## 2 Materials and Methods
### Stages of Systematic Review Protocol
#### 2.2.1 Planning
\begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt}} \hline
**Protocol** & **Stages Protocol Steps** & **Research Aspects** \\ \hline Background to review & Problem: Solve the social housing crisis based on CE principles. & Rationale: Circular Economy (CE) principles are available to help solve the social housing challenge. \\ Initial RQ: How can the Circular Economy contribute to resolving social housing challenges? & Primary objective: \\
1. Planning & 1—Exploring the most-used terms related to SH and CE on an academic basis. 2—Selecting, through an SLR, documents that deal with SH and relate to CE principles. 3—Listing the study themes covered in SH studies related to CE. 4—Listing which Circular Economy principles have been addressed in studies on social housing. 5—Listing the main proposals made in the documents. 6—Identifying potential future gaps and opportunities to fuel the process towards a CE in the SH sector. \\ Objectives Statement & Sub-questions—Question problems: \\ QP1. Which themes related to the Circular Economy have been studied in social housing research? & QP2. Which Circular Economy principles have been addressed in studies on social housing? \\ QP3. How can the construction sector contribute to a Circular Economy model addressing social housing challenges? & QP4. What gaps remain in the relationship between social housing and the Circular Economy? \\ \hline \multirow{5}{*}{2. Processing} & Criteria for selecting studies & Context: social housing, social housing policies, circular economy, life cycle assessment, reused materials, recycled materials, refurbishment, material passports, designing for assembly, designing for disassembly, cradle-to-cradle, built environment, energy efficiency, sustainable urban development. \\  & & Interventions, mechanisms, and outcomes: strategies, theories, practical examples, concepts, principles, guidelines, recommendations. \\  & Types of studies: both qualitative and quantitative. \\ \hline \multirow{5}{*}{2. Processing} & \multirow{5}{*}{Search strategy for identification of studies} & Databases: Scopus, Web of Science, and ScienceDirect. \\  & & Timeframe: 2015 to the present time of the study. \\  & & Keywords: social housing, public housing, housing estate, affordable house, circular economy, circular material, cradle-to-cradle. \\  & & Language: English. \\  & & Article type: indexed journal papers, conference proceedings, books, book chapters. \\  & & Grey literature: included. \\ \hline \multirow{5}{*}{3. Analysis} & \multirow{5}{*}{Eligibility} & Inclusion/exclusion criteria: \\  & & - Journal papers, conferences, proceedings, book chapters, editorials, abstracts. \\  & & - Open access. \\ \cline{1-1}  & & - Social housing, public housing, housing estate, affordable housing, \\ \cline{1-1}  & & - Circular Economy, life cycle assessment/costing (LCA/LCC), circular material, \\ \cline{1-1}  & & - cradle-to-cradle. \\ \cline{1-1}  & & - 2015 to the time of the study. \\ \cline{1-1}  & & - Three reviewers screen the articles. \\ \hline \multirow{2}{*}{Quality appraisal} & \multirow{2}{*}{The paper is accepted only if approved by at least two of the three reviewers who assess its quality.} & \multicolumn{1}{p{113.8 pt}}{} \\ \cline{1-1}  & & & \\ \end{tabular}
\end{table} 
Table 1: Systematic Literature Review protocol for this study. The implementation of a Circular Economy in social housing requires the development of technological solutions and the integration of social value within the housing community. Both components are essential in achieving success. Due to this challenge, exploring \"How can the Circular Economy collaborate on the issue of social housing?\" seems to be an essential step on a long road towards ecologically correct, socially fair, economically viable, and culturally appropriate solutions. The period for this research was defined as 2015 to 2023. Only articles written in English were considered for this review. Qualitative and quantitative studies developed within the scope of SH and CE were considered for this review.