This project will focus on the development of computer algorithms for daylighting effectiveness and energy performance impacts for lightshelves and atriums based primarily on building characteristics and configuration aspects. Both direct sun and diffuse sky conditions will be utilized. A rigorously based experimental model testing program will be conducted in the existing skydome facility to complement full-scale studies with existing buildings. The end products will be achieved through correlational studies and building performance simulations utilizing available computer facilities. The research will lead to a more rational building design procedure for energy utilization and daylighting.