Improving building energy performance is a fundamental strategy for reducing fossil fuel consumption, decreasing greenhouse gas emissions, and enhancing environmental sustainability, particularly in cold climates where space heating accounts for a major share of annual energy demand. In such climates, the thermal characteristics of the building envelope have a direct influence on heat loss, heating loads, and overall energy efficiency. Office–military buildings are of particular importance because of their long operating schedules, operational sensitivity, security requirements, and need for stable indoor thermal comfort. Therefore, optimizing the envelope of these buildings can contribute not only to energy conservation but also to operational sustainability and energy security. This study evaluates the energy performance of an office–military building located in the cold climate of Tabriz, Iran, and optimizes its envelope design parameters using a genetic algorithm.
In this research, a reference building model was developed and simulated under the climatic conditions of Tabriz using EnergyPlus through the JEPlus interface. The optimization process was performed in the JEPlus+EA environment, which allows dynamic building energy simulation to be integrated with evolutionary optimization techniques. A genetic algorithm was employed due to its capability to address complex design problems with multiple interdependent variables and to search efficiently for near-optimal solutions. The main objective of the optimization was to minimize annual natural gas consumption for space heating while maintaining acceptable indoor thermal conditions and considering practical architectural constraints.
The optimization process considered several envelope-related variables, including building orientation, window-to-wall ratio on the main façades, glazing configuration, glass layer characteristics, cavity properties between glazing layers, cavity gas type, and the geometry of the south-facing shading device. These variables were selected because they affect solar heat gains, conductive heat transfer, thermal losses through transparent surfaces, and the overall response of the envelope in a heating-dominated climate. Rather than examining each parameter separately, the study adopted an integrated optimization approach to evaluate the combined effect of envelope parameters on building energy performance.
The simulation and optimization results showed that improving the envelope configuration can significantly reduce heating energy demand. Annual natural gas consumption decreased from 1573 m³ in the base-case model to 1358 m³ in the optimized model. This reduction corresponds to an annual saving of 215 m³ of natural gas, equivalent to a 13.7% decrease in heating energy consumption. The optimized configuration demonstrated that the simultaneous adjustment of opaque and transparent envelope parameters can effectively enhance thermal performance and reduce heat loss under the cold climatic conditions of Tabriz. The results also emphasized the importance of transparent envelope design and solar-control strategies in achieving better energy performance.
A comparison of glazing scenarios further confirmed the strong influence of window type on heating energy consumption. Under identical optimized conditions, the use of single-glazed windows resulted in an annual natural gas consumption of 1616 m³, while the use of double-glazed windows reduced consumption to 1358 m³. Accordingly, double glazing achieved an annual saving of 258 m³ of natural gas and improved the thermal performance of the transparent envelope by approximately 16% compared with single glazing. This result indicates that reducing heat transfer through windows is one of the most effective strategies for improving the heating performance of buildings in cold climates. In addition, the analysis of the gas type within the glazing cavity showed that replacing air with argon reduced annual natural gas consumption from 1370 m³ to 1358 m³. This change provided an additional saving of 12 m³ per year, corresponding to approximately a 1% improvement in thermal performance.
From an environmental perspective, the reduction in natural gas consumption led to a decrease of 408.5 kg in annual CO₂ emissions, corresponding to a 13.7% reduction compared with the base-case model. These findings demonstrate that genetic algorithm-based optimization of building envelope parameters can be an effective method for reducing heating energy demand and associated environmental impacts in office–military buildings located in cold climates. The proposed approach provides a practical decision-support framework for architects, engineers, and energy planners seeking to improve energy efficiency, operational sustainability, and environmental performance in similar administrative, institutional, and military buildings.
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