Evaluation of lighting conditions in portable classrooms and analysis for alternative daylighting systems

Lighting conditions in multiple classrooms in central Texas were assessed, and the feasibility of improving portable classroom daylighting via alternative daylighting systems was also evaluated. Results indicate that surveyed portable classrooms generally provide sufficient levels of light with artificial lighting systems, but have less uniform lighting distribution than permanent classrooms. To evaluate the daylight availability in portable classrooms, a model was developed and verified using field data. Climate-based daylighting simulation was performed using DIVA for Rhino, which uses Radiance and DAYSIM as simulation engines. Results from the annual daylighting analysis suggest that limited amounts of daylight were available in portable classrooms over the course of a year. In order to assess the feasibility of improving portable classroom daylighting conditions, parametric studies were completed to investigate how different factors affect the levels of light in classrooms. Simulation results suggest that increasing window area and higher window placement allow more light into the classroom. Different external shading systems also affect the indoor daylight level. However, the impact of other factors, including building orientation, ceiling-to-floor height, and classroom length-to-width ratio is minimal. While changing the window systems for an existing portable building can require a large construction effort and financial commitment, retrofitting with tubular skylights is a more approachable option. Daylighting analysis shows eight 356-mm (14-inch) diameter tubular skylights can provide the portable classroom with a sufficient light level for more than 60% of occupied hours. When daylighting alone cannot provide sufficient light, lighting control will successfully combine a daylighting system and an artificial lighting system to provide an adequate lighting environment.