This article stresses the effects of the institutionalization process of Environmental High Quality’s standard (HQE) on the system of professions related to project management of buildings in France. In the wake of the HQE’s approach, a new professional specialty within the construction sector emerged, leading to new tights of cooperation between architects and HQE advisors. The architects’ loss of autonomy and control over the conception of buildings has been initiated by the development of HQE’s standard. This reorganization of the system of profession is the result of an internal segmentation process that is specific to project management professionals (i.e. architects and engineers). In a broader perspective, this professional reorganization highlights the weakening of the traditional authority of established professions and by contrast, the growing appreciation of experts and their knowledge by users. As the environmental standardization relies on expertise dynamics, it constitutes a powerful tool of the reorganization of the system of professions and of professional legitimacies.