The aim of this paper is to evaluate and illustrate the energy saving potential of the facade addition on existing and low energy performing block buildings in different climatic contexts. To achieve this purpose, the paper illustrates some outstanding case studies on deep renovation through facade and volumetric additions, as reference possible solutions towards energy renovation. To further assess the energy potential of these transformations, the same solutions have been applied to a reference building in Bologna. In particular, a selected apartment of typical building block has been investigated and simulated in detail, to identify the buildings' energy requirement and propose different retrofitting hypotheses towards nearly Zero Energy Buildings (nZEBs). Simulations of these different hypotheses resulted in corresponding diverse energy performances, from the very low grade of performance in "as built" scenario, up to nearly zero energy demand, for selected technological solutions applied in specific climatic contexts. To further estimate the energy impact the same apartment has been "extracted" from its original climatic context and energy simulations have been also carried out in two different climatic zones. Obtained results prove that facade additions are a very powerful solution towards the aim of zero energy in existing buildings. (C) 2018 Elsevier B.V. All rights reserved.