Windcatchers as a climate responsive design element in historic built form - A strategic tool for thermal comfort- adaptation to climate change - Case of Yazd, Iran

Authors

• Dhruma Bhavsar, Associate Professor, School of Architecture & Planning Woxsen University
• Piyush Pandya, Director, Ahmedabad World Heritage City Trust
• Ruchita Rana, Founding Partner, RMR Consultants ABSTRACT

Amidst escalating climate change and rising urban energy demands, traditional passive cooling systems offer valuable strategies for sustainable adaptation in the built environment. This paper examines the evolution of windcatchers-historic architectural elements originating in Iran and widely used across Asia and the Middle East-as a model for low-energy ventilation and thermal comfort.

Drawing on empirical knowledge from historic settlements, the study analyzes the design principles, performance, and cultural significance of windcatchers, highlighting their capacity to reduce indoor temperatures. The current paper aims to study the adaptability of these principles in modern context drawing lessons form contemporary practices.

CLIMATE CHANGE AND ASIA

In recent decades, the onset of the Anthropocene has made climate change an increasingly urgent global problem, affecting every country and continent. It now poses a clear and real threat to both natural environments and human settlements, with severe environmental challenges observed worldwide. Climate change impacts natural ecologies, urban and rural economies, daily livelihoods, and cultures, with consequences already significant and projected to intensify in the future (UNESCO, 2007). Changes to cultural heritage caused by climate change are inseparable from shifts in society, demographics, people’s behavior, and the impact of conflicting societal values and land-use planning, all of which must evolve in the face of a warming world (UNESCO, 2007). A major concern is that as the world warms, traditional thermal thresholds that have long guided safe thermal experiences in homes for 95% of the world’s population will be breached, making many homes too hot to occupy (Roaf, 1990). Adaptation strategies that focus on low-energy, sustainable solutions are thus a critical step in the right direction.

Across Asia, countless historic urban cores contain dwellings designed to provide comfort without mechanical systems. These empirical knowledge systems of climate-responsive design have long informed architects, helping reduce energy demand in new buildings and paving the way for a sustainable future. Historic buildings, especially residential types, offer valuable lessons for the present. Their development was closely aligned with local environmental and climatic conditions. Old settlements were carefully sited and designed to minimize the impact of harsh surroundings, demonstrating an approach that remains highly relevant today (Roaf, 1990).

LEARNING FROM THE PAST

Beyond tangible built heritage, another important cultural asset handed down through generations is the empirical knowledge system engrained within building traditions. This intangible heritage is deeply associated with the tangible built environment observed across historic precincts. Traditional architecture across Asia has always been based on the understanding of past generations regarding

climatic and ecological issues and how to address them to improve living conditions. These systems respected available resources, aiming for longevity, water conservation, and minimal maintenance. Such knowledge can still be used to reduce the large amount of energy wasted in modern buildings, where global trends often override local frameworks (Burton et al., 2005).

Historic buildings, especially residential typologies, teach us the importance of developing buildings and areas according to their specific environmental and climatic context. Old settlements exemplified this by developing at optimal locations to minimize environmental impact. Notable examples include the settlements at Yazd (Iran), the Potala Palace and its surrounding settlement at Lhasa (Tibet), and traditional stilt houses in Yawnghwe (Myanmar). These houses also incorporated the philosophy of minimal environmental disturbance, as seen in the mud Bhunga houses of Kutch (India) and the kath- khuni houses of Himachal (India). Historic houses prioritized stability and quality of construction, evident in the buildings of Patan and Kathmandu Valley.

Ancient builders designed for longevity and adaptability, as demonstrated by numerous adaptive reuse projects in cities like Ahmedabad (India) and Georgetown (Malaysia). Historic residential houses also prioritized occupant health, with designs in the humid environments of southern India and Sri Lanka allowing for free air circulation, a principle famously adopted by architect Geoffrey Bawa.

Builders in Jodhpur (India) used lime surkhi with antiseptic qualities, and historic houses consistently maintained a strong relationship between the built and natural environment.

TRADITIONAL WINDCATCHER AS A CLIMATE RESPONSIVE ELEMENT

One of the most significant legacies for climate adaptation is the windcatcher, also known as “Malqaf” or “Badgir,” a quintessential element of traditional and vernacular Iranian architecture. The windcatcher is a traditional Persian architectural device used to create natural ventilation and achieve thermal comfort in buildings. Similar examples can be found in the architecture of the Middle East, Pakistan, and India, reflecting the influence of Persian traditions (Roaf, 1982).

The historic city of Yazd, known as 'Shah-e-Badgirha' or the City of Windcatchers, provides an excellent example of windcatchers as passive cooling systems in a hot, arid climate. Houses in Yazd’s historic precincts feature compact designs with low wall surface-to-floor area ratios to decrease heat exchange through convection. Elements such as thick walls, courtyards, domes, covered pathways, and windcatchers are used as passive strategies to achieve thermal comfort. While domes, covered pathways, and thick walls reduce ambient air temperature, courtyards and windcatchers serve as primary sources of fresh air. Unlike the Western approach, where individuals control room climate, Yazdi residents select rooms based on their climate, taking advantage of the building’s range of thermal and airflow opportunities (Roaf, 2019).

