Urban informal settlements worldwide are increasingly vulnerable to the escalating impacts of climate change, particularly extreme heat events that severely compromise residents’ health and well-being. In these densely populated neighborhoods, often characterized by substandard housing with limited access to infrastructure and resources, mitigating heat stress presents a formidable challenge. Traditional cooling solutions, such as air conditioning, remain prohibitively expensive both in terms of initial investment and ongoing energy costs. This creates an urgent need for innovative, affordable, and easily deployable interventions that can provide effective thermal comfort in these settings. A new study conducted in Bihar, India, offers promising insights into how low-cost materials can help combat heat exposure inside informal dwellings, marking a significant step forward in climate adaptation strategies for vulnerable urban populations.
The study leverages a formidable dataset of over two million temperature measurements collected at one-minute intervals, allowing for a granular analysis of indoor thermal conditions across two distinct informal settlements in Bihar. Researchers employed two simple yet innovative interventions: the application of radiant foil inside homes and the use of Mylar blankets, both chosen for their reflective properties and ease of installation. The extensive data collection effort ensured that the results captured the subtle but vital dynamics of indoor temperature fluctuations over different times of day and environmental conditions, offering robust evidence on the efficacy of these materials in mitigating heat stress.
Radiant foils are thin, multi-layered sheets designed to reflect radiant heat, thereby reducing heat transfer through walls and roofs, which are typically constructed from metal or other heat-absorbing materials in informal settlements. By reducing the indoor temperature by an average of 1.24 degrees Celsius, the radiant foils demonstrated a meaningful ability to improve thermal comfort. This temperature reduction not only lowers the risk of heat-related illnesses but also enhances overall quality of life, especially for the most vulnerable groups such as children, the elderly, and those with pre-existing health conditions.
Mylar blankets, commonly used as emergency thermal blankets, were tested for their potential as an affordable heat mitigation strategy. These blankets, made from metalized polyester film, are reflective and lightweight, making them remarkably easy to deploy within existing structures. Despite achieving a slightly lower temperature reduction compared to radiant foils—an average decrease of 0.97 degrees Celsius—Mylar blankets still represented a significant improvement in indoor thermal conditions. Their widespread availability and low cost make them a highly scalable solution for informal settlements facing recurrent heat waves.
The implications of these findings extend beyond just temperature control. Heat stress in urban informal settlements contributes to increased morbidity and mortality rates, especially during peak summer months. By lowering indoor temperatures, these interventions can reduce the physiological strain experienced by residents, ultimately contributing to better health outcomes. Moreover, reducing the need for electricity-dependent cooling can also alleviate financial burdens and decrease greenhouse gas emissions, helping to address climate change through a synergistic approach that benefits both people and the planet.
An important dimension of this research is its focus on rapid deployability, a critical factor in informal settlements where residents often live in precarious conditions with transient housing. The modularity and lightweight nature of both radiant foils and Mylar blankets allow residents or aid organizations to implement the cooling solutions swiftly, without the need for professional installation or extensive structural modifications. This ease of deployment is crucial for emergency responses to heat waves, ensuring that vulnerable populations receive timely relief when heat events are most severe.
The researchers’ choice to study two communities in Bihar provides valuable contextual insights into the challenges endemic to Indian informal settlements, which are representative of many similar urban areas in the Global South. These communities are often deprived of basic urban services, with high population density and poor housing conditions exacerbating heat exposure. The study’s setting underscores the real-world applicability of the interventions and highlights the importance of context-specific adaptation solutions that resonate with local socio-economic realities.
This investigation furthermore underscores the transformative potential of combining rigorous scientific measurement with community engagement. By involving residents in the deployment and maintenance of the interventions, the project fostered a sense of ownership and awareness about heat risk mitigation. This participatory approach is essential for ensuring the long-term sustainability and acceptance of such interventions, as community buy-in dramatically increases the likelihood of adoption and continued use.
From a technical standpoint, the minute-level temperature data enabled a detailed comparative analysis of indoor heat dynamics before and after the installation of materials. This high-resolution monitoring revealed not only peak temperature reductions but also delayed heat gain, meaning homes stayed cooler for longer periods into the evening. This effect is particularly important because it enhances nighttime comfort, which is crucial for rest and recovery, especially in settings where outdoor temperatures remain elevated after sunset.
The study also contributes valuable knowledge to the broader discourse on climate adaptation in urban settings. While much policy attention has focused on large-scale infrastructure projects and high-tech solutions, this research reaffirms the critical role that low-tech, cost-effective interventions can play in safeguarding vulnerable communities. The findings encourage stakeholders—from urban planners to public health officials—to consider these strategies as integral components of heat resilience planning.
In addition to its practical outcomes, the research methodology represents a model for future climate adaptation studies. The combination of comprehensive environmental monitoring and on-the-ground intervention trials offers a replicable framework for testing low-cost technologies in varied geographic and social contexts. Such approaches are essential for scaling solutions globally and tailoring them to diverse urban informal settlements that share common vulnerabilities but differ in specific environmental and cultural conditions.
In reflecting on the implications of these findings, it is clear that tackling heat stress requires multifaceted strategies that integrate environmental science, material technology, social engagement, and policy innovation. The study’s success in demonstrating tangible indoor temperature reductions using accessible materials establishes a new benchmark for what is achievable in climate adaptation interventions in marginalized urban environments.
Looking ahead, there is potential for further optimization of these materials and exploration of hybrid approaches that combine reflective foils or blankets with passive ventilation enhancements or shading devices. Integrating these techniques could amplify cooling effects while maintaining affordability and ease of implementation, thus broadening the arsenal of tools available to vulnerable communities facing runaway urban heat challenges.
Ultimately, the research led by Ang, Sparsh, Wang, and colleagues offers a beacon of hope in the climate crisis, illustrating how ingenious, low-cost solutions can empower some of the world’s most vulnerable populations to better withstand the intensifying impacts of global warming. By translating scientific insights into practical, scalable improvements in human comfort and health, this work embodies the promise of climate resilience grounded in equity and innovation.
As urban areas continue to expand and climate threats escalate, the urgency of developing and disseminating affordable cooling interventions will only grow. This study provides a vital foundation and call to action for scientists, policymakers, and communities alike to prioritize accessible strategies that protect health and livability in informal settlements worldwide.
Subject of Research: Heat stress mitigation interventions for urban informal settlements in Bihar, India.
Article Title: Low-cost interventions for heat stress mitigation in urban informal settlements.
Article References:
Ang, Y.Q., Sparsh, Wang, T. et al. Low-cost interventions for heat stress mitigation in urban informal settlements. Nat Cities (2026). https://doi.org/10.1038/s44284-025-00370-3
Image Credits: AI Generated
