In the energy performance of buildings, there is always a gap between the designed energy consumption and actual operation that is difficult to mitigate or close. This GAP can be positive or negative; in practice, it is usually negative because actual performance turns out much worse than expected. The cause can be erroneous simulations, poor construction methods or operational practices with devices as well as users not operating as expected. Thus, interventions along any of three fundamental life-cycle directions: design, build, operation can reduce this GAP. Usually the bigger gaps arise from numerous operational issues that deteriorate the performance, well beyond expectations. Recent studies in the field of energy efficient buildings have shown that ICT solutions, user behaviour and energy policy, considered as a whole process within an organization, can have a significant impact on building energy use. As a result, significant energy savings opportunities can be achieved by influencing the involved stakeholders, to adopt systematic energy management practices. The 4 year EU H2020 HIT2GAP project has identified that the gap can be reduced by optimizing the following: simulation-calibration, disaggregation, forecasting, building performance assessment, energy management, user behaviour, multiple set-point control, fault detection and diagnosis. The HIT2GAP project will deliver an open solution with analytic tools and modular services for commercial buildings. The paper describes the Energy Management (EnMS) module, within the HIT2GAP platform, which allows to build a systematic approach to Energy Management based on ISO 50001 standard. The ISO 50001 standard specifies detailed requirements for establishing the EnMS and improving the overall building energy performance. The HIT2GAP platform is currently being piloted in 3 building complexes in 3 countries in Europe and preliminary results will be presented.