To achieve sustainability with limited global energy resources, minimizing energy consumption and utilizing local materials are essential. In Aceh, Indonesia, traditional houses have evolved over centuries, integrating passive design features that enhance thermal comfort. This study analyzes the thermal performance of Acehnese Traditional Houses using CFD simulations and direct measurements to assess their effectiveness in maintaining temperature stability in a tropical climate. The findings indicate that these houses exhibit good thermal performance. Wind speed distribution inside the building at 08:00 ranges from 0 to 1.6 m/s, with incoming air speeds of 1–1.4 m/s. At 12:00, wind speed increases to 0–2.7 m/s, with incoming air at 1.9–2.5 m/s, while at 16:00, wind speed varies between 0 and 2.5 m/s, with incoming air speeds of 1.5–2 m/s. Temperature measurements show a gradual increase from 23°C at 08:00 to a peak of 29°C between 12:00 and 14:00, followed by a decrease to 27°C by 16:00, demonstrating effective heat regulation. This study confirms that passive design strategies, such as natural ventilation and local materials, significantly contribute to indoor temperature stability. With indoor temperatures remaining within the thermal comfort range 80% of the time, Acehnese Traditional Houses provide valuable insights for sustainable architecture in tropical regions. Future research should explore the impact of extreme weather and potential design adaptations to further enhance thermal efficiency.