This paper explores through professional case studies how design solutions produced by expert teams compares to those developed through systematic parametric analysis. While the expert intuition of either single designer or teams helps to rapidly identify relevant aspects of the design problem and produce viable solutions, it has limitation to address multi-criteria design problems with conflicting objectives and searching for design alternatives. On the other hand, parametric analysis techniques in combination with data analysis methods helps to construct and analyze large design spaces of potential design solutions. For the purpose of this study, the specifications of geometric features and material properties of the building envelopes proposed by the expert design teams define the base line to measure the extent of the performance improvements of two typically conflicting objectives: Daylight quality and energy consumption. The results show consistently significant performance improvement after systematic optimization.