In recent years, the Evaluation Department of the Council of Europe Development Bank has conducted a series of independent evaluations of CEB-financed operations in the social housing sector targeting special vulnerable groups. Building on evaluation evidence and experience, two strategic issues are presented: the high level of complexity of such operations and the various facets of their sustainability. This paper underlines the significant learning and accountability potential of evaluations of social housing operations. At the same time, it underscores the added value of a holistic approach to evaluation, in the face of a simplistic, but currently predominant, output-oriented focus during monitoring.