The environmental sustainability of buildings is founded on a better design of the building structures, of the thermal insulation, on the choice of better window frames and on the control of natural ventilation. The aim of a more accurate design could be the “passive house” or – at a lower level – the “low energy consumption” building. In the second case, the choice of the more suitable HVAC plant and also the accurate study of the air distribution in the environment become a need to complete the project in the direction of the energy saving. The renovation of a building edified in the sixties was analysed by energy performance simulation software. The results permit to identify better ways to operate for the restoration of typical Italian residential constructions of those years. The appropriate solutions to improve the reduction of thermal losses have been evaluated together with the integration of a more accurate design of the HVAC system. The calculations allow to determine more suitable choices related to the HVAC control systems and their set-points. By analysing the results, given as electrical and thermal annual energy consumption for each component, it is possible to determine their reduction.