to propose an alternative design for double-loaded affordable apartments for efficient indoor ventilation performance on the leeward side of the buildings. The alternative apartment design primarily involves the following three key building elements: a closed-vertical void, an open pilotis, and a wind fin. We conducted a detailed wind tunnel experiment, followed by CFD simulations to analyse the effects of the proposed new design on indoor ventilation performance compared to an ordinary apartment building with an open-vertical void. A systematic validation study was conducted for 3D RANS CFD models based on the results of the wind tunnel experiment in terms of grid sensitivity and turbulence models to confirm the accuracy of the CFD models used. It was found that the closed-vertical void of the proposed design distributed wind pressures to the leeward side of the building more than those by the open-vertical void of the ordinary apartment. The proposed closed void design provided better indoor ventilation for both sides of a double-loaded apartment building. This study would help understand more details about passive cooling strategies for affordable social housing, especially in the tropics, where natural ventilation is strongly needed.