Indoor Environment Improvement and Energy-Saving Effects of Light Shelf System with Integrated Radiant Heating and Cooling Panel

Achieving good daylighting while maintaining thermal comfort and reducing perimeter energy use is a key challenge in low-energy office buildings. This study developed a thermally activated light shelf (TALS) system that integrates multiple functions into a conventional light shelf. The top surface blocks excessive perimeter light and reflects daylight deeper into the room, while the bottom surface operates as a radiant heating and cooling panel using circulating warm or cool water. To evaluate the system, full-scale empirical experiments were conducted in a mock-up test bed with two identical office-like cells under the same boundary conditions; one cell was equipped with TALS and the other served as a reference. Indoor thermal environment indices and heating and cooling energy use were monitored during winter and summer. The TALS room achieved ISO 7730 Category A comfort more frequently, with Category A cumulative duration approximately 3.4 times longer in winter and 7.8 times longer in summer compared with the non-TALS room. In addition, heating and cooling energy were reduced by about 39.2% and 7.7%, respectively. These promising results are based on a single prototype and climate, and further studies are needed to optimize TALS capacity and window-related heat loss.