The Synergy of Community, Government, and Circular Economy in Shaping Social Housing Policies

: Despite state efforts to enhance affordability, access to adequate housing, deemed a fundamental human right, remains a global challenge. Projections indicate a looming housing deficit affecting 1.6 billion people by 2025, necessitating an integrated approach aligning environmental preservation with housing development. Circular Economy (CE) principles are identified as instrumental in advancing sustainable Social Housing Policies (SHPs). A Systematic Literature Review (SLR) placed best practice documents establishing a positive correlation between CE principles and increased social housing supply. The circularly built environment is recognised for reducing waste, carbon emissions, and resource depletion. However, this research proposes a nuanced perspective, asserting that integrating CE principles addresses housing needs and fosters environmental sustainability, job creation, and economic growth. Crucially, community, government, and the circular economy emerge as pivotal actors in overcoming challenges inherent in SHPs. This study contributes significantly to the discourse on housing policies and sustainability, advocating for an inclusive and environmentally conscious approach to the global housing deficit.


Introduction
Housing policy is a fundamental instrument for addressing the needs of individuals and communities while fostering social equity.This is underscored by the New Urban Agenda's imperative for universal access to secure and affordable housing.This overarching framework encompasses legislative and regulatory facets, program implementation, resource allocation, fiscal policies, and investments in social housing (SH) [1].
Since social housing (SH) is the core concept of this paper, the authors define social housing as affordable housing for low-income families or people with difficulties in finding housing, owned and managed by the government or by non-profit organisations, for leasing or joining the property, based on defined government rules [2,3].However, challenges such as social inclusion, access to healthy housing conditions, economic improvement and the optimal use of natural resources must be addressed for adequate and permanent social housing.
Concerning public social housing policies, a nuanced distinction exists between housing and social housing policies (SHP), concentrating on affordable housing provision for low-income demographics.This necessitates government intervention, subsidies, and collaborations with private developers to establish and maintain affordable housing units [4].Local governance is pivotal in tailoring housing strategies to community-specific needs and liaising with higher-level authorities [5].Local governments play a critical role by providing funding, regulating land use, and collaborating with other stakeholders to increase the supply of social housing [6].
Nations traditionally restrict subsidised SH to disadvantaged groups facing financial constraints in accessing housing under market conditions.Despite states' political obligations to enhance housing access for all, particular European Union (EU) countries and developing nations opt for parallel supplies, facilitated by specialised private investors receiving financial support from governmental entities [7,8].
It is worth noting that these terms' specific definitions and scope may vary between different countries and contexts.The distinction between housing and social housing policy (SHP) may depend on certain regions' particular policies and programs.In this study, the authors understand SHP, based on the Resolution of the European Parliament of 21 January 2021, on ensuring adequate, energy-saving, and healthy housing; combating homelessness and fighting discrimination; promoting an integrated approach to social, public, and affordable housing; and ensuring the safety of legal claims and developing housing markets that promote social inclusion [8].
The prevalence of informal settlements, which provide shelter for approximately 1 billion people, ref. [9] highlights the urgent need for sustainable housing solutions.Recognising the fundamental right to adequate housing, the European Union integrates social policy requirements with employment support, social care adequacy, and the fight against social exclusion [4].
The Sustainable Development Goals (SDGs) are a set of global objectives to address social, economic, and environmental challenges to achieve a more sustainable and equitable future for all.The 17 SDGs further champion housing as an integral facet across seven objectives, particularly SDG 11, focusing on Sustainable Cities and Communities [10].
However, due to the ambiguous nature of sustainable development, the SDGs' uncertain future challenges their successful realisation.Refs.[11,12] suggesting that the future of the SDGs remains uncertain due to the vague and elusive nature of the concept of sustainable development.The lack of a clear-cut definition and the presence of various interpretations may hinder the proper understanding and implementation of the SDGs, posing a challenge to their successful realisation in the future [11,12].
The recognition of social housing policies' intersection with multiple SDGs varies across different countries and regions.In China, India, and Brazil, policy responses to informal settlements are shaped by intergovernmental relations, electoral politics, municipal finance, and civil society capacity [13].The implementation of SDGs in South American countries is influenced by domestic politics, institutions, and power relations [14].The COVID-19 pandemic has affected the implementation of SDGs, with a focus on integrating and achieving synergy among goals [15].The integration of national policies for compact, connected cities is explored in various countries, including China and India [16].
The European Union has implemented various policies to address social challenges like homelessness, migration, ageing populations, and accessibility [8,17].Approximately 75% of the European Union's buildings are not energy-efficient, which means they require renovation in order to reduce carbon emissions.This is particularly important in the residential sector [7].
China has countered housing challenges by initiating programs, including the Public Rental Housing (PRH) program, which has been in place since 2010 and provides regulated rents for low-middle-income urban households.However, local governments rely on non-governmental financing, leading to a transformative shift in PRH governance and accommodating 37 million people [18].
In India, housing strategies face limitations due to ineffective policies and financing despite diverse, affordable housing and rental initiatives.Delhi, with its 11 million population, grapples with homelessness, particularly among segregated communities and older adults [19,20].
African countries experience significant housing challenges due to rapid urbanisation, which has resulted in ambitious policies such as Ethiopia's mass housing projects and South Africa's recent focus on SH.Slum upgrading, a preferred option in many countries, is deemed cost-effective, socially acceptable, and more accessible than new housing developments [21,22].
Brazil's extensive SH program, initiated in 2007, has constructed six million housing units over approximately 11 years, evolving with political changes and socioeconomic conditions [23,24].Scholars call for continuous investment, policy evaluation, and sustainability integration to emphasise environmental sustainability.
After analysing scenarios for global SHPs, searching for best practice solutions is a way forward.The effectiveness of real cases can help find new solutions that can inspire new approaches in SHPs.The concept of 'best practice' emerges, defined as interventions consistently proven effective through rigorous research [25].
Based on [26], the context of SHPs, best practices encompass effective strategies, approaches, and policies aligned with specific topics: A sustainable approach to addressing SHPs requires integrating environmental preservation with new housing and stock recovery.The Circular Economy (CE) model promotes resource reuse and regeneration.It can reduce waste and carbon emissions, create jobs, and contribute to individual and planetary well-being when applied to the built environment.
The concept of the circular economy is centred on minimising waste and promoting sustainable use of natural resources.It involves designing more durable, reusable, repairable, and recyclable products to keep materials and products in circulation for as long as possible.Two current and practical concepts within this framework include (i) Circular Economy as a Systems Solution Framework, which addresses global challenges such as climate change, biodiversity loss, waste, and pollution, and (ii) Transition to a Circular Economy with Digital Technology, which facilitates the shift to a circular economy by leveraging virtualisation, dematerialisation, transparency, and feedback-driven intelligence.Both concepts underscore the necessity of transitioning to a more sustainable economic model and emphasise the significance of renewable energy, efficient resource utilisation, and the role of technology in enabling a circular economy [27][28][29].
By incorporating the principles of the CE into SHPs, it is possible to take meaningful steps towards a more sustainable and equitable future.This partnership can be seen in several ways, as outlined [33,34] The built environment has recently witnessed research exploring the potential of CE principles.However, the SH sector remains an area that requires further investigation, as emphasised by [33].This sector presents significant opportunities to establish circular resource flows in the built environment [33].
Studies such as [35,36] have proposed social strategies to address the challenges faced by SH.Moreover, the authors [33,34,37] have highlighted the significance of incorporating CE principles and social innovations into sustainable SHPs and research.
According to [33] study, adopting circular business models demonstrated in best practice case studies is crucial for implementing CE in the sector.Under this trajectory, this study aims to analyse best practice case studies of SHPs that incorporate CE principles and suggest potential solutions that can be adopted.
The principles of the CE play a vital role in promoting sustainable SHPs.To explore this topic, a Systematic Literature Review (SLR) was conducted to investigate how CE concepts are integrated into the best practice of SHPs.The central question driving this research is "How have circular economy principles been incorporated into social housing policies' best practices?".In order to answer this problem, the following related questions were considered: QP1-What do the selected Social Housing Policies' Best Practices (SHBP) propose about the following topics?The study raises questions about best practices and CE principles.It is structured into three phases: conceptualisation, Systematic Literature Review (SLR), and identification of sustainable housing policies' best practices.The SLR specifically focused on selecting housing and social housing policy documents, excluding considerations beyond the scope of policy space and public programs.
In conclusion, the main objective of this research is to propose a differential approach to the conventional view of SHPs.The challenge entails identifying strategies implemented in SHPs that incorporate principles of CE in practice.This work's crux lies in practical solutions to address the SH crisis grounded in reality rather than relying on top-down theoretical solutions.The focus is bottom-up learning and knowledge acquisition to discern what works in practice.

