Microencapsulated phase change materials (MEPCMs) have the potential for energy storage applications in buildings. However, current MEPCMs are limited by their singular phase change transitional temperatures and are therefore unable to satisfy all year seasonal energy storage applications. This study was focused on numerically assessing the energy saving potential of a binary MEPCM drywall system which is capable of operating within two different phase change transitional temperature ranges. In this study, Ansys Fluent and the ESP-r simulation tools were employed because Fluent could offer a detailed quantification of the temperature changes within the composite drywall system and ESP-r has the capability of thermal modelling of phase change materials at whole building scale by using annual weather data as boundary conditions. The Fluent simulation results demonstrated that the thermal energy charge time and thermal energy charge/discharge amount of the binary MEPCM drywall were significantly increased when the MEPCM thickness increased from 1 mm to 5 mm, and the 5 mm thick layer had adequate capacity to balance the thermal energy during day and night. The ESP-r results showed that for the hot period in Hangzhou (China), the 5 mm thick binary MEPCM drywall was able to achieve a maximum peak air temperature reduction of about 6.7 °C and to increase the number of hours the indoor air temperatures were within the 21–28 °C range by about 12% in comparison with other drywalls. Experimental evaluation is therefore being recommended to verify the full practical potential of MEPCMs with two phase change temperature ranges.