The title of the research study is “Elia Apartments Complex – Study & Improvement of Energy Performance” and it was conducted by the students Avlogiari Gavriela and Zoumpouli Isavella-Angeliki under the supervision of Professor Aristides Tsagrassoulis during the academic year 2020-2021. Within the context of the research project and in relation with the necessity presented in the branch of architecture for continuous optimization and enhancement of the conditions in the interior as well the exterior of the buildings, we identify the topic of studying and upgrading the energy class of an existing building. In connection with the interest presented for relevant subsidy programs and the extent energy certifications for houses, blocks of flats and complexes have reached, Elia Apartments, a tourist accommodation complex in the historic and traditional village of Afitos in Chalkidiki, is chosen. In the first part of the research, the study and analysis of the existing situation is presented with drawings, pictures and explanatory diagrams, while next with the use of Κ.Ε.Ν.Α.Κ. programs and Design Builder, which are the main tools of the research study, the elements/data relating to the energy identity of the complex, are given. In the second part, considering the several peculiarities and needs of the building in relation to its function and use as a tourist accommodation complex, within the limitations of a traditional village, with the characteristics of a building complex, the advantages and disadvantages it presents on the whole, the aim of the research study is set, which is its improvement of, at least, two energy classes in comparison with its existing condition by proposing minor interventions and preserving at the same time the architectural identity of the given complex.