Literature Review Approach
Conducting Systematic Literature Reviews (SLRs) is essential in collecting evidence that meets specific eligibility requirements to address research questions.SLRs utilise explicit and systematic methods to minimise bias, making them the gold standard in research methodology.Table 1 has a protocol synthesising the systematic literature review process developed in this study.

Quality appraisal
The three reviewers assess the quality of papers, and the paper is included when approved by at least two.

Extraction and Reporting Data collection
During this stage, the eligible articles are thoroughly examined and analysed.Additionally, more sources and studies may be included at this point to ensure a comprehensive analysis.The data extraction corresponds to themes, environmental aims, proposals, and countries.

Results synthesis
Type of synthesis: Interpreting results from bibliographic analysis.
In addition to mapping, evaluating, and synthesizing existing literature to advance knowledge in a specific field, SLRs also have the capability to identify gaps and stimulate new research directions.These advantages enable researchers to obtain reliable and robust findings that can inform policy-making and decision-making processes.SLRs are therefore valuable tools for generating evidence-based insights.
This SLR aims to analyse existing literature to explore how academic contributors and professionals in the SH field have interpreted and applied the concept of CE.While this study acknowledges its limitations, such as relying on search strings, databases, and exclusion criteria, the authors are confident that it offers a comprehensive coverage of the literature.

Planning
A meticulous and unbiased review protocol was established to fulfil the research objectives.This protocol was crafted following the guidelines provided in the Cochrane Handbook for Systematic Reviews of Interventions, Version 6.4, 2023 [38], to ensure rigorous methodology.It entails a comprehensive explanation and rationale for the review objectives, intended research techniques, study inclusion criteria, and data extraction, processing, and synthesis methods.Adopting an SLR process further bolsters the evidence's authenticity and the outcomes' credibility.
In order to successfully carry out a comprehensive systematic review, it is essential to integrate strong data handling practices, effective project management methods, and trustworthy quality control systems.These components play a pivotal role in guaranteeing the review's comprehensiveness, precision, and dependability.By incorporating these strategies, researchers can confidently navigate the review process and generate outcomes of exceptional quality [38].The Cochrane Handbook for Systematic Reviews of Interventions, Version 6.4, 2023, served as the methodological guide for this study.Adhering to the established protocol, the initial step in conducting an SLR involved identifying the specific issues to be investigated and formulating a rationale for the chosen topic, as perceived by the authors.This step laid the foundation for the subsequent stages of the SLR process, ensuring a structured and purposeful approach to the review.
Transitioning to a CE in housing policies involves developing technological solutions and incorporating social value as a critical element.As such, exploring "How have circular economy principles been incorporated into social housing policies' best practices?" is an essential step towards ecologically correct, socially fair, economically viable, and culturally appropriate solutions.
The research period was defined as 2000 to the present study time to ensure a comprehensive review.Only documents written in English were considered.Qualitative and quantitative studies within the scope of HP and CE were included in this review.

