Thanks to new insights on the impacts that dwellings have throughout their life cycles, there has been increased attention to retrofitting innovative energy systems (IES) in existing housing. This paper uses an explorative case study design to gain more knowledge about the governance aspects of this under-researched topic. The central research question is: Which factors influence the adoption of innovative energy systems in social housing sites during renovation projects? To answer this question, eight large-scale renovation projects in The Netherlands were investigated. These case studies allowed the identification of barriers, enabling factors and perspectives from three main actors-housing associations, tenants and local authorities. It turns out that adopting IES encounters many barriers: lack of trust between project partners, delay in project progress, financial feasibility considerations, lack of support from tenants, lengthy legal permit procedures, over-ambitious project goals, poor experiences in previous projects, and IES ambitions that are not taken serious by key decision-makers. Furthermore. IES were only successfully fitted in three of the eight projects. Moreover, ambitions were lowered as the projects progressed in all the cases investigated. The study calls for further systematic, in-depth comparison of fitting IES in large-scale renovation projects in social housing. (c) 2012 Elsevier Ltd. All rights reserved.