Energy-efficient building retrofits must be approached from three perspectives: law regulation approach, financial incentives approach, and practice approach. The concepts of zero energy building and life cycle energy building are presented as the basis for energy retrofits. Multi-criteria boards to assess the decision-making process are reviewed, analysed, and categorised under an architectonic perspective. Some examples are presented, with different packages of measures, from deep to non-invasive energy retrofits. Passive and active energy generation systems, together with control and management strategies, are the physical elements identified with the potential to improve buildings’ energy efficiency. From a practice approach, this literature review identifies the concept of performance-based architectural design to optimise the planning and design of buildings’ energy retrofits. In addition, tools such as Building Information Modelling are described as part of optimisation processes, as they enable designers to rapidly analyse and simulate a building’s performance at the design stage.

The systemic transformation towards climate neutral cities depends on a dramatic reduction in the use of natural resources, whose use are directly or indirectly associated with greenhouse gas emissions. This means improving Urban Metabolism (UM) and one of the most promising pathways is to promote Circular Economy (CE) practices in the existing building stock, as this approach could reduce global CO2e emissions from building materials by 38% in 2050. However, although resource efficiency is at core of CE, there are still only a few established connections between CE and UM. This paper aims to fill this gap by adopting a three-tier approach based on the dimensions and the spatial implementation of CE (building, neighbourhood and UM scales), with the aim of discussing strategies for CE implementation. Although this not a one-size-fits-all process and cities must adapt these strategies to their local contexts, the strategic actions offered by this paper will facilitate the future development of a dedicated framework for buildings refurbishment using the principles of CE and the definition of multisectoral policy-based actions, in line with the decarbonization goals for cities, which will contribute to improving UM.

The current policies aimed at promoting the decarbonization of existing buildings under the principles of the circular economy are in need of practical measures tailored to local conditions to increase their effectiveness. The lack of standard practices for assessing buildings’ refurbishment strategies toward energy efficiency and CE principles reflects this reality. To tackle this issue, a new framework for refurbishing circular buildings, is proposed in this paper, based on circular procurement and incorporating a lifecycle perspective. This framework articulates a dialogue between local authorities and private stakeholders through a set of steps that encompass building mapping, selective disassembly, (re)design, and (re)build practices, providing opportunities to implement policy-based incentives. The application of the framework within the Portuguese context demonstrates the potential to identify critical moments within the refurbishment process that can materialize in a new set of CE policy actions to be implemented at the building level. These policies are aligned with local construction permitting procedures and take advantage of the resources and incentives offered by the local administration, such as tax incentives.