Problem Statement: Elements such as the Iwan have played a significant role in moderating climatic conditions in Iranian vernacular architecture. While previous research has predominantly focused on the performance of Iwans in the hot-arid climate of the Central Plateau, this study investigates the ventilative role of Iwans in the temperate and humid climate of Mazandaran.
Research Objectives: The aim is to conduct a quantitative comparative analysis of the natural ventilation performance of various Iwan types in historic Qajar-era houses of Mazandaran's plain region, thereby documenting indigenous environmental knowledge in this climate.
Research Method: This study employs a mixed-method approach combining historical research, case study analysis, and numerical simulation. Through library and field studies, 21 historic houses were identified. A selection framework was developed, resulting in four case studies (Kalbadi 2, Siyami, Ehtesham, and Taghavai). Three-dimensional models were reconstructed in DesignBuilder 2019. The ventilation performance of each building was analyzed under two scenarios—"with Iwan" and "without Iwan"—using Computational Fluid Dynamics (CFD) simulation under identical climatic conditions. A simulation error margin of ±5% was calculated based on validation with similar studies.
Conclusion: Results demonstrate that the presence of an Iwan significantly improves indoor ventilation, with the degree of improvement depending on its physical configuration and the number of open sides. The increase in Air Changes per Hour (ACH) is as follows: Siyami House (four-sided open Iwan): 83%, Taghavai House (four-sided open Iwan): 74%, Kalbadi 2 House (three-sided open Iwan): 63%, and Ehtesham House (one-sided open Iwan): 37%. The findings reveal that the relationship between the number of open sides and ventilation improvement is not linear. This research emphasizes that exterior-oriented Iwans represent an intelligent response to natural ventilation needs in Mazandaran's climate, with the peripheral veranda (Gholam Gardeshi Iwan) identified as the most efficient type.