Thermal and lighting performance of toplighting systems in the hot and humid climate of Thailand

This study evaluated the potential of toplighting systems in the hot and humid tropics by using Bangkok, Thailand (latitude 13.7????N) as a test location. The analysis tested both the thermal and lighting performance of three toplighting systems. Toplighting, designed for use in one-story buildings or on the top floor of taller buildings, yields a uniformly distributed light throughout a space. However, in lower latitude locations, where there is no heating period, heat gain is a critical design issue since it significantly affects the annual energy consumption of the building. Accordingly, the decision to use toplighting in these locations needs to be carefully examined before any design considerations occur. In this study, the thermal and lighting performance of three toplighting systems were compared. For the thermal performance, total cooling loads, heat gains and losses, and interior temperature were evaluated. The lighting performance parameters examined were daylight factor, illuminance level, light distribution, and uniformity. EnergyPlus was used as the thermal analysis tool, and RADIANCE, along with a physical scale model, was used as the lighting performance analysis tool. The sky conditions tested were overcast, clear sky, and intermediate sky. Results have shown that, for locations with hot and humid climates with variable sky conditions such as Bangkok, Thailand, the roof monitors perform better than the other two systems in terms of the thermal and lighting performance. With similar cooling loads, the roof monitor provides better illuminance uniformity than the skylights and lightscoops, with adequate illuminance level (at mostly higher than 500 lux).