The dense activity in the FIP B Building makes energy optimization in the building very important because it will impact faculty operations. This research shows deficiencies in the design of the existing FIP B building, which can be corrected through a number of aspects of change based on field observation and Sefaira Simulation that can increase the building’s energy efficiency in the form of adding skylights, creating an atrium, and increasing the window-to-wall ratio. The value of increasing the efficiency of the new model compared to the existing one is known by the Sefaira energy performance simulation for both model envelopes. The results of the simulation show that the greatest increase in efficiency is in the use of AHU fans, the second is in AHU cooling, and the lowest is in interior lighting and equipment. However, lighting usage has the potential to be more efficient with the relatively improved daylight accessibility in the new design model. The overall annual energy use and EUI level in the new model are slightly more efficient than the existing model. The result of this study provides aspects of consideration in the architectural design of campus buildings with large masses.