This paper investigate the retrofit of a sample building located in almost all the climatic zones in Italy and designed according to different energy levels, e.g. the minimum energy standard, the nZEB standard and the international Passivhaus standard. The analysis was performed using the PHPP, an Excel-based tool which enables to calculate the energy performance of the retrofitted building and the corresponding economic viability according to the LCC (life-cycle cost) analysis, by considering the annuity of the initial investment + possible components’ replacements within the period of analysis and the residual energy costs after the intervention. Using a common price reference for all the energy efficiency measures, we implemented in PHPP an analytical calculation of the cumulated functions for both investment and energy costs in order to look for the cost-optimum of the different proposed solutions depending on project and climate. In particular, it emerged that the use of cool roofs in especially very warm locations would be advisable as well as of selective glazing, whilst in warm-temperate locations only lead to minor or no improvements. An interesting and promising variant is installing simple extract air ventilation systems instead of HRV, which provide very good results in the warmest locations. Future investigations could be using regional official pricelists due to the high variability of prices throughout Italy and analysing the results’ dependence on the model, in other words testing the validity of the results for bigger projects. Besides all, the EnerPHit standard (a special standard for Passivhaus retrofits) should also be investigated.