In this paper, we propose an expert system for daylighting in architecture which is used to guide a goal-oriented, user-interactive design process. This system is supported by a knowledge-base which has been populated using a set of previously completed simulations using the Design of Experiments methodology. The knowledge-base contains information regarding the effects of a variety of design conditions on resultant daylighting performance. Eighty different design conditions are considered, encompassing two different values of ten design variables on four facades. Daylighting effects are considered for three times of day, for three seasons, and for five zones. The use of the knowledge-base as both a stand-alone resource and as a component of the expert system is considered. Within the expert system, the knowledge-base provides customized information based on user inputs and guides an iterative process which improves daylighting performance of the user’s original design.