The article show the theoretical results obtained from an old laboratory building Technical University of Civil Engineering, Bucharest (TUCEB), heating and cooling system, retrofit, using renewable energy and natