Green buildings mitigate critical environmental challenges in informal settlements. By incorporating energy-efficient retrofitting and sustainable materials, they reduce urban heat island effects and improve air quality, which is vital in densely populated areas ( Karamanis et al., 2024 ; Nibagwire et al., 2025a, 2025b ). For example, retrofitting informal housing with solar-green roofs has been shown to lower indoor temperatures by 5˚C, decreasing cooling energy demand by 30% ( Lukinov et al., 2024 ). Additionally, green infrastructure such as vegetative roofs and permeable pavements can reduce flood risks by 40% by managing stormwater runoff ( Green et al., 2021 ). These strategies also contribute to climate mitigation, with retrofits potentially cutting CO₂ emissions by 35% ( Niamir et al., 2024 ), while preserving local ecosystems and enhancing urban biodiversity ( Jauhari, 2023 ).

The economic rationale for green buildings is equally compelling. Sustainable construction can generate 6 - 8 million jobs annually in developing countries by 2030, boosting local economies ( Canton, 2021 ). Low-income households benefit directly, achieving up to 60% savings in energy costs through energy-efficient technologies ( Ehimen et al., 2023 ). Property values in upgraded settlements also rise, providing long-term financial stability for residents ( Kamjou et al., 2024 ). Modular designs and localized material sourcing further reduce costs, making green solutions scalable and affordable. For instance, decentralized solar systems like BIPVGREEN require minimal maintenance and can be adapted using local labor and resources, lowering implementation barriers ( Karamanis et al., 2024 ).

Socially, green buildings enhance health, equity, and community resilience. Access to green spaces correlates with improved physical and mental health outcomes, particularly for vulnerable groups like children ( Parmar, 2024 ). Community-driven initiatives, such as participatory planning for green roofs or rain gardens, foster ownership and trust, as seen in projects in Tanzania and India ( Oates et al., 2024 ). Climate-adaptive designs also improve habitability; for example, flood-resistant housing in Bangladesh reduced displacement risks during monsoons ( Green et al., 2021 ). By addressing systemic inequalities such as gender disparities in access to infrastructure, green transformations promote inclusive urban development ( UN-Habitat, 2020 ).

Informal settlements, often characterized by inadequate infrastructure and a lack of essential services, pose significant challenges in urban areas, particularly in developing countries ( Dhakal, 2024 ). These settlements are home to over one billion people, with numbers expected to rise, highlighting the urgent need for effective interventions ( UN-Habitat, 2020 ). The following sections explore the key aspects of informal settlements, including their socio-economic implications, upgrading strategies, and the role of participatory planning. Informal settlements are marked by poverty, overcrowding, and limited access to basic services such as clean water, sanitation, and electricity ( Henn et al., 2024 ). Residents often engage in informal economic activities, which, while crucial for survival, lack job security and benefits associated with formal employment ( Venkanna & Sonba, 2024 ). Higher levels of community participation correlate with more resilient outcomes, fostering a sense of ownership and responsibility among residents ( Terdoo, 2024 ). Figure 1 shows that informal settlements exist in “a state of deregulation”, one where the ownership, use, and purpose of land cannot be fixed and mapped according to any prescribed set of regulations or the law.

The document includes diverse case studies from Ethiopia, Brazil, Cape Town, and other regions, providing a broad perspective on informal settlements and green building transformations. For instance the overall, the settlement detection analysis identified that informal settlement areas comprised 1720 ha of Cape Town in 2020, representing 0.7% of the city (246,100 ha) ( Cinnamon and Noth, 2023 ). Since Cape Town is a very large city by area, with municipal boundaries capturing many non-residential areas, further area analysis was conducted to examine informal settlement areas in comparison to formal residential land use.

As detailed in Figure 2 ( Cinnamon and Noth, 2023 ), the top 15 informal settlements in 2020 by total area in hectares in Cape Town, residential parcel data was isolated to determine the size in hectares of just the formal residential areas of the city (38,275 ha), which was added to the overall informal settlement area results for 2020 to calculate the proportion of all residential areas (formal and informal) considered to be informal at each year. It presents a ranked list of areas (in hectares) for the year 2020, with values ranging from 138.4 ha to 30.4 ha ( Cinnamon and Noth, 2023 ).

