## 1 Introduction  
The agenda of \"urban transition\" in the 21 st century, as applied here, refers to strategies envisioned to attain goals set for: (i) climate change mitigation; (ii) energy efficiency and more broadly; (iii) human wellbeing in the built environment or \"green cities\". The urban transition agenda can thus be viewed as a product derived from the ambitions of international policy documents, e.g., the EU Energy Efficiency Directive [1]. Within this wider context this paper sets out to explore urban transition in Sweden and Denmark with a focus on the built environment, particularly on multi-family housing and their refurbishing. Examples are drawn from both countries, while the policy strategies of the largest cities in the Oresund area, Copenhagen and Malmo, are given special attention. The paper discusses the means used for implementation, the associated investments and the results of major or typical refurbishing projects exemplified by deep renovation of large apartment blocks. National strategies of urban transition are instituted at different governmental levels through national legislation, building regulations and other policy instruments (such as e.g., tariffs and subsidies), to municipal strategies where explicit targets are set for the level of ambition to strive for, albeit without the targets being binding commitments. Many municipalities have passed such transitional agendas, e.g., in the Oresund region, Copenhagen [2, 3], Malmo [4, 5] and Ballerup municipality [6]. These policy documents show common ambitions in the region for this agenda. For the built environment, substitution or expansion with new constructions represent a minor share of the total urban development, consequently urban transition policies in addition to addressing standards for new developments focus on the challenges of refurbishing existing buildings and on upgrading urban space to fit the \"green city\" ambition. On a city scale, these ambitions imply investments in the existing building stock, infrastructure and supportive city functions in order to reach the self-set targets for lower CO\({}_{2}\) emissions (climate change mitigation), higher energy standards (energy efficiency) and \"green cities\". The economic sustainability of energy saving measures within the urban transition agenda cannot easily be isolated from other objectives, due to significant interdependencies. At present it is unclear how these investments are to be distributed among the different stakeholders to meet such broad ambitions. Although investment decisions can be supported by technical calculations of possible energy savings from an economic perspective, other factors influence the long term sustainability from a broader political perspective. Identifying the most cost-effective interventions with respect to specific policy goals depends on the framework conditions for urban transition at the case level, the existing building stock as well as the technical efficiency of available energy solutions, infrastructure and construction technology. Despite their broad scope, many transformation projects have taken a point of departure in energy policies and on financing a transformation of the built environment through savings made from lowering the energy consumption [7]. Thus, the focus on reducing energy consumption and on increased energy efficiency is not only justified by the role of energy in policies, but also by association on the potential economic savings that may provide a lever for other types of measures and implementing projects of urban transition. The role of the government _versus_ the market is a central policy issue, as upgrading of the building stock is largely to be financed by the market. Hence, achieving the set targets and ambitions will require favorable framework conditions conducive of urban transition through e.g., policy instruments aimed atstimulating the desired market behavior (incentives, removal of barriers, reduced uncertainty, _etc._).