Buildings account for over 40% of energy consumption in Europe, of which around 75% are not energy efficient. This illustrates the importance of obtaining sustainable development certificates for both newly-developed and existing buildings. Their energy efficiency is assessed based on modeling and energy simulations. However, so far, there has not been any analysis regarding the actual energy consumption of a building: what is the impact of the implementation of innovative systems, appropriate management, specifications and the expected level of the users' comfort on the building energy performance? These issues have been thoroughly addressed in the first study in Europe, conducted by Skanska, Go4Energy and Cushman & Wakefield, which analyzes office buildings in Poland.