This study presents a new approach for enhancing building energy performance by integrating the energy audit and simulation using DesignBuilder software on a university building located in Alexandria, Egypt. The approach aims to evaluate the existing buildings' energy performance, quantify and analyze the gap between design predictions and actual energy performance, and improve energy performance. The findings reveal that the validation of the simulated building with the measured data proves the accuracy of the simulation. Lighting control saves 1.11% of electricity with a 0.92-y payback period. HVAC operating pattern achieves a substantial 20.8% annual natural gas consumption saving with 7.2 and 2.21 y payback period for the automated and manual systems, respectively with 2.5 tons CO₂ emission reduction. Using the optimal annual operating schedule saves annually 20.88% of the total cooling and heating energy and achieves 365 thermally comfortable days.

Reducing cooling energy demand while achieving effective natural ventilation remains a key challenge in the design of buildings for hot-arid climates. Solar chimneys represent a viable passive strategy; however, their effectiveness is governed by complex interactions between geometric and operational parameters. To investigate this potential, scaled-down experimental model was constructed and tested under controlled conditions, and its results were used to validate the simulation model. Subsequently, a comprehensive parametric analysis involving 19,008 design alternatives was conducted, employing multi-objective optimization to explore trade-offs between airflow enhancement and cooling energy reduction. Sensitivity and correlation analyses identified chimney height, width (North–South), and window operability as the most influential factors, with regression models confirming strong predictive relationships with both objectives. Regression analysis showed high predictive accuracy for cooling energy (R² = 90.87%, test R² = 90.45%). The optimal designs featured chimney heights of 10.5–13.0 m, widths of 3.1–4.5 m (North–South axis), lengths of 1.1–2.2 m (East–West axis), window-to-wall ratio values between 0.45 and 0.80, and operable openings exceeding 76% on South and West facades. These configurations increased airflow rates from 1.15 m³/s to 2.67 m³/s and achieved cooling energy savings of 30–32% compared to the base case.

This study investigates the performance of solar chimney systems as a passive cooling solution for buildings in hot arid climates. A combination of experimental and computational simulations was employed to analyze the impact of various chimney size configurations on indoor air temperature and cooling energy consumption. Results demonstrated that the incorporation of a solar chimney reduced mean indoor air temperature by up to 1.53 ℃ (5.3%) compared to the base case without solar chimney and achieved a 3% reduction in energy demand over the summer period. Among the 25 configurations tested, the optimal design, featuring a width of 38 cm and a height of 155 cm, achieved the best performance. This design also demonstrated scalability, with a width-to-height ratio of 1:4.08 and compatibility with typical room dimensions. Computational Fluid Dynamics (CFD) analysis validated the improved airflow dynamics of the optimized configuration, highlighting its potential for enhancing natural ventilation. The findings underline the effectiveness of solar chimneys as a sustainable and versatile design strategy for improving energy efficiency and indoor thermal comfort in residential, commercial, and institutional buildings in hot arid environments.