Traditional houses of Indonesia were designed according to the rural environment, which had the maximum shading, natural ventilation, and minimum building heat gain. Currently, high-density buildings and exposed to solar radiation because of minimum vegetation shading are significant factors affecting energy efficiency. Indonesia is in a tropical climate, which is represented by geographical altitude, lowland, and upland. The altitude difference effects on environment variation. The study aimed to evaluate the building's thermal performance under the natural lighting effect of traditional tropical houses using the experimental model and the Ecotect Analysis program based on the field study data. One of Indonesia's traditional houses, Javanese house, was taken as the study object. The study recorded the shading of the Javanese traditional building model in the relationships with solar radiation penetration and natural lighting interruption. The results showed that the difference in solar radiation distribution on the roof surface between lowland and upland does not affect shading distribution. The building transition space has the capability to change the air temperature and reduces the glare from daylight or radiation effect from sunlight. Both in lowland and in upland, lower sky clearness effects on dropped room natural lighting for much time. Moreover, the unshaded and the higher illuminance areas receive a higher temperature.