Residents often lack formal ownership or legal rights over the land they occupy, particularly in informal settlements. This situation leads to various challenges, including insecurity of tenure and conflicts over land use. In informal settlements, land rights are often categorized into ownership, use, control, and management, complicating the provision of public infrastructure and services ( Mesgar and Ramirez-Lovering, 2021 ). Many urban residents, especially in China, experience a lack of rights due to the absence of property ownership and urban household registration, which limits their access to public services and participation in community governance ( Guo et al., 2021 ). The absence of formal land rights can lead to disputes, as seen in Ambon City, where residents occupy land without clear ownership, often resulting in conflicts ( Matuankotta and Lakburlawal, 2022 ). While squatters may hold potential ownership rights, the legal system often fails to address their vulnerabilities adequately ( Hickey, 2022 ).

Access to basic amenities such as potable water, sewage disposal, electricity, and roads is often inadequate, particularly for marginalized populations in urban and rural settings. This deficiency is exacerbated by socio-economic disparities, governance issues, and infrastructural neglect. Urban poor face significant barriers to accessing basic services, with inequalities manifesting across different asset quintiles ( Kundu et al., 2024 ). In hilly regions of India, factors like income levels, literacy rates, and housing quality directly influence access to amenities such as piped water and waste management systems ( Patra et al., 2023 ). Inadequate infrastructure severely hampers social and economic development, affecting health and resilience ( Patra et al., 2023 ). Many informal settlements lack reliable access to electricity and sanitation, with a significant portion of residents relying on communal facilities ( Mutyambizi et al., 2020 ). Poor access to clean water and sanitation leads to health issues, particularly in slum areas where open defecation is common due to inadequate facilities ( Lenka, 2022 ).

Many residents are compelled to live in these settlements due to the lack of affordable housing alternatives, as evidenced by the significant housing backlog in South Africa, where 1.2 million families reside in informal conditions ( Makhaye et al., 2021 ). Overcrowding exacerbates health risks, with poor sanitation and inadequate access to basic services being common issues ( Putra et al., 2024 ). While informal settlements provide immediate housing solutions for many, they also reflect broader socio-economic issues that require comprehensive policy interventions. Addressing these challenges necessitates a multi-sectoral approach that includes sustainable urban planning and community involvement ( Marnane, 2021 ).

Retrofitting involves modifying existing infrastructure to enhance its resilience against climate change impacts. This approach is particularly effective in urban areas where a significant portion of buildings and infrastructure are already in place. Green retrofitting focuses on reducing the environmental impact of existing buildings by improving energy efficiency and reducing greenhouse gas emissions. Research highlights the importance of policy instruments and financial incentives in promoting green retrofitting. For instance, studies suggest that government subsidies, tax incentives, and low-interest loans can significantly encourage building owners to adopt green retrofitting measures ( Zhang, 2023 ). Additionally, the integration of green technologies, such as energy-efficient systems and renewable energy sources, can further enhance the effectiveness of retrofitting projects ( Chen et al., 2024 ).

Community-driven solutions are integral to building resilience against climate change impacts. These solutions are often tailored to the specific needs and context of local communities, making them more effective and sustainable. The Community-Based Climate Risk Resilience (CBCRR) approach has been successfully implemented in various regions, including Thailand and Indonesia. This approach emphasizes the importance of community and household-level actions in building resilience to climate change. For example, in Thailand’s Eastern Economic Corridor, the CBCRR approach has been instrumental in identifying empirical climate resilience actions that can be generalized to other vulnerable communities ( Tanwattana and Toyoda, 2024 ). Similarly, in Indonesia, local governments have played a crucial role in developing policies that support community participation and empowerment, leading to more effective climate resilience strategies ( Tanwattana and Toyoda, 2024 ).

Community-led initiatives have been particularly effective in addressing the unique challenges faced by marginalized communities. For instance, in Boston, communities of color have been at the forefront of climate preparedness and resilience efforts. These initiatives emphasize the importance of listening to community perspectives, engaging in community organizing, and advocating for policy changes to address systemic inequalities ( Rivera-Kientz et al., 2024 ). Similarly, in Nigeria and Senegal, locally-led adaptation initiatives have been recognized as vital components of national climate change adaptation agendas, highlighting the need for national and global support to advance effective local climate action ( Okeke, 2023 ).

Policy interventions play a crucial role in supporting retrofitting and community-driven solutions. Effective policies can create an enabling environment for the implementation of climate resilience strategies. Policy instruments, such as subsidies, tax incentives, and low-interest loans, have been shown to significantly enhance the adoption of green retrofitting measures. For example, in British Columbia, policy strategies and financial incentives have been instrumental in reducing embodied carbon emissions in the building sector ( Zhang, 2023 ). Similarly, in Indonesia, local governments have leveraged policy instruments to promote the development of disaster-resistant infrastructure and sustainable practices. In conclusion, retrofitting, community-driven solutions, and policy interventions are essential strategies for addressing climate change impacts. Retrofitting offers a practical approach to enhancing the resilience of existing infrastructure, while community-driven solutions ensure that climate resilience strategies are tailored to the specific needs of local communities. Policy interventions provide the necessary framework and support for the effective implementation of these strategies. By integrating these approaches, communities can build resilience to climate change impacts and work towards a sustainable future.

Table 1 outlines three key strategies for enhancing sustainability and resilience in buildings. Green retrofitting emphasizes reducing environmental impact by incorporating energy-efficient systems and green technologies. Community-driven solutions underscore the role of local perspectives and policy advocacy in fostering resilience, ensuring interventions align with community needs. Policy interventions leverage financial mechanisms like subsidies, tax incentives, and loans to incentivize green retrofitting and climate-resilient practices. Together, these strategies highlight a multi-faceted approach, combining technological innovation, community engagement, and policy support to advance sustainable building practices.

The construction sector is a significant contributor to global environmental challenges, including resource depletion, energy consumption, and greenhouse gas emissions. To address these issues, governments worldwide have implemented various regulations and policies to promote green building practices. These measures include setting standards, providing financial incentives, and creating tax breaks to encourage sustainable construction. Governments are pivotal in setting regulations and policies that promote green building practices. They can provide incentives, subsidies, and tax breaks to encourage the adoption of sustainable construction methods ( Rasa, 2023 ). For instance, the Building and Construction Authority’s (BCA) Green Mark Scheme in Singapore has been instrumental in driving environmental sustainability in the construction industry. This scheme sets clear standards for energy efficiency, water conservation, and environmental quality, ensuring that new constructions meet established sustainability criteria ( Mahmud et al., 2024 ).

Governments play a crucial role in promoting green building practices through the establishment of regulatory frameworks, the provision of financial incentives, and international cooperation. By setting clear standards, providing subsidies and tax breaks, and encouraging sustainable technologies, governments can create an environment where green buildings become the norm rather than the exception. Future efforts should focus on optimizing policy frameworks, enhancing financial support, and fostering international collaboration to achieve global sustainability goals.

The private sector plays a pivotal role in driving innovation and investment in green technologies and construction practices, essential for aligning with the Sustainable Development Goals (SDGs). Their involvement not only fosters economic growth but also enhances environmental stewardship through the adoption of sustainable practices. This response will explore the significance of private sector participation, the benefits of green construction, and the challenges faced in this transition. The private sector is increasingly engaging with SDGs, recognizing the potential for sustainable business models that align with environmental goals ( van der Waal, 2024 ).

Collaborative ecosystems involving businesses, researchers, and policymakers are crucial for accelerating the commercialization of green technologies ( Ngoc et al., 2024 ). Green construction practices reduce carbon emissions and resource depletion while improving project efficiency ( Nwaogbe et al., 2025 ). However, High upfront costs and regulatory barriers hinder the adoption of green practices ( Nwaogbe et al., 2025 ) and Solutions include strengthening policy frameworks, enhancing public-private partnerships, and providing specialized training programs to bridge skill gaps. While the private sector’s engagement in green technologies is promising, challenges remain in ensuring that these efforts translate into substantial impacts on sustainability. A more strategic integration of SDGs into core business practices is necessary for meaningful progress.

