Historical complexes in towns and cities, as most prominent witnesses of the past, are important elements of culture. Building heritage is a non-renewable resourse and the best way to preserve it is through urban renewal. The principal goals of urban renewal imply the improvement of living and working conditions in towns and cities, while optimizing the exploitation of all available resources, from man-made physical structures to energy. This research focuses on the town of Trebinje as an urban complex with a preserved urban matrix dating back to the 17th century and contains the analysis of a typical local structure, for the purpose of identifying those principles of improvement of energy efficiency applicable in Mediterranean climate zones. The case study focuses on the building of the Museum of Herzegovina in Trebinje, which should also serve as a pilot project for the Trebinje town administration and the Ministry of Education and Culture of Republika Srpska, but also as a project that can be multiplied in the future.