The novel framework addresses the difficulties outlined in the previous section by mapping the phases of building refurbishment and their interconnections to determine points of communication among stakeholders. As such, the establishment of a new framework for building refurbishment is crucial for effectively organizing processes and determining steps to overcome the previously recognized challenges, leading to the practical implementation of CE policy.

The methodology for the creation of this Circular Refurbishment Framework is based on the three pillars of CE [6] (waste reduction, resource reduction, and product utility enhancement) and combines three concepts:

• The 9R framework [35];
• The LCA approach [28];
• The Procurement Phases [36].

The 9R framework [35] prioritizes waste avoidance, and the first steps correspond to the pre-use phase (smarter product creation and use), including refuse, rethink, and reduce strategies, while extending the lifetime of products includes reuse, repair, refurbish, remanufacture, and repurpose strategies. The post-use phase includes recycling and recovering. When applied to building refurbishment, the end-of-life of the building is considered when it no longer serves its inhabitants’ needs and requires refurbishment. The other steps of the 9R framework can be applied to building components.

The LCA approach consists of four stages: product stage, construction process, use stage, and end-of-life., and considers the reuse, recovery, and recycling potential. When considering a CE refurbishment context, mapping of the existing building condition is usually the first stage in refurbishment strategies for existing buildings [30,37,38] and is also considered when making decisions about refurbishment options using LCA methodology [39]. After mapping, setting refurbishment options that align with CE is essential to prevent waste and optimize resources.

The procurement phases, as defined in the RIBA Plan of Work [36], are similar to a cradle-to-gate system boundary [28] and include: strategic definition; preparation and briefing; concept design; spatial coordination; technical design; manufacturing and construction; handover; and use.

It should be noted that practices for refurbishing heritage buildings, which are more restrictive regarding demolition and CDW generation, can serve as inspiration for CE refurbishment. It considers the following basic principles: minimum intervention; preservation of the existing historical value and adoption of a compatible technological innovation; compatibility of new materials used in restoration; reversibility of the interventions; distinction of the additions; enhancement of the existing structures [40]. Existing characteristics, protection motives, and enhancement opportunities are also three of the five aspects of sustainable urban heritage management and conservation identified in [41] research. Adopting a tailored approach is also recommended when the refurbishment of historic buildings aims at lowering energy demand and greenhouse emissions [40].

In addition to the inspiration for the refurbishing heritage buildings analysis, the analysis of the overlap of the three concepts identified before, as illustrated in Table 2, was important to the development of the Circular Refurbishment Framework proposed here, which is discussed in the next subsection.

The new framework offered here comprises six stages, as illustrated in Figure 2, and is intended to facilitate CE adoption in building refurbishment. Following the findings above, mapping is the first EOL stage and is dedicated to characterizing the existing building. Setting the refurbishment strategy and preparing the next stage: selective disassembly/demolition, is the subsequent phase, which is followed by the conceptual and detailed designs for construction, which take place at the third stage: (re)design. Stage 4 comprises the (new) products that will be used in Stage 5: (re)construction. Operation is the last stage of the framework, related to the use of the building. The Circular Refurbishment Framework also outlines the necessary actions to close product and material loops by considering maintenance, repair, reuse, recovery, and recycling.

The Circular Refurbishment Framework was designed to mitigate CE challenges by framing refurbishment activities. Its goal is to ensure stage-specific compliance with previously defined strategies for CE adoption in building refurbishment [5], supported by EU policies. Accordingly, the stage-specific solutions, combined with selected transversal strategies, which are elaborated in the next paragraphs, are adopted within the Circular Refurbishment Framework (Figure 2) to operationalize EU policy towards CE adoption, enabling tangible actions.

Mapping, the first stage, is critical to overcoming building characterization gaps and EOL pre-design practices (O2, T1, T2, in Table 1). This stage consists of characterizing the existing situation, setting refurbishment options, and preparing the selective disassembly/demolition stage. The design team surveys the building’s geometry, quality, function, past uses, thermal performance, degradation state, and construction system and materials. This survey forms a snapshot of the existing building. To facilitate CE practices, surveys must include maintenance disassembly guidelines, reuse potential, recovery potential, and recycling potential. This information is afterwards converted into digital datasets and forms the building passports or material passports [20,42,43,44], providing CE information on building materials, components, and products.

