Complexity in Design is defined by N. Suh as the measure of uncertainty in achieving the functional
requirements (FRs) of a system within their specified design range. According to his complexity theory, here
is described how integrated design is a way to get a non complex solution for an imaginary time independent
complex problem. Two case studies in the field of furniture design and building design demonstrate how the
integration of the actors concerned by the life cycle of the product can achieve this goal, using a cooperative
design modeller and working with the just need concept.