Windcatchers are chimney-like structures built near house entrances, extending above the roofline to capture higher-altitude winds and channel them down to rooms below, often on the ground floor or basement. Constructed from mud bricks with clay and straw plaster, their openings are oriented according to prevailing wind and sun conditions. In Yazd, primary wind directions are from the north and east. During the day, wind movement creates positive pressure on the windward side, while hot south- and west-facing walls create negative pressure, generating constant airflow. At night, windcatchers operate via natural buoyancy, with warmer indoor air rising and being replaced by cooler outside air (Roaf, 2019).

Figure 1: Conceptual diagram of wind flow in a traditional windcatcher, illustrating the principles of passive ventilation and thermal comfort in Yazd houses (Source: Author).

There are various types of windcatchers in Iran, differing in the number of openings, height, shape, proportions, and internal divisions. Types include unidirectional, bidirectional, quadri-directional, hexahedral, and octahedral (multi-directional) windcatchers (Ghadiri et al., 2013).

An analysis of Yazd house sections reveals that features like courtyards with ponds, thick adobe and brick walls (up to 1m thick), and domes work together to moderate indoor climates. Courtyards with ponds humidify and cool incoming desert air, while thick walls provide high thermal resistance.

According to Roaf (1982), four-directional windcatcher towers are the most prevalent in Yazd,

comprising more than half of the city’s wind towers. Ghadiri et al. (2013) demonstrated through CFD simulations and validation with wind tunnel experiments that four-sided square windcatchers, particularly those with plus-form internal blades, provide the highest ventilation efficiency among the geometries tested. These systems can reduce indoor temperatures by 7.8°C to 10.7°C when outdoor temperatures reach 40°C, highlighting their effectiveness as passive cooling devices in Yazd’s hot, arid climate (Ghadiri et al., 2013; Roaf, 1982). Wind towers thus offer a robust alternative to modern, energy-intensive cooling systems like air conditioners. Small wind towers, developed before the ‘Little Ice Age’ of the 17th and 18th centuries, remain effective in today’s hotter climates and may be less vulnerable in a warming Yazd (Roaf, 2019).

Passive cooling techniques such as wind towers can be combined with evaporative cooling (e.g., wetted columns at windward openings) to further improve thermal performance, with temperature reductions up to 15°C possible by layering these methods (Bahadori, 1994). Other elements like courtyards, cavity walls, and north lights can enhance passive thermal comfort. However, comprehensive studies on the effectiveness of windcatchers under global warming, especially in Asia, remain limited. There is a need for scientific testing of vernacular traditions to understand how they can be upgraded for truly sustainable future buildings.

Figure 3: Analysis of wind flow patterns in the Teharina house, Yazd, based on a longitudinal section (Diagram by Author, adapted from Haji-Qassemi, 2005).

MODERN INTERPRETATIONS

Recent interpretations and contemporary adaptations of traditional windcatchers reflect a sophisticated synthesis of ancient passive cooling strategies with modern engineering, automation, and architectural aesthetics. Smart technologies, such as sensors and automated vent controls, are increasingly integrated into new windcatcher systems, enabling real-time adjustments based on wind direction, temperature, and indoor air quality to optimize performance without manual intervention (ArchDaily, 2021; Ugreen, 2024). In some cases, solar-powered fans are incorporated to enhance airflow during periods of low wind, ensuring continuous ventilation (Ugreen, 2024).

Geometrical and structural innovations have advanced, with research focusing on optimizing the number and configuration of inlet openings, as well as the cross-sectional shape of the shaft. Studies have shown that rectangular and hexagonal forms can improve airflow and distribution, while adjustable louvers and wing walls further direct and regulate air movement (Frontiers in Built Environment, 2025; ScienceDirect, 2020). Hybrid cooling techniques are now common, with windcatchers paired with evaporative cooling elements—such as wetted curtains or cooling pads—to achieve greater temperature reductions in hot, dry climates, and with heat pipes or helical coil exchangers in humid or cold regions (Jomehzadeh et al., 2017; ScienceDirect, 2020). Commercially available modular windcatcher products, featuring lightweight construction and multidirectional louver banks, facilitate integration into modern rooftops and align with contemporary design sensibilities (ArchDaily, 2021; Ugreen, 2024). Computational fluid dynamics (CFD) and other simulation tools are widely used to optimize windcatcher geometry and placement for specific

building layouts and environmental conditions, allowing for precise performance prediction and system integration (Frontiers in Built Environment, 2025; ScienceDirect, 2020).

Furthermore, windcatchers are being adapted for use in diverse climates and cultural contexts beyond their Middle Eastern and South Asian origins, with forms and materials tailored to local architectural traditions and environmental requirements (ArchDaily, 2021; Ugreen, 2024).

