Institutional buildings are very important considering the impact on energy consumption of a city. Due to the conditions of operation, the size and the density of occupants, institutional buildings represent a challenge to save energy in both cold and hot seasons. Urban climate influences the building performance, typically reducing thermal demand in winter and increasing in summer. The context is relevant in determining urban heat island effect, shadows, ventilation and in general the thermal environment that surrounds buildings. This paper develops a strategy to estimate the energy penalty obtained by including in building performance simulation the urban effects. Urban Weather Generator v. 4 beta and TRNSYS v. 17 tools are used to obtain base and urban energy demand through the whole year in three cases of study in Rome.