Proceedings
According to [39], researchers must have access to high-quality, relevant, accessible, and up-to-date information to ensure a comprehensive review.When conducting systematic reviews, the research period was defined as 2000 to the present study time.To ensure thorough coverage of studies, the researchers utilised information sources from three academic databases: the Web of Science from Clarivate Analytics, ScienceDirect, and Scopus from Elsevier.
Web of Science was selected as the preferred option because it encompasses all indexed journals that have an impact factor calculated in the Journal Citation Report (JCR).ScienceDirect, on the other hand, offered access to a wide range of international multidisciplinary studies.Lastly, Scopus provided extensive coverage of scientific journals, conference proceedings, and books on a global and regional scale.These choices were made based on the unique strengths and coverage areas of each database, ensuring a comprehensive and diverse collection of relevant sources for the review process [39].The filter applied to the databases was "type of documents", choosing all documents.

Analysis
The research methodology consisted of three distinct phases.Phase 01 aimed to understand the current state of research on housing and social housing policies, the circular economy, and best practices.The most frequently mentioned terms concerning SHP were housing policy, public housing policy, housing estate policy, affordable housing policy, low-income housing policy, and social housing policy.
Moving on to Phase 02, the focus was on conducting a systematic review.Concise inclusion and exclusion criteria for the documents were essential to carry out this process.Adopting the following criteria ensured a comprehensive search: all document types published from 2000 to the date of this research, availability in English, and complete text accessibility.
The search for housing policy/housing policies was combined with the best practice term to create three selection lists from different databases.Phase 02 is framed from Web of Science, 61 from Science Direct, and 532 from Scopus.The resulting 999 documents were processed in Microsoft Excel to eliminate duplicate articles and those without free access to the full text, leaving 960 valid documents.Four additional documents were also identified and cited in the bibliographic references, satisfying the pre-defined criteria for the initial research.The final selection resulted in 964 documents.Phase 02 is framed in Figure 1.The focus of the research shifted to Phase 03, which involved sifting through 964 documents on Housing Policies.Out of these, 335 were selected concerning SHPs; from that pool, nine were chosen based on best practice studies.In Figure 2, it is possible to see the partial list of the 964 documents on Housing Policies and the partial list of the 335 documents on SHPs.The nine documents on best practices are presented in the full version.After selecting the nine studies [40][41][42][43][44][45][46][47][48], they were organised into Results Matrices to facilitate the organisation of the findings.This technique employs a table format that presents research results clearly and concisely.The Results Matrix is particularly useful when dealing with extensive information, as it allows for easy visualisation and organisation of the data [49].It can also be viewed as an analysis since classifying and selecting information helps identify relationships between the findings [49].
In Results Matrix 1 (see Figure 3), the Excel document listed the nine documents by title and reference in column 1.This matrix addressed QP1, with the seven related topics guiding the search for data within each of the nine documents.Figure 3 is a print of the original Results Matrix 1, in which the authors made complete notes of the analysis.Results Matrix 2 (see Figure 4) features a list of nine documents identified by title and reference.Figure 4 aimed to address QP2, with the five related topics guiding the search for data within each of the nine documents.Similar to Figure 3, Figure 4 is an illustrative sample of the original table in which the complete notes made by the authors are included.

Results from the Systematic Literature Review
This chapter presents data and excerpts contributing to analysing the leading research question.In Phase 02, a selection of 964 documents was narrowed down to 335, focusing specifically on Social Housing Policies (SHPs).These selected documents provided insights into key themes and the geographic distribution of research in SHPs. Figure 5 visually represents the most frequently studied themes in this SLR.In a decrescent order are the most studied themes regarding SHPs: Market control, Homeless people, Social rental housing, General public housing programs review, Health equity, Gentrification, Community-led housing, Ethnic segregation, Secure of tenure, Migrants and Older people.Figure 6 showcases the top 10 countries with the highest research production in this area.Out of the 335 documents analysed, it was found that countries in the European Union produced 32% of the studies in this SLR.The EU nations devote 57% of their studies to the theme of segregation and its causes and implications, including poverty resulting from economic crises, migration, unregulated market control, unchecked gentrification, and ethnic prejudice.China collaborates with 30% of Asia studies, and Brazil represents 40% of the studies in Latin America and the Caribbean.Figure 7 illustrates the production by region.The present study constructed a graph visually representing the relationship between countries and their respective research themes.Figure 8 displays the ten countries in ascending order of the number of publications, each associated with its corresponding research theme.The green gradient on the graph denotes the number of publications from a particular country, with lighter shades indicating fewer publications and darker shades representing higher numbers.The selection of the 16 research themes was based on an ABC curve and encompasses 82% of the total publications analysed in this SLR.