Dimensions	Challenges
Economic	E1	Lack of platforms and storage facilities for reclaimed products
	E2	Lack of platforms for CE professionals and CE jobs
	E3	Estimation challenges; short-term blinkers
	E4	Lack of strategies and infrastructures for new CE materials production
	E5	Lack of CE business models
Social	S1	Lack of trust and lack of CE vision for the building sector
	S2	Lack of platforms for CE professionals and CE jobs
	S3	Lack of collaboration between stakeholders (silo mentality)
	S4	Willingness to go around the law
Organizational	O1	Lack of platforms and storage facilities for reclaimed products
	O2	Lack of standard practices for End-of-Life (EOL) and Construction and Demolition Waste (CDW) management (pre design stage)
	O3	Collaboration and management issues
	O4	Issues with manufacturers’ responsibility and approaches
	O5	Constraints for EOL processes implementation on site
	O6	Lack of methodology and standard practices for CE design
	O7	Lack of training skills
Technical	T1	Building-related barriers
	T2	Lack of materials knowledge and technical challenges for CE
	T3	Challenges to EOL implementation
	T4	Production related barriers (materials and technology)
	T5	Barriers to apply new CE oriented design
Environmental	EN1	Toxic materials removal
	EN2	Lack of awareness of CE impact in climate change
	EN3	Lack of awareness of transportation impact in CE in construction
	EN4	Low of energy efficiency at operation stage
	EN5	Lack of methodology of CE evaluation towards climate change mitigation
Policy	P1	Lack of platforms and infrastructures for reclaimed materials, components and products
	P2	CDW related barriers
	P3	Lack of consistent regulatory framework for CE
	P4	Reclaimed materials related barriers
	P5	Lack of knowledge among stakeholders
	P6	CE business related barriers

Given the complexity of the information involved, the adoption of a building information modeling (BIM)-supported methodology is recommended [45]. For instance, methodologies like Historic BIM (HBIM) [46] comprise data collection and processing from laser scanning/photogrammetry and BIM models with historical parametric components. Furthermore, certification systems like GBC Historic Building Certification from Leadership in Energy and Environmental Design (LEED) have protocols to evaluate sustainable heritage renovation, with on-site study and diagnostic investigations to be inserted in a BIM-model and a building passport (historic building identity card). Knowing existing building construction systems is also an issue in the mapping stage, which can be overcome with archetype-based information [47,48] and a building automated characterization methodology [49]. Mapping is an important stage to provide data on construction age and building materials [50], the state of conservation, and the roof (area and orientation), which are usually not available. Materials passports could be produced by BIM models providing data describing pre-defined characteristics of materials in products, which may facilitate their use for recovery and reuse during deconstruction projects.

Building from existing EU policies, energy performance certificates (EPCs), which constitute the basis for assessing the minimum energy performance standards for existing buildings [2], could be coupled with building passports to tackle the challenges of a lack of standard practices for EOL and CDW management at the pre-design stage, a lack of material knowledge and related technical challenges for CE and building-related barriers (O2, T1, T2, Table 1), and map the building’s intrinsic characteristics. Moreover, building passports could also support refurbishment strategies by serving as baseline information for the building renovation passports and building digital logbooks included in the renovation wave [2]. In parallel, guidelines for building passports, adapted to national contexts, should be developed to enable CE adoption in subsequent stages, namely: implementing EOL on site; forwarding materials for reuse, recovery, or recycling (E1, O1, P1, Table 1); performing CE and Level(s) Framework assessments [18]; and conducting material flow analysis at urban scale. Environmental Product Declarations (EPD) should also be generalized for all construction products and contain circularity data.

After mapping, a briefing with the client may be used to validate the strategic definition of future refurbishment design and circularity potential, and this constitutes the second stage—selective disassembly/demolition. Here, disassembly and selective demolition criteria are defined, constraints are identified, and plans for on-site implementation are developed. These plans include setting up CDW management, polluted material sorting and removal, onsite collection, inventory, and storage, according to previously set CE strategies. Elements to be maintained and repaired should be kept in the building, while elements to be reused should be listed, recovered, and stored. Furthermore, inventory, selective collection, and transportation for reclaimed storage facilities are also necessary for recycling, recovery, and reuse of products if not integrated into the future design. These procedures aim to tackle O5, T3, and EN1 constraints (Table 1). During disassembly works, any unexpected challenges must be reflected in multi-level updated information and strategies: the building passport, the BIM model, and the refurbishment design, involving all stakeholders (S3, Table 1).

However, some conditions related to the policy dimension need to be met first: new guidelines towards CE for EOL implementation on site, CDW management, and asbestos waste treatment could be developed, eventually by adapting waste regulation [51] to CE prerequisites [35], together with permits, controlling, and monitoring mechanisms (O5, T3, EN1, P2, Table 1). These actions should be complemented with training and raising awareness among construction workers about the reduction of CDW and selective collection of products (O7, S2, Table 1). In addition, online platforms and storage facilities for reclaimed products should be created and updated to enable materials’ reuse, recovery, or recycling (E1, O1, P1, Table 1). In the latter case, the global vision for CE in construction goes beyond these infrastructures with the definition of new vision strategies for CE material production (S1, E4, Table 1).