Table 1 : Mapping of key climatic and design challenges to corresponding architectural interventions and case studies in windcatcher adaptation. - ScienceDirect, 2020; Jomehzadeh et al., 2017

While windcatchers have proven highly effective in hot, arid regions such as Yazd, their performance is significantly constrained in non-arid or high-humidity climates. In humid environments, the potential for evaporative cooling—a key mechanism in traditional windcatcher operation—is greatly reduced, as the already moisture-laden air cannot absorb much additional water vapor. This limits the temperature drop achievable through passive means. Furthermore, the introduction of humid air into interior spaces can increase the risk of condensation and mold growth, potentially compromising indoor air quality and occupant health.

To address these challenges, adaptations such as integrating mechanical ventilation, dehumidification systems, or hybrid passive-active cooling strategies may be necessary. In some contemporary projects, windcatchers are paired with heat exchangers or desiccant-based dehumidification to maintain comfort in humid climates. However, these solutions often increase complexity and energy consumption, partially offsetting the sustainability benefits of purely passive systems.

Therefore, while windcatchers offer valuable lessons for sustainable design, their direct application outside arid regions requires careful consideration of local climatic conditions and may necessitate significant technological adaptation to ensure effectiveness and occupant comfort.

CONCLUSION

Windcatchers exemplify the successful integration of traditional wisdom and modern technology in sustainable design. Their evolution—from historic passive cooling systems in Yazd to contemporary, sensor-driven, and hybridized solutions worldwide—demonstrates their ongoing relevance for climate adaptation. As global temperatures rise, reimagining and scientifically testing these vernacular strategies will be crucial for creating resilient, low-energy buildings that respect both cultural heritage and environmental imperatives. As Ireland (2016) noted, “The most sustainable thing you can do is

not build new stuff.” Constructing new buildings demands 40% of global resources and generates a proportionate amount of waste (Burton et al., 2005). Thus, a major contribution to climate adaptation can be made by better utilizing existing infrastructure. In recent decades, many Asian cities have shifted toward high- and medium-rise buildings with wide roads for fossil-fuel-based mobility.

Adapting passive cooling elements like wind towers into the contemporary urban fabric is a challenge that must be addressed.

REFERENCES

ArchDaily. (2021, November 2). What is a traditional

windcatcher? https://www.archdaily.com/971216/what-is-a-traditional-windcatcher

Bahadori, M. N. (1994). Viability of wind towers in achieving summer comfort in the hot arid regions of the Middle-East. Renewable Energy, 5, 879–892. https://doi.org/10.1016/0960-1481(94)90108-2

Burton, I., Malone, E., & Huq, S. (2005). Adaptation policy frameworks for climate change: Developing strategies, policies and measures. Cambridge University Press.

Frontiers in Built Environment. (2025). Roadmap to developing a geometrical design guide for windcatchers. https://doi.org/10.3389/fbuil.2025.1534284

Ghadiri, M., Nik Ibrahim, N. L., & Mohamed, M. (2013). Performance evaluation of four-sided square wind catchers with different geometries by numerical method. Engineering Journal, 17(4), 9-18. https://doi.org/10.4186/ej.2013.17.4.9

Haji-Qassemi, K. (2005). Ganjnameh: Cyclopaedia of Iranian Islamic architecture. Volume 14: Yazd Houses (Part one). Tehran, Iran: Shahid Beheshti University, Faculty of Architecture and Urban Planning. https://doi.org/10.1088/1755-1315/1196/1/012103

Jomehzadeh, F., Nejat, P., Calautit, J. K., Yusof, M. B. M., Zakie, S. A., Hughes, B. R., & Muhammad Yazid, M. N. A. W. (2017). A review on windcatcher for passive cooling and natural ventilation in buildings, Part 1: Indoor air quality and thermal comfort assessment. Renewable and Sustainable Energy Reviews, 70, 736–756. https://doi.org/10.1016/j.rser.2016.11.254

Roaf, S. (1982). Wind Catchers, Living With the Desert. In E. Beazley (Ed.), Air & Philips. https://doi.org/10.5539/jsd.v3n2p89

Roaf, S. (1990). The significance of thermal thresholds in the performance of some traditional technologies. Proceedings of the North Sun Conference, Reading, Pergamon.

Roaf, S. (2019). 739: The Traditional Technology Trap (2): More lessons from the Wind catchers of Yazd, architecture.ucd.ie.

ScienceDirect. (2020). Windcatchers and their applications in contemporary architecture. Journal of Building Engineering, 32, 101070. https://doi.org/10.1016/j.jobe.2020.101070

UNESCO World Heritage Centre. (2007). Report on predicting and managing the impacts of climate change on World Heritage and strategy to assist States Parties to implement appropriate management responses.

Ugreen. (2024, March 2). Mastering the breeze: The comprehensive guide to

windcatchers. https://ugreen.io/mastering-the-breeze-the-comprehensive-guide-to-windcatchers/