Results from Result Matrix
The preceding section presented the findings of SHP studies and their respective focus areas.During phase 03, a refined selection process was implemented, identifying only those documents that simultaneously are SHP and best practice studies.Subsequently, each of the nine selected documents underwent a detailed analysis to provide answers to QP1 and QP2. that approximately 30% of the scrutinised documents explore strategies for regulating the housing market through legal means.These encompass optimising existing housing, regulating municipalities concerning zoning and land use laws, and providing incentives for mixed-use developments targeting middle and low-income citizens in urban areas.
Furthermore, Figure 5 elucidates additional themes such as renovating deteriorated housing, providing security in vulnerable residential areas, and offering shelter and health services to homeless individuals.The concerns expressed [8,17] align with the SLR results, emphasising themes like homelessness, migrants, older people, and accessibility in policy agendas.
The discourse on market control, especially in capitalist contexts, echoes the concerns articulated by [42,50,51] all converging on exploring alternative solutions to address housing decommodification.Inadequate regulations are identified as a catalyst for the unsustainability of lower-income environments in the centres of capitalist cities, resulting in forced relocations and subsequent gentrification.
The global economic downturn in 2008 not only escalated homelessness rates but also significantly contributed to gentrification, prompting a paradigm shift in housing policies globally [52].Housing policy failures are recognised as critical contributors to gentrification in regions like North America and Europe [38], exemplified by the neo-liberalization trend in the Netherlands leading to a decline in the social rental sector and spatial concentration of disadvantaged groups [53].
The impact of the global COVID-19 pandemic on housing policies is discerned globally, with Spain experiencing changes in demand and market recovery challenges [54].Despite governmental efforts to enhance housing affordability since the early 2000s, sustainable solutions remain elusive [55].Ref. [51] contends that housing policies, anchored in neoliberal affordability statistics since the early 1990s, have perpetuated inflation in house prices, exacerbating the challenges faced by prospective homeowners and rental occupants.
Figure 6 outlines the top ten countries investing significantly in the study of Social Housing Programs (SHPs), emphasising dedication rather than immediate success in implementation.A cross-sectional examination in Figure 7 reinforces the dominance of developed countries in SHP research, aligning with the UNCTADstat Data Center [56] distinction between developing and developed regions, where approximately 70% of the studies are attributed to the latter.
Turning to Figure 8, the focus shifts to China's challenges in fulfilling its recent public housing program, necessitated by the urbanisation strategy.Managing urban-rural population migration and addressing gentrification are prominent concerns, prompting efforts to control the real estate market and improve social transaction housing provision programs [18].
Examining Figure 8 reveals that in the United States, 76% of themes revolve around health equity, market control, and homelessness.The nuanced exploration of health equity underscores the interconnectedness of public health and housing policies, addressing diverse sub-themes such as COVID-19, economic crises, wars, children's health, older people, shanty towns, food insecurity, forced eviction, insecurity of tenure, and climate change.
The United Kingdom grapples with homelessness, prompting policymakers to consider strategies supporting reception programs and empowering homeless individuals.Australia, ranking fourth globally in SHP research, focuses on real estate market control while addressing the needs of diverse populations.Spanish studies accentuate the attention dedicated to housing cooperatives, emphasising project planning, user participation, mixed-social communities, and regulatory support at local and national levels.
In the Netherlands, regulatory efforts aim to prevent the segregation of minorities through financial policies supporting social rental programs.With approximately 60% of studies on public-private partnerships in SH programs, Brazil faces the challenges of insecure tenure and irregular housing.The global housing deficit, projected to impact 1.6 billion people by 2025 [57], disproportionately affects developing countries, including Brazil, Mexico, and Nigeria, which struggle with representation in academic publications.
In Latin America and the Caribbean, where 120 million individuals reside in substandard housing, the need for productive state-market partnerships to address housing access issues is emphasised [58].Italy's research focuses on ethnic segregation, market control, social rental housing, and post-disaster recovery, highlighting challenges in income and the resultant failure of social rental programs.
Sweden, facing issues of gentrification, lower incomes for social rent residents, and real estate speculation, necessitates government intervention in regulating financial schemes to support lower-income individuals.The limited development of alternative tenure forms in Latin America, notably in Brazil, is attributed to political changes and socioeconomic conditions, necessitating a long-term approach to effectively implementing SHPs.
The study sheds light on Nigeria's extensive research efforts, particularly in addressing homelessness, per the Australian Bureau of Statistics (ABS) definition in 2023 [59].Many nations express concern about the absence of housing market regulations, which leads to commodification and urban planning issues.Government intervention is proposed to mitigate socio-economic segregation and zoning challenges through financial support.Recent economic crises compound the situation's complexity, creating hurdles in effectively addressing housing concerns.

