Green renovation and multi-objective optimization of Tibetan courtyard dwellings

In plateau regions like Tibet, the cold climatic conditions persistent challenges for local building performance, while abundant solar energy resources enable low-carbon building retrofits. On the Qinghai-Tibetan plateau, many residents have enclosed their open courtyards with Courtyard Being Roofed (CBR) renovations to enhance indoor thermal comfort and increase temperatures. However, improper CBR implementation may compromise energy savings, worsen indoor light and heat environments, and lead to unnecessary financial burdens. This study analyzes CBR’s operational mechanisms, quantifies its performance trade-offs, and identifies risks under plateau conditions through a residential building case in Shannan City. Focusing on annual energy consumption (AEC), thermal discomfort hours (TDH), and initial cost (IC), we apply the NSGA-II algorithm and Artificial Neural Networks (ANN) to optimize CBR across conflicting objectives. The variables considered include courtyard dimensions, material properties, shading devices, and operational schedules. Sobol sensitivity analysis was employed to optimize these variables. Results show that, compared to the open courtyard, the optimal solution reduces AEC by 53% and TDH by 63%; compared to the actual retrofit scenario, it further lowers AEC by 10% and TDH by 39%, requiring only 47% of the implemented cost. Additionally, the study ranks the sensitivity of different parameters to these objectives, highlighting window materials and shading systems as critical factors. This research uncovers the complexities and contradictions of solar energy utilization in highland areas, providing a theoretical foundation and practical guidelines for courtyard dwellings in plateau regions and contributing to the sustainable development of Tibetan residential dwellings.

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