دانشگاه شهید بهشتی صفه 1683-870X 36 2 2026 05 22 Thermal Comfort in Vernacular Shavadans vs. Contemporary Above-Ground Rooms: A Two-Season Field Study in Dezful, Iran Thermal Comfort in Vernacular Shavadans vs. Contemporary Above-Ground Rooms: A Two-Season Field Study in Dezful, Iran 3 26 106784 10.48308/soffeh.2025.237689.1374 FA Faezeh Babaee Ph.D. Student, College of Fine Arts, Faculty of Architecture, University of Tehran, Tehran, Iran 0009-0007-5936-0632 Shahin Heidari Professor, College of Fine Arts, Faculty of Architecture, University of Tehran, Tehran, Iran (shheidari@ut.ac.ir) 0000-0002-2016-2256 Journal Article 2024 11 25 <strong>Background and Objectives</strong>: Shavadans—traditional underground spaces in Dezful, Iran—have long served as passive thermal spaces in a hot semi-humid climate. Despite their historical significance and recognised potential for moderating extreme temperatures, comprehensive two-season field studies comparing their thermal comfort performance with co-located above-ground mixed-mode rooms remain scarce.<br />This study aims to provide empirical evidence on how Shavadans perform in both summer and winter, determine seasonal neutral temperatures, and assess  their potential contribution to contemporary climate-responsive design.<br /><strong> </strong><br /><strong>Method</strong>: A two-season field campaign was conducted in ten Shavadans during winter (December 2022) and summer (July 2023). Air temperature, relative humidity, and air velocity were measured every three hours from 06:00 to 18:00 at multiple depths. Simultaneously, Level-3 adaptive comfort questionnaires were administered to residents, yielding in 422 valid responses (102 winter and 109 summer datasets for both underground and above-ground spaces). Linear regression of TSV–temperature relationships and the Bin Method were used to derive neutral temperatures and acceptable comfort ranges for each season and space type.<br /> <br /><strong>Findings and Conclusion</strong>: Summer results showed that Shavadans maintained significantly cooler indoor conditionsthan above-ground rooms. The neutral temperature decreased from 26.6 °C (above-ground) to 24.5 °C (Shavadan), and only depths greater than 5 m remained fully within the comfort range. The deepest zones (>7 m) were up to 16.1 °C cooler than the courtyard at peak heat, demonstrating the strong thermal buffering capacity of underground construction. In winter, both environments exhibited neutral or near-neutral conditions; however, the Shavadan maintained more stable temperatures and slightly warmer sensations due to its high thermal mass, with a neutral temperature of 23.1 °C compared with 22.5 °C above-ground.<br />Overall, Shavadans mitigate heat stress effectively in summer and provide stable thermal conditions in winter, while above-ground rooms offer slightly better comfort during the cold season. These findings deliver the first dual-season empirical benchmark in Iran and highlight the potential of hybrid underground–surface strategies for low-energy, climate-responsive architectural design. <strong>Background and Objectives</strong>: Shavadans—traditional underground spaces in Dezful, Iran—have long served as passive thermal spaces in a hot semi-humid climate. Despite their historical significance and recognised potential for moderating extreme temperatures, comprehensive two-season field studies comparing their thermal comfort performance with co-located above-ground mixed-mode rooms remain scarce.<br />This study aims to provide empirical evidence on how Shavadans perform in both summer and winter, determine seasonal neutral temperatures, and assess  their potential contribution to contemporary climate-responsive design.<br /><strong> </strong><br /><strong>Method</strong>: A two-season field campaign was conducted in ten Shavadans during winter (December 2022) and summer (July 2023). Air temperature, relative humidity, and air velocity were measured every three hours from 06:00 to 18:00 at multiple depths. Simultaneously, Level-3 adaptive comfort questionnaires were administered to residents, yielding in 422 valid responses (102 winter and 109 summer datasets for both underground and above-ground spaces). Linear regression of TSV–temperature relationships and the Bin Method were used to derive neutral temperatures and acceptable comfort ranges for each season and space type.<br /> <br /><strong>Findings and Conclusion</strong>: Summer results showed that Shavadans maintained significantly cooler indoor conditionsthan above-ground rooms. The neutral temperature decreased from 26.6 °C (above-ground) to 24.5 °C (Shavadan), and only depths greater than 5 m remained fully within the comfort range. The deepest zones (>7 m) were up to 16.1 °C cooler than the courtyard at peak heat, demonstrating the strong thermal buffering capacity of underground construction. In winter, both environments exhibited neutral or near-neutral conditions; however, the Shavadan maintained more stable temperatures and slightly warmer sensations due to its high thermal mass, with a neutral temperature of 23.1 °C compared with 22.5 °C above-ground.<br />Overall, Shavadans mitigate heat stress effectively in summer and provide stable thermal conditions in winter, while above-ground rooms offer slightly better comfort during the cold season. These findings deliver the first dual-season empirical benchmark in Iran and highlight the potential of hybrid underground–surface strategies for low-energy, climate-responsive architectural design. https://soffeh.sbu.ac.ir/article_106784_df199a7d31b18e4f9aab0eb705cf296b.pdf