Proposed Framework for Integrating Circular Economy in Social Housing
In phase 03, a detailed analysis of nine social housing best practices cases based on selected documents was conducted.These cases were drawn from five continents: Europe, Oceania, North America, Africa, and South America.Although the sample size is not quantitative, it is noteworthy that sustainable housing best practices are being implemented worldwide.
Using Matrix Results 1 as a tool, the authors confirmed that six of the seven topics were defined by [26] effective strategies to promote SHP.The SHPBP's cases were privileged by housing supply and community engagement strategies.
The authors' purpose in preparing Figure 9 was to offer recommendations to deal with SHP issues seen as differentials.Strategies such as the government will facilitate the regulations and financial processes could be accomplished through streamlining licensing processes, reducing regulatory hurdles, and promoting mixed-use developments.Different approaches incorporated community-led housing strategies.The findings showed efforts to empower local communities to address their housing needs by actively participating in developing, owning, and managing homes.
When analysing Figure 10, it was possible to note that the CE principles regarding SHPs, based on [33,34]'s concept, that most appeared were Policy integration and Environmental Justice and Equity.In many ways, these principles were contemplated.The findings, in parallel, go hand in hand with the studied literature, which understands that without integration at the national and local level in SH provision, it is not possible to evolve on SHP issues.The relevance in finding the involvement of the Environmental Justice and Equity principle highlights the intrinsic role of the CE model in promoting sustainable solutions for the SHP's challenges.Differentials noted in the cases bring topics discussed in the study, such as "hands-on" contributions, improving environmental quality, and some approaches that enhance connections between different strategic actors.
Teodoro and Rayos Co (2009) [60] assert that the involvement of communities and their organisations is indispensable for the success of the housing sector.Community-led housing solutions are considered more suitable for addressing the needs and capacities of communities.Nevertheless, more than an exclusive focus on residents and their decisionmaking power in reconstruction initiatives may be required.However, [60] indicates that technical assistance and government support are critical for the long-term viability of the process.The government's role as a facilitator and protector is fundamental to the success of housing initiatives.Its unconditional support and openness to new realities establish local and national governments as critical stakeholders.
Despite the government's crucial role, the regulatory process is often complex and requires more effort.A convergence of Executive and Legislative Powers is typically needed to streamline the process.The intricacy of laws, the overlap of municipal, state, and federal legislation, the different interpretations of the various disciplines, negotiations, and technicians responsible for licensing in the departments, and the legal framework of laws, resolutions, and decrees present significant barriers to the cause [60].
Success in construction and urban development is contingent upon the robust support of public institutions at both national and local levels.To this end, the validation of new regulations, contract agreements, and financing proposals must be accompanied by the active participation of dwellers across all phases of the construction process.The authors of [50,60] explain that this includes their involvement in designing, hiring suppliers, and defining ownership and financing models.When residents themselves become involved in the definition of minimum layout standards, quality of materials, energy efficiency criteria, and the negotiation of agreements between public costs and protections for residents' financial possibilities-such as financing time, instalments, fees, and project management fees, they can preempt the detrimental effects of gentrification, abandonment, and depreciation of built environments.For these purposes, committees must be formed, comprising community and public authority representatives working in partnership.To ensure success, these processes must be apolitical and planned over the long term.
The research conducted by [8] highlights that there is significant variation in housing policies across the EU member states.Given the diverse social and economic contexts worldwide, more than a standard SHP may be required.While various actors such as the United States, United Kingdom, EU, China, and Australia provide guidance, the actual resolution of housing problems remains at the national, regional, or local level.
The findings are supported by [8]'s conclusion that housing policy should be tailored to individual countries' social and economic contexts due to their diversity.When it comes to user-centred solutions, the context of users' experiences is critical in understanding users' needs.
Furthermore, it is essential to consider the role of residents' labour in the incremental construction model, where the house still needs to be delivered finished, and significant work by residents is required to reduce construction costs, making the project feasible.However, to ensure the quality of the built environment and manage the budget effectively, public authorities must provide technical assistance and ensure quality control.
The Sustainable Development Goals (SDGs) provide a framework for addressing the five CE principles for SHPs.These CE principles are interconnected to some specific SDGs, and actions related to Figure 10 are responsible for these achievements.Following are some correlations: Analysing Figure 8 shows that the USA and the UK have similar interests in sustainable human progress (SHP), particularly regarding market control, homelessness, and health equity, which present challenges related to Sustainable Development Goals (SDGs) 1, 3, 5, and 10.
Meanwhile, European Union (EU) countries face distinct challenges in pursuing sustainable human progress.Reclaiming market control, closely tied to social inequality and economic integration, is multifaceted.These issues are directly linked to SDGs 1, 8, 10, and 11, emphasising the significance of their efforts.
In China, SHP development addresses the significant and ongoing national migration and floating population.While strides have been made in this area, effective planning through the decision-making process is crucial due to the sheer number of migrants.SDGs 11 and 17 are vital in meeting this demand.
Brazil is currently working on developing sustainable housing projects (SHPs) in order to avoid repeating past mistakes.The emphasis is on establishing effective partnerships to tackle the 5.876 million housing deficit and enhance 25 million essential aspects of housing [61], aligning with Sustainable Development Goals (SDGs) 8, 10, 11, and 16.
These are just a few examples of how SDGs are linked to principles of corporate social responsibility, focusing on promoting efficient responses from SHPs.It is important to note that these efforts must recognise SDG 13, as climate change poses an ongoing concern, and efforts to promote adaptation and resilience are delayed.
As the analysis progressed, it became apparent that a SHP proposal based on the CE model requires the involvement of three main actors: the community, the government, and the CE model itself.Each actor contributes essential points that help create the best solution for the case.The CE should be considered an actor since its performance is critical for balancing a sustainable SHP.
Figure 11 in the paper illustrates the tripod relationship between the three actors, highlighting their respective contributions.Based on an SLR of nine documents, the authors suggest an 'A ctors Contributions Tripod' to guide SHPs towards a sustainable future.
The authors argue that the community, the government, and the CE model all contribute uniquely to developing sustainable SHPs.By identifying these contributions, the authors believe policymakers can create best practices that address SH's challenges today.The bullets in the bubbles in Figure 11 concisely summarise the most relevant points highlighted in the study.
The study, however, did not include any case study concerning Topic 5-Inclusive building in its analysis, as shown in Figure 3.Although the reason for this omission is not explained, it must be noted that inclusive buildings are a crucial aspect of SHPs.With an ageing population and more advanced technical standards, ensuring accessibility for those with mobility issues is essential to promoting SHPs.

