Buildings in Denmark contribute to a large portion of the total energy consumption in the form of heating, ventilation and lighting. Therefore, improving the efficiency of the energy production and supply systems and enhancing the energy performance of buildings is indispensable to meet the ambitious Danish energy objectives. The current study provides an overall analysis of the energy performance of the Maersk office building located at the Odense Campus of the University of Southern Denmark, aiming to reduce the energy consumption and improve the overall energy performance. Energy Plus was employed to model the building and simulate the overall energy performance under the Danish conditions taking into account the construction topology, building envelope properties, HVAC systems, weather conditions and occupants behaviour. The 3D model of the building is created with Google Sketchup including 110 thermal zones, and Open Studio tool was used to establish the link between the 3D model and the Energy Plus simulation engine. Using the developed holistic energy model, an overall energy simulation for the Maersk office building was performed showing that the heating energy accounts for about 50% of the overall consumption while the other half is used in the form of electricity mostly for lighting, electric equipment and ventilation. A parametric study was carried out to assess the effect of various factors on the building overall energy consumption including the construction material, insulation, windows design and lighting, and various suggestions were provided. It was shown that replacing halogen lights in the corridors with LED lights would bring an energy saving of 144 GJ per year. In addition, using triple pane windows instead of the current double pane windows would save 60 GJ on district heating. In addition, various building envelope configurations were suggested so that the building envelope would comply with the Danish BR 10 regulation for existing buildings.