For the last decades, designers have been facing a new challenge: design products and services with lower environmental impact and greater value to customers and society. To meet these expectations, the environmental assessment of solutions in design teams must be relevant and commonly accepted. This is es-pecially true in the early phases of the Product Development Process when details of the concepts are not yet defined. Literature tends to prove that evaluations of ideas vary substantially, meaning that designers do not have the same understanding of ideas or criteria. To organize a more efficient assessment stage and to obtain a reliable assessment, it is necessary to implement new procedures. The subsequent research question is: what are the relevant factors to assess early design concepts from the environmental perspective and create an ad-hesion to promising ideas (called 'best nuggets') in a design team? To do so an experiment was conducted with four groups of eco-design experts. They were asked to evaluate the environmental relevance of the de-sign concepts generated during two previous eco-design sessions. Some criteria were common to all groups of designers, such as the potential reduction of environmental impact on each life cycle stage, and the potential reduction of each type of environmental impact (i.e. resource consumption, toxicity, etc ...). Besides, specific evaluation criteria and their effect on the group adhesion were analyzed: the risk of an environmental impact transfer and the potential positive influence on user. Some results and recommendations are presented in this paper.