The historical headquarter of Italian Ministero degli Esteri (Ministry of External Affairs) in Rome named as "Palazzo della Farnesina" is a very large (about 700.000 m 3 of volume) and complex multi-functional building.The objective of present study, commissioned by Ministry of Environment, is to evaluate different energy saving strategies in this building achievable by the implementation of retrofit actions. At first, the seasonal energy consumption obtained by the existing cooling and heating systems has been estimated. Further, the aim was to evaluate the appropriate alternative technologies which contributes to lower energy consumption according with a non-intrusive building rehabilitation both with a more efficient plant, including various hypotheses of co-generation energy production and a desiccant cooling system. An extensive use of daylighting-control strategies have also been tested. Building energy performances have been assessed using DOE-2 simulation software. Allthe actions have been evaluated according to their economic, energy and environmental performances.