The Relationship of Indoor and Outdoor Thermal Variables to Create an Energy-Efficient Modern House in the Tropical Mountains of Indonesia

The rainy season in highland areas often decreases indoor thermal comfort, making residents feel uncomfortable in their own homes. To address this issue, an evaluation of the thermal performance of residential spaces is necessary to identify the rooms offering the higher comfort during this season. This study aims to determine the most thermally comfortable space in highland houses during the rainy period. A quantitative research method was employed, focusing on key thermal parameters—air temperature and relative humidity—as the most influential factors affecting indoor comfort. These variables were measured continuously for 30 consecutive days, 24 h a day, using a digital hygrometer. Data logging was conducted at 10-min intervals in five different spaces: the terrace, living room, family room, bedroom, and kitchen. The analysis reveals that among all observed rooms, the bedroom consistently maintained the highest average air temperature. Interestingly, the average temperature in the bedroom closely approached the local thermal comfort threshold of 24 °C, which is considered ideal by the highland community. This finding implies that the bedroom provides the most comfortable microclimate for residents during the rainy season. The results also highlight the importance of spatial layout, insulation, and ventilation in influencing indoor thermal conditions. This research contributes to the broader discourse on climate-responsive housing design in tropical highland regions, offering valuable insights for architects, urban planners, and policymakers aiming to improve indoor living conditions in similar contexts.