This study aims to evaluate and compare the indoor air velocities and thermal environment inside different generations of public residential buildings developed by the Housing and Development Board (HDB) of Singapore and analyze the impact of façade design on the indoor thermal environment. To achieve this goal, several case studies were carried out, namely, five typical HDB blocks built in different generations from the 1970s to recent years. Firstly, these five blocks with different façade design features were simulated to obtain the indoor air temperatures for both window-closed and window-open scenarios by using the EnergyPlus V22.2.0 (U.S. Department of Energy) and Design-Builder v6 software(DesignBuilder Software Ltd, Stroud, Gloucs, UK). Meanwhile, the computational fluid dynamics (CFD) simulations were conducted to obtain the area-weighted wind velocities in the corresponding zones to evaluate the indoor thermal comfort. Accordingly, the effects of façade design on indoor air temperatures under both the window-closed and window-open conditions were compared and analyzed. Positive correlations between the facades’ window-to-wall ratio (WWR) and the residential envelope transmittance value (RETV) and T_a were confirmed with statistical significance at a 0.05 level. Furthermore, the indoor thermal comfort based on the wind open scenarios was also investigated. The results indicate that the thermal environment can be greatly improved by implementing proper façade design strategies as well as opening the windows, which could result in an average 3.2 °C reduction in T_a. Finally, some principles were proposed for the façade design of residential buildings in tropical regions with similar climate conditions.