This article explores how adding insulation to walls in a hot, dry climate can improve a building's energy efficiency. By using a mathematical model, researchers found that insulating walls with polystyrene can significantly reduce fluctuations in indoor air temperature. Thicker insulation leads to better results, acting as a thermal barrier that prevents heat from entering the building. In arid regions, heat gain through walls is a major cause of overheating, making high-quality insulation crucial for maintaining comfortable indoor temperatures.