<![CDATA[Thermal and lighting conditions are important parameters affecting reading comfort, particularly in tropical buildings where external heat loads and building openings may cause non-uniform environmental conditions. This study evaluates the spatial distribution of air temperature, relative humidity, and illuminance in the reading room of the West Kalimantan Library using an Internet of Things (IoT)-based monitoring system. The system was developed using an ESP32 microcontroller integrated with DHT22 and BH175 sensors to measure temperature, relative humidity, and illuminance. Real-time data acquisition and transmission were conducted using the Message Queuing Telemetry Transport (MQTT) protocol. Measurements were performed at 20 observation points to characterize the spatial variability of indoor environmental conditions. The collected data were visualized through spatial distribution maps using the Inverse Distance Weighting (IDW) interpolation method and three-dimensional surface plots. The results showed that the average air temperature was 26.7 °C, which remained within the specified thermal comfort range. However, the average relative humidity of 72% indicated relatively high humidity conditions. Illuminance showed substantial spatial non-uniformity. Areas near windows recorded illuminance levels exceeding 800 lux, which may cause glare, whereas approximately 70% of the reading room area had illuminance levels below 200 lux. These findings indicate that the existing cooling and lighting systems have not provided homogeneous environmental conditions throughout the reading room. The developed IoT-based monitoring and spatial mapping system can serve as an effective evaluation tool for assessing indoor environmental conditions and supporting improvement strategies for cooling and lighting systems.]]>
