A feasibility study was conducted using a preliminary knowledge-base which contains information about how the illuminance levels in a test model were affected by five different variables: window size, shape, vertical location on the façade, horizontal location on the façade, and existence of a horizontal shading device. This knowledge-base was used to improve three case study buildings with increasingly complex goals. It was found that in each case study, daylighting performance was improved (approached the goal conditions) after design changes suggested by the expert system were implemented.