NGOs significantly contribute to raising awareness and educating communities about the benefits of green buildings, particularly in regions facing environmental challenges. They serve as vital intermediaries, disseminating information and promoting sustainable practices that enhance energy efficiency and reduce environmental impacts. This role is crucial in fostering community engagement and understanding of green building benefits. NGOs engage in knowledge diffusion, helping communities understand the importance of green buildings in combating climate change and promoting sustainability ( Elayah et al., 2024 ). Green buildings are associated with reduced operating costs, improved occupant health, and increased property values, which NGOs highlight to encourage adoption ( Baeroom et al., 2025 ). Despite their efforts, NGOs often face challenges such as limited resources and regulatory restrictions, which can hinder their effectiveness in promoting green building initiatives ( Parveen, 2024 ). While NGOs play a crucial role in promoting green buildings, it is essential to recognize that their impact can be limited by external factors such as government policies and market readiness. Addressing these challenges requires collaborative efforts among stakeholders to create a conducive environment for sustainable practices.

The effectiveness of strategies for transforming informal settlements green infrastructure (GI), technological innovations, and policy frameworks depends on local governance, economic conditions, and community engagement. For example, decentralized solar systems (e.g., BIPVGREEN) succeed in participatory governance contexts ( Oates et al., 2024 ), while weak institutions or limited funding hinder scalability ( Ndlangamandla and Combrinck, 2020 ). Similarly, community-driven initiatives require trust and cultural sensitivity to avoid failure ( Watson, 2009 ). This variability necessitates adaptive, context-specific approaches. Among these strategies, green infrastructure (GI) mitigates environmental risks in informal settlements by improving air quality, managing stormwater, and enhancing resilience. GI integrates natural systems (e.g., green roofs, rain gardens) to reduce runoff by up to 79% ( Godyń et al., 2024 ) and filter pollutants through vegetation. Defined as interconnected networks that sustain natural processes, GI components vary by ecological priorities and human interaction levels.

Figure 7 outlines the five essential components, each contributing uniquely to ecological sustainability and land management. Managed native landscapes prioritize the preservation and restoration of indigenous ecosystems, frequently including conservationists and local populations. Reserves are designated areas established by governmental or environmental entities to preserve biodiversity. Parks and open spaces offer recreational and ecological advantages, usually overseen by local authorities or park services. Working landscapes, including agricultural and forested areas, harmonize production with sustainability, necessitating cooperation among landowners, farmers, and politicians. Finally, recycled lands entail the recycling of deteriorated or abandoned places for novel ecological or community applications, sometimes spearheaded by urban planners and environmental organizations. Collectively, these components provide an integrated system that fosters environmental health, economic sustainability, and social welfare through collaborative initiatives among many stakeholders.

Table 2 highlights diverse approaches to achieving sustainability in construction by integrating green building. Comparative analysis of green building policy incentives and sustainability outcomes by Region/Country summarizes key policies, outcomes, and references for various regions. Singapore’s Green Mark Scheme and mandatory codes have enhanced energy efficiency, while China’s subsidies and penalties drive green building adoption. India uses tax incentives to promote green technology, and the UK leverages grants and green bonds to meet consumer demand. The US focuses on LEED certification, and the EU’s Green Deal Policy aims for carbon neutrality.

Economically, in Table 3 ( Qoraney et al., 2024 ) represents in reducing or replacing costly gray infrastructure. The reduction in cost between the two systems (informal settlement & green building) due to changes in the percent of the used GRs and this effect will be noticeable and clear with big values more than this mentioned one in the big areas as in this study, the used positive system is a local system with diameter “315 mm and 400 mm” so the cost of using the GI almost the same when 60% of the plot roof area is used as a GR also the generated runoff volume reduced by 72% than the concrete roof, as the compare with a positive system with pipe diameter up to 400 mm, significant cost reductions will be observed in large areas and extensive storm water networks with large diameters. In such cases, the cost of the positive system becomes significantly higher than the GI system due to the large diameter and depths of the network. Also, in the case study, the area is not big enough to declare the reduction effect between the two systems, but cost reduction still exists. For example, when 50% of the plot roof area is used as a GR, the cost reduction is 10%. The reduction in generated runoff volume was 64%, and when 30% of the plot roof area was used as GR, the cost reduction was 37%, and the reduction in generated runoff volume was 47%. Also, increasing groundwater resources, as most of the rainfall will be infiltrated via these elements, will reduce water treatment costs and the added value of the developed area.

