Integrating Building Information Modeling (BIM) with energy analysis supports the validation of sustainable rehabilitation strategies, offering benefits to building owners, stakeholders, and managers. This study presents a case involving a large commercial building, detailing the development of an energy-focused BIM model. Key steps included incorporating thermal and regulatory parameters into the design, assigning thermal characteristics to materials, generating an energy simulation model, and validating it using actual utility consumption data. The validation process guided design adaptations based on the building’s new functional requirements and enhanced thermal load assessments. The HVAC system’s performance was influenced by external heat gains, occupancy, and space typology. Comparative analysis of energy consumption and cost per square meter showed that the proposed rehabilitation scenario, adapted to new space usage, was less energy-efficient than the existing configuration. The modeling software offered strengths in user interface, component integration, and flexibility in adjusting energy parameters and space types. However, limitations in accurately representing real-world occupancy and space usage affected the model’s reliability, posing challenges in validating both existing and proposed energy scenarios. In summary, while BIM-based energy modeling provides valuable insights for sustainable retrofitting, current software limitations in simulating real conditions can hinder the accuracy and applicability of energy performance evaluations.