In system design and product development there is an inherent conflict between refining a concept further or expanding, or even changing concept, as more knowledge about the design is obtained. Here, this is addressed from a mathematical point based on the framework of design information entropy.In this paper it is argued that refinement should only be done to a certain degree within a design space. If the information entropy is to be increased further, it is better to expand the design space. It is shown how this can be done by releasing more design parameters into the design space, and thereby expand it. It is shown that the optimal solution as a function of information entropy makes transitions to expand the design space along a Pareto front. An important assumption is that the influence of design parameters follows a negative power law, i.e., is consistent with the Pareto principle. This assumption is supported with a couple of example.