Building Integrated Photovoltaics combined with urban greenery (BIPVGREEN) offers a transformative approach to enhancing energy efficiency and environmental quality in informal settlements. This integration not only generates renewable energy but also improves urban aesthetics, mitigates heat islands, and supports sustainability. BIPVGREEN systems utilize building surfaces for solar energy while incorporating greenery, which cools panels through shading and evapotranspiration, thereby increasing efficiency and reducing reliance on fossil fuels ( Karamanis et al., 2024 ; Wang et al., 2023 ).

Recent studies highlight the practical benefits of BIPVGREEN. For instance, a 2023 study found that solar-green roofs in low-income areas could lower indoor temperatures by up to 5˚C, reducing cooling energy demand by approximately 30% ( Lukinov et al., 2024 ; Mihalakakou et al., 2023 ). Similarly, a 2024 case from Brazil demonstrated that PV-integrated green walls produce electricity and decrease particulate matter pollution by 15%, improving air quality ( Karamanis et al., 2024 ). These systems support local materials and labor, fostering job creation and community involvement, which are vital for sustainability. In addition, vegetation on green roofs can increase PV module efficiency by about 2% in tropical environments, further boosting energy gains ( Kaewpraek et al., 2021 ). This integrated approach also offers environmental benefits such as stormwater management, urban heat island reduction, and biodiversity support, making it a comprehensive solution for green building design.

Figure 8 ( Dallas et al., 2020 ) illustrates how a Building-Integrated Photovoltaic Vegetative (BIPV) green roof combines solar energy production with green roof technologies. It works by regulating the surface temperature of PV panels; vegetation naturally cools the panels through shading and evapotranspiration, enhancing their performance. The green roof infrastructure includes layers for vegetation, growth substrate, soil erosion prevention, water drainage, root barriers, and waterproofing, creating a symbiotic system that improves photovoltaic efficiency and environmental quality. Despite its advantages, widespread adoption faces challenges such as financial constraints, limited technical expertise, and the need for community engagement. Implementing smart technologies can enhance sustainability by optimizing resource management and integrating renewable energy sources ( Billanes et al., 2025 ). Addressing these barriers through awareness and capacity building is crucial for maximizing the benefits of BIPVGREEN in informal settlements.

The transformation of informal settlements into green buildings is a critical challenge for urban development globally. Local governments play a pivotal role in coordinating resources and technologies to achieve this transformation. Participatory planning is a cornerstone of successful informal settlement upgrading. By involving residents in the planning process, local governments can ensure that the solutions are tailored to the community’s needs and aspirations. Research from Tanzania and India demonstrates that community-led housing initiatives, with appropriate state support, can significantly improve the quality of life for vulnerable populations. These initiatives often involve participatory planning approaches, which integrate local knowledge and community feedback into the decision-making process ( Oates et al., 2024 ).

Effective policy frameworks and governance structures are essential for coordinating resources and technologies in informal settlement upgrading. These frameworks should promote transparency, accountability, and stakeholder participation, ensuring that the upgrading process is both inclusive and sustainable. Local governments can effectively coordinate resources and technologies to transform informal settlements into green buildings by adopting a combination of participatory planning, innovative technologies, public-private partnerships, inclusive zoning, and robust policy frameworks. These strategies, supported by case studies from around the world, demonstrate the potential for creating inclusive, resilient, and sustainable urban environments. By fostering collaboration between governments, communities, and private actors, local governments can address the challenges of informal settlements and promote sustainable urban development.