After selective disassembly, the existing building is a “blank page” for the new conceptual design, spatial coordination, and technical design. The (re)design stage emerges, whose key actions are methodological, standardized practices, and assessment for circular refurbishment design, involving all stakeholders. Providing clients with cost estimation and long-term CE benefits regarding costs, GHG emission reductions (E3, Table 1), and assuring a good design using reused, recovered, and recycled materials is essential for their agreement on CE adoption. Design decisions could be supported by multi-objective optimization (clients’ specifications, multiple uses during a building’s lifespan, CE principles, climate change impact, etc.) (T5, Table 1). Defining principles and a methodology for CE refurbishment design includes keeping as much as possible from the existing building, designing for adaptability and flexibility, improving standardization and modularity, designing for disassembly, designing with reclaimed products, ensuring sustainable management of end-of-life waste, and promoting energy efficiency at the use stage (O6, T5, EN4, Table 1). Establishing a BIM-based quantitative assessment for CE is indispensable to assess refurbishment design and project delivery, namely by defining indicators based on the above-mentioned principles, including transportation and lifecycle climate change impacts. Additionally, developing a material hierarchy based on the GHG emissions and circularity indicators might be useful when selecting the best design options (O6, T5, EN2, EN3, Table 1). Technical guidance and specific training should be provided to practitioners for CE refurbishment design (O7, Table 1).

At the policy level, the definition of a regulatory framework for CE refurbishment, together with the definition of a methodology and standardized practices for CE design, estimation, and assessment, will be essential to tackle challenges E3, O6, T5, EN2, EN3, EN4, EN5, and P3 (Table 1). LCA methodology [52] should be used more consistently and adopted for assessing buildings and construction environmental impacts, making use of BIM technologies, although new developments can be made with the wide adoption of the Level(s) Framework and the upcoming strategy within CEAP [16]. Solutions to CE adoption must be transposed, at this stage, to national regulation, as there is country-specific regulation to be considered.

The development of a new concept of endogenous material use occurs in parallel with design and on-site practices for CE refurbishment. Exploring the local or regional capacity on material supply through anthropogenic stock is the first step to reduce transportation and identify gaps that lead to potential business opportunities. This stage calls for the use of eco-design principles by optimizing material use, reducing/eliminating hazardous materials and raw materials, increasing products’ lifespan, designing for disassembly, designing for standardization, using secondary materials and recovered components, and selecting bio-based materials, all of which are in line with CE. Furthermore, these principles should be complemented with standards, requirements, and deliverable specifications for CE products and materials, with implications for the durability and reparability of materials and products. Developing new specific insurance products for CE products should help to avoid over-specification and over-design (E4, O4, T4, P4, Table 1).

At a policy level, the European Commission has a key role in promoting standardization and sustainability in industrial production, including CE principles of reuse, recovery, and recycling of waste, which will help to tackle E4, O4, T4, and P4 challenges (Table 1).

(Re)construction, the fifth stage, should consider the implementation of CE refurbishment design in the building, keeping in mind CE principles and tracking the challenges that might occur, making design adjustments. Training skills for CE among construction workers and control offices is necessary, and the design team should follow building refurbishment works until completion.

Operation is the sixth stage after (re)construction and the last stage of the framework, which implies the use of the building and its maintenance plan so that its lifespan can be extended to the maximum.

At the supply chain level, the information available from digital building logbooks, integrating building renovation passports, smart readiness indicators, level(s) framework assessments, and EPCs should be accessible and updated across a building’s lifecycle and to all stakeholders to enable collaboration and their adequate management and to set guidelines and reclaimed products platforms (S3, O3, P5, Table 1). These transversal solutions also include training initiatives (O7, P5, and Table 1) through Cohesion Policy Funds and the Just Transition Fund [2], and reinforced technical assistance and adequate financing and funding through the RRF [2], to complement the European Local Energy Assistance as this is a priority for national recovery plans.

In conclusion, the newly developed Circular Refurbishment Framework presented here enables the creation of a collection of feasible solutions by identifying points of This framework connects building mapping, selective disassembly practices, (re)design, and (re)construction processes and presents opportunities for policy-based incentive implementation. Although it has the potential for broad application in EU refurbishment procedures, the Circular Refurbishment Framework can also be adapted to fit the specific context of individual countries