Conclusions
The present study sheds light on the significant role of CE in facilitating sustainability in the built environment.A comprehensive analysis of nine documents demonstrated that CE principles can effectively enhance the supply of SH.The findings underscore the importance of integrating CE practices into SHPs to promote sustainable development.The study was guided by specific objectives, which enabled the authors to address the main research question.
All nine cases, consciously or not, incorporated six of the seven strategies aligned with SHPs that encompass effective strategies, approaches, and policies.The topics that contributed to the success of the selected studies proposed some actions regarding affordable housing, housing affordability, housing supply, preventing homelessness, sustainable development, and community engagement.Regarding these topics, the focus was on community-led housing; government facilitating the regulations and financial processes; mixed-income neighbourhoods; and technical assistance institutes.
The results showed that all nine cases incorporated CE principles into SHPs, such as sustainable upgrades, balancing needs, policy integration, environmental justice and equity, and economic and social benefits.Based on these principles, hands-on contributions and environmental quality improvement were the primary efforts.
The analysis of the SHPBPs in this work highlights the significant interconnection of SDGs 1, 3, 5, 8, 10, 11, 13, 16, and 17, particularly in relation to CE principles and SHPs.It is important to recognise that efforts to promote SHP based on CE principles should consistently prioritise addressing SDG 13, given the urgent nature of climate change.There is an immediate need to expedite adaptation and resilience efforts as people continue to experience the daily impacts of human activities.The SDGs are closely aligned with the principles of corporate social responsibility, aiming to elicit effective responses from SHPs.
In response to the MQP, SHPBP has incorporated CE principles in their propositions by conciliating the contribution of three actors: community, government, and the circular economy.
In this sense, this study encouraged the authors to point out recommendations for the development of SHP based on the 'Actors Contributions Tripod':

