Eco-regionalism1, as a new approach in sustainable architecture, emphasizes the coordination of design with the ecological, climatic, and cultural characteristics of a region. This research aims to provide a conceptual model for implementing the principles of eco-regionalism in sustainable design in the city of Birjand. Birjand, as a city with a hot and dry climate, provides unique opportunities to examine this approach. This study uses qualitative and quantitative methods, including the analysis of expert opinions, the review of case studies, and the evaluation of climatic and cultural data, to identify the key characteristics of eco-regionalism. The results of the research show that the use of local materials, the use of natural ventilation, water conservation through rainwater collection and the use of gray water, and the design of central courtyard houses are among the effective strategies in this approach. These strategies not only reduce energy and water consumption, but also correspond to the culture and needs of the local community. Furthermore, the examination of case studies such as the ancient city of Hadasar, Shabam in Yemen, and the village of Masouleh demonstrate the successful application of eco-regional principles in similar climates. This research suggests that by incorporating these principles into the urban design and architecture of Birjand, sustainable settlement patterns can be achieved that are both environmentally and culturally efficient. Ultimately, this conceptual model can be used as a guide for other cities with hot and dry climates and contribute to sustainable urban development.
Introduction
The escalating global challenges of climate change, resource depletion, and urbanization have underscored the urgent need for sustainable architectural practices. Eco-regionalism, a contemporary approach in sustainable architecture, advocates for designs that harmonize with the ecological, climatic, and cultural characteristics of a specific region. This study focuses on Birjand, a city in South Khorasan, Iran, characterized by a hot-arid climate and a rich cultural heritage rooted in traditional Persian architecture. The primary objective is to develop a conceptual model for implementing eco-regionalism principles in sustainable architectural and urban design, tailored to Birjand’s unique environmental and cultural context. By integrating local materials, passive design strategies, and culturally resonant solutions, this research aims to address the environmental challenges of hot-arid regions while preserving Birjand’s architectural identity. The significance of this study lies in its potential to offer a replicable framework for sustainable urban development in similar climatic zones, contributing to global efforts toward environmental resilience and cultural preservation in architecture.


Methodology
This research employs a mixed-methods approach, blending qualitative and quantitative methodologies to ensure a robust analysis of eco-regionalism in Birjand. Data collection involved semi-structured interviews with architects, urban planners, and environmental experts knowledgeable about Birjand’s architectural and climatic conditions. A comparative analysis of case studies from other hot-arid regions, such as Ghadames (Libya), Shibam (Yemen), and Masouleh (Iran), was conducted to identify best practices in eco-regional design. Quantitative data, including climatic parameters (temperature, humidity, solar radiation) and resource availability (local materials, water resources), were sourced from regional meteorological records, municipal archives, and environmental databases. The study also included an extensive literature review of eco-regionalism principles, focusing on sustainable material use, passive cooling techniques, water management strategies, and cultural integration in architecture. These data were synthesized to formulate a conceptual model that balances ecological efficiency with cultural and economic feasibility, ensuring applicability to Birjand and similar contexts.


Results and discussion
The findings indicate that eco-regionalism in Birjand can be effectively implemented through a synergy of traditional and modern sustainable strategies. The use of locally sourced materials, such as adobe and brick, was identified as a cornerstone of eco-regional design due to their low embodied energy and excellent thermal mass properties, which mitigate extreme temperature fluctuations in hot-arid climates. Passive design techniques, including courtyard houses, narrow shaded streets, and windcatchers (badgirs), were found to enhance thermal comfort, significantly reducing reliance on energy-intensive mechanical cooling systems. Water conservation strategies, such as rainwater harvesting and greywater recycling, address Birjand’s critical water scarcity, aligning with sustainable development principles. The comparative analysis of case studies revealed that similar strategies have been successfully applied in other hot-arid regions. For example, Shibam’s mud-brick towers utilize thermal mass and natural ventilation, while Masouleh’s terraced architecture optimizes land use and microclimate. These findings validate the proposed strategies for Birjand, where courtyard houses and shaded pathways resonate with historical architectural practices, fostering community acceptance. However, challenges include the higher initial costs of eco-friendly materials and the need for specialized training in sustainable design techniques. Additionally, the integration of cultural elements, such as traditional spatial configurations, enhances the social sustainability of the proposed model by aligning with local values and lifestyles. The study underscores that eco-regionalism not only reduces environmental impact but also strengthens cultural identity, making it a viable approach for sustainable urban development in Birjand.

Conclusion
This research proposes a comprehensive conceptual model for eco-regionalism in Birjand, integrating local materials, passive design techniques, water conservation strategies, and cultural considerations to achieve sustainable architecture. The model emphasizes a balance between environmental performance, cultural resonance, and economic viability, offering a blueprint for sustainable urban development in hot-arid climates. By drawing on traditional Persian architectural knowledge and modern sustainable practices, the framework reduces energy and water consumption while preserving Birjand’s cultural heritage. The model’s applicability extends beyond Birjand, providing a scalable approach for other cities with similar climatic and cultural contexts. Future research should focus on overcoming implementation barriers, such as cost optimization, scalability of local material production, and training programs for architects and builders to facilitate widespread adoption. Additionally, longitudinal studies could assess the long-term environmental and social impacts of eco-regional designs in Birjand, further refining the proposed model.