Office buildings are a major part of the non-residential buildings stock. In the modern society, high multi-storey buildings – skyscrapers – are a common sight in urban areas. The combination of the skyscraper’s building shape and the office building type gives us an interesting case, which is special from the perspective of the building’s energy efficiency, quality of the indoor environment and the status symbol – often manifested in the façade’s visual appearance – which the building represents. In the thesis I analyse the heating and cooling demand of an existing business skyscraper, based on different energy-efficient design measures on the building’s façade. For the calculation of the building’s energy performance I used the simulation program EnergyPlus. As it turned out, there is a huge potential in reducing the building’s heating demand with the energy efficient design of the façade. The reduction of the building’s cooling demand is on the other hand not so drastical. As shown in the results of the analysis, there is a great risk of increasing the building’s cooling demand with the inappropriate façade design strategy. Based on the analysis results of different energy-efficient design measures on the building’s façade, I chose the most optimal combination of measures from the perspective of the building’s energy performance. On this model I added a heat recovery ventilation system (which decreased the heating demand even more) and compared the results with the model based on the existing building and the Slovenian energy performance codes (PURES). Compared to the model based on the existing building, the final model decreased the annual cooling demand for 1 %, and the annual heating demand for 65 %. Despite the huge decrease in the building’s heating demand, the final model, with all the energy-efficiency measures, still consumes 49 % too much heating energy, according to the PURES building performance codes!