Today more then ever cities have a fundamental role not only from the design point of view but also from the social and economic one. In a century in which “urbanization” has a leading part, it is becoming more and more crucial to start toward a sustainable approach. Cities have to guarantee not only the quality of life for the inhabitants but also a low environmental impact which does not affect the needs of the future generations.
For this purpose, lot of cities in the world are reorganizing and rethinking themselves with the aim of becoming more smart and adapting to changes that could not be reversible. In an historical period in which buildings sector produces the main part of the global emissions and uses about the 40% of the energy source, the attention to the energy behaviour of the construction has assumed an essential importance. For existing buildings the energy simulation has two different advantages: to evaluate the current energy status and their improvement as a result of eventual interventions. Energy simulation has increasingly taken on a dynamic characteristic and
today is a valid tool to implement the existing built. Recently developed tools give the opportunity to estimate the energy behaviour of entire neighbourhoods and cities, giving the chance to evaluate the situation from a global and completely new point of view. The totalitarian approach and not focused on the single building, could be revolutionary and decisive for many cities that are not able to guarantee and pursue the goals regarding the sustainability.