Sustainable design is a major trend in diverse disciplines related to the built environment. However, practitioners often find difficult to fully incorporate sustainability criteria during the design process and in its final outcome. Moreover, the adoption of industry-conceived sustainability guidelines tends to be perceived as a restriction or 'checklist exercise', which does not positively impact design activity. The aim of this study is to analyze the practitioner experience during sustainable design process, particularly in relation to the impact of sustainability guidelines (known as sustainability rating systems, SRS) in design decisions from real case projects. This study has been conducted by collecting data for real projects located in Melbourne, Australia, during 2010-2013, employing a hybrid methodology that brings together embedded research, retrospective protocols and linkography to assess the impact of SRS in such processes. It proposes a theoretical approach to assess sustainable design process by quantifying the impact of SRS during design decisions.