Nowadays, it is very important the use of different technologies that reduce the energy consumption. This paper investigates the energy saving obtainable by using air conditioning systems provided with suitable earth-to-air (EAHX) and/or air-to-air (AAHX) heat exchangers, for two different Italian climates: Palermo, a city of Southern Italy characterized by hot summers and mild winters, and Milan, a city of Northern Italy characterized by hot summers and cold winters. A case study is analyzed

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... means of dynamic building energy performance software, with reference to the same designed office building with or without the two types of heat exchangers. The seasonal results show that in winter the AAHX reduces the energy requirement more than the EAHX, while in summer the EAHX is more effective. Yearly results show that the use of the EAHX is preferable in mild or hot climates. Moreover, basing on the seasonal results, the two technologies are combined (using the AAHX in winter and the EAHX in summer). The results show that the coupling of the two heat exchangers is more convenient for Milan (saving up to 74%) than for Palermo (59%). Finally, the CO2 emission reductions and discounted payback periods for the two technologies are evaluated.