Investigating the Impact of Thermal Insulation on Reducing Building Cooling Load Using Design Builder Software in the Hot and Humid Climate of Abadan

The hot and humid climate of southern Iran, particularly the city of Abadan, is characterized by intense solar radiation, high temperatures, and elevated relative humidity, making it one of the regions with the highest cooling demands in the country. Under such conditions, the building sector accounts for a significant share of total energy consumption, and heat transfer through the building envelope—especially walls and roofs—plays a major role in increasing cooling loads. The novelty of this study lies in the quantitative evaluation of the effect of rock wool thermal insulation on reducing the cooling load of a typical residential building in the hot and humid climate of Abadan using dynamic building energy simulation and actual climatic data. This issue has received limited attention, particularly under real operating conditions and during peak cooling demand periods. The aim of this study is to investigate the impact of thermal insulation on reducing building cooling loads in the hot and humid climate of Abadan using the Design Builder building energy simulation software. The case study is a typical two-story residential building with a total floor area of 445.38 m², modeled based on actual regional construction practices. To evaluate thermal performance, two scenarios were considered: (1) a building without thermal insulation in the external envelope, and (2) a building insulated with a 5-cm layer of rock wool applied to the walls and roof. The climatic data used in the simulations were based on actual weather conditions in Abadan. Simulations were conducted from June 5 to September 6, 2025, corresponding to the peak cooling season, with an hourly time step. Building operation schedules and cooling system set-point temperatures were defined within the thermal comfort range. The thermal properties of the building envelope materials, including thermal transmittance (U-value), heat capacity, and layer thickness, were specified according to commonly used local construction materials. In the insulated scenario, the only modification was the addition of a 5-cm rock wool insulation layer to the walls and roof, while all other parameters remained unchanged to ensure a reliable comparison. Simulation outputs, including total cooling load and hourly indoor temperature variations, were extracted and analyzed to assess the impact of insulation on the thermal performance of the building under hot and humid climatic conditions. The results showed that the total cooling energy demand of the uninsulated building during the study period was approximately 17,017 kWh, whereas the insulated building required only 7,830 kWh. In other words, the application of rock wool insulation resulted in a 54% reduction in cooling energy consumption. Furthermore, indoor temperature fluctuations were significantly reduced in the insulated model, leading to improved thermal stability. Based on these findings, the use of rock wool insulation is recommended as one of the most effective energy-efficiency measures for residential buildings in the hot and humid climate of Abadan.