Transformative portfolios in the Dutch municipal heat transition: a challenge for intermediation

Research on transition intermediation has not yet explored what strategies intermediaries can adopt, or what challenges they face, when pursuing transformative goals in projectified environments in more mature phases of transitions. This study conceptualizes transformative portfolios (coherent and coordinated sets of projects and interventions) as relational infrastructures: principles and mechanisms through which interventions are strategically bundled, coordinated, and dynamically managed. A longitudinal case study of the Dutch Social Innovation Energy Transition program (SIE-2), supporting ten municipalities in developing heat transition portfolios, shows how intermediation initially focused on creating shared narratives and selection logic, before gradually expanding toward aligning projects, fostering learning across interventions, and structuring municipal heat programs. These efforts increased portfolio directionality, coherence, and learning potential. The study furthermore demonstrates that supporting transformative portfolios exceeds the capacity of single intermediaries and requires coordinated ecologies of intermediaries, while revealing municipal constraints related to finance, sectoral silos, learning, and long-term programmatic capacity.