Figure 2 .
Figure 2. Phase 03-Selecting the best practices from Social Housing Policies documents.

Figure 7 .
Figure 7. Distribution of Social Housing Policies Studies.
1. Affordable Housing: Increase affordable housing through policies like inclusionary zoning, density bonuses, and public-private partnerships for low to moderate-income families.2. Housing Affordability: Tackle housing affordability in high-cost areas with rent stabilisation, subsidies, and vouchers for low-income households.3. Housing Supply: Boost housing construction to meet demand by streamlining licensing, cutting regulatory hurdles, and promoting mixed-use developments.4. Preventing Homelessness: Implement plans to prevent and address homelessness, including housing support, rapid rehousing, and wrap-around services.5. Inclusive Housing: Make housing accessible and adaptable for individuals with dis-

Table 1 .
Systematic literature review protocol for this study.
Background to review Problem: Solve the inefficiency of SHPs based on CE principles.Rationale: CE principles are available to contribute to sustainable SHPs.Objectives Statement Primary objective: Recommend social housing policy strategies based on circular economy principles.Phase 01: Conceptualize housing policies.Conceptualize social housing policies.Point out what is best practice in SHPs.Point out which CE principles are involved with SHPs.Phase 02: Conduct SLR on housing policies and best practice.Phase 03: Based on the SLR results, select only SHPs among housing policies and identify the countries and the themes most cited.Based on the SLR results, select best practices related to SHPs.Based on the selected social housing policies' best practices (SHPBP), identify the actions proposed.Based on the selected SHBP, identify applied CE principles.Sub questions-Questions Problems QP1-What do the selected social housing policies' best practices propose about the following topics?Interventions, mechanisms, and outcomes: strategies, theories, practical examples, concepts, principles, guidelines, recommendations.Types of studies: both qualitative and quantitative.Search strategy for identification of studies Databases: ISI Web of Science, Scopus, and ScienceDirect.Timeframe: 2000 to the present time of the study.
Partnerships for the Goals; SDG 11: Sustainable Cities and Communities; SDG 13: Climate Action.Some actions, such as Favouring local service connections; Tightly connection among community, local and national levels.Decent Work and Economic Growth; SDG 1: No Poverty; SDG 3: Good Health and Well-being; SDG 10: Reduced Inequalities.Some actions, such as: Favouring local service connections; Improving environment quality; and Hands-on contributions.