Problem Statement :
With its towering walls and extraordinary architecture, the Bam Citadel was not merely a military fortress but a complete city encompassing all the elements of a vibrant and dynamic society. From prosperous markets and spiritually uplifting mosques to simple and luxurious houses, every component testifies to the lively existence of people who once lived within these walls. Once a center of commerce and culture, the citadel today stands as a symbol of the resilience and grandeur of Iranian history. Since Bam Citadel was constructed using traditional materials such as adobe and palm wood, the significance of utilizing sustainable and local materials in its construction becomes particularly evident. Building with compacted earth is an ancient technique that is valuable not only culturally but also environmentally. Due to its high thermal mass, this method stabilizes indoor temperatures and reduces the energy required for heating and cooling. The materials used in Bam Citadel possess low embodied energy, meaning that the energy consumed for extraction, processing, and transportation is significantly lower than that required for modern materials such as concrete and steel. Furthermore, the use of earth and local materials reduces the project’s carbon footprint and ensures climatic compatibility. Given the unique characteristics of Bam Citadel and the climatic and geographical conditions of the region, a comprehensive and precise study of the thermal, mechanical, and environmental performance of such structures from a regional and indigenous perspective is highly important. Recent studies adopting broader approaches have examined the impact of various additives, construction techniques, and climatic conditions on the performance of earthen materials. These investigations demonstrate that additives such as fly ash, natural fibers, and industrial waste materials can improve mechanical resistance and thermal behavior while preserving environmental sustainability. In recent years, increasing attention has been directed toward traditional architecture, particularly earthen structures, due to their environmental characteristics and favorable thermal performance. Research indicates that structures such as rammed-earth walls, especially in hot and humid climates, can effectively regulate indoor temperatures without the need for mechanical heating and cooling systems. Additionally, the use of indigenous materials and climate-responsive design strategies can provide thermal comfort during most days of the year. These characteristics have made traditional earthen architecture not only environmentally sustainable but also highly energy efficient and therefore suitable as a model for contemporary architectural development in hot and arid regions. Research Methodology Building energy simulation processes first emerged after the oil crisis of the 1970s. Over recent decades, these processes have been implemented through diverse computer systems that utilize advanced mathematical processing and graphical visualization capabilities. Today, numerous building energy simulation software packages—both commercial and free—are available. Since 1996, the United States Department of Energy has maintained a list of approximately one hundred computational tools while also developing several open-source software systems. For importing climatic conditions into the simulations, a valid EPW weather file for the city of Bam was downloaded from the official EnergyPlus Weather Data database of the U.S. Department of Energy. This file includes hourly data on temperature, relative humidity, solar radiation, and wind speed throughout an entire year and served as the primary climatic data source for the present study.
To verify and validate the data, the outputs of this file were compared with data generated by Meteonorm software. The comparison demonstrated that temperature and solar radiation trends in both datasets were similar, and discrepancies remained within acceptable ranges. Therefore, the EnergyPlus file was used as the primary dataset, while Meteonorm data functioned as supplementary and validation tools. Several scenarios involving variations in internal loads, natural ventilation, and the presence or absence of shading devices were designed and implemented to analyze the thermal behavior of the spaces throughout the year.

Research Objectives
To evaluate the capability of the traditional form and materials of Bam Citadel architecture in providing thermal comfort without mechanical systems. To measure the reduction of daily and seasonal temperature fluctuations within interior spaces and assess the role of indigenous materials such as adobe and palm wood in this performance. To analyze evidence obtained from energy simulations in DesignBuilder in order to confirm the passive and sustainable performance of traditional architecture in reducing energy consumption.

Research Questions
1. Are the form and materials employed in the traditional architecture of Bam Citadel capable of providing thermal comfort in a hot and arid climate without mechanical systems?
2. To what extent are daily and seasonal temperature fluctuations reduced within the interior spaces of Bam Citadel, and how dependent is this optimization on indigenous materials such as adobe and palm wood?
3. What evidence do DesignBuilder energy simulations provide in support of the passive and sustainable performance of traditional buildings in reducing energy consumption?

Conclusion
The present study employed building energy simulation in DesignBuilder software to examine thermal comfort conditions and energy consumption in Bam Citadel as a prominent example of traditional architecture in Iran’s hot and arid climate. Simulation results demonstrated that indigenous materials such as adobe and palm wood, together with appropriate spatial design, play a substantial role in regulating indoor temperature and reducing cooling loads. The simulations further revealed that although the local materials used in Bam Citadel—raw adobe and palm wood—cannot independently provide complete thermal comfort according to international standards, they significantly contribute to reducing indoor temperature fluctuations and decreasing cooling and heating demands. Therefore, these materials should be regarded as effective climatic solutions for improving energy efficiency in traditional buildings and as inspirational models for sustainable contemporary design. The findings indicate that the architectural design of Bam Citadel, relying on indigenous materials such as adobe and palm wood and a compact geometric form, succeeded in providing an acceptable level of thermal comfort during warm seasons despite the absence of active mechanical systems. DesignBuilder simulations revealed that indoor air temperatures frequently remained within the comfort range defined by international standards, while the severe temperature fluctuations characteristic of Bam’s hot and arid climate were significantly moderated within the building. This favorable thermal performance, especially during peak heat hours, demonstrates that traditional Iranian architecture was intelligently adapted to climatic conditions. Moreover, dynamic analysis of energy consumption showed a substantial reduction in the need for mechanical cooling, highlighting the remarkable capacity of passive strategies for energy control. Ultimately, by providing quantified evidence regarding the thermal performance of a traditional structure, this research strengthens the scientific position of energy analysis in historical architecture and paves the way for similar comparative studies in other traditional contexts.