The use of daylight for the illumination of building interiors has the potential to enhance the quality of the environment while providing opportunities to save energy by replacing or supplementing electric lighting. Moreover, it has the potential to reduce heating and cooling loads, which offer additional energy saving opportunities, as well as reductions in HVAC equipment sizing and cost. All of these benefits, however, assume proper use of daylighting strategies and technologies, whose performance depends on the context of their application. On the other hand, improper use can have significant negative effects on both comfort and energy requirements, such as increased glare and cooling loads. To ensure proper use, designers need tools that model the dynamic nature of daylight and accurately predict performance with respect to a multitude of performance criteria, extending beyond comfort and energy to include aesthetics, cost, security, safety, etc.