The development of a green-building project following a specific reference standard, such as LEED or BREEAM, brings new conditions and restrains for all subjects involved in the process. Within this scope, project management plays a key role for the optimization of the design-project development. This research develops a comparative analysis between the design processes of two case-study projects from the project management perspective, taking into consideration all the activities that negatively affected the project design development. The first project design was developed following the so-called "design-bid-build" process with the fragmentation of the process where each subject and technician involved worked independently from the others. The second project design was developed following a "turn-key" philosophy using a completely integrated process. A new methodology was created in order to analyze the project and evaluate the effects of detected project-management issues under three different points of view: costs, time and building sustainability. Such issues were identified by researchers on the basis of the Lean-definition of "waste". The results showed that process integration affects considerably the cost, schedule and sustainability level of the project design and vice versa, the accuracy of the project management tasks affect the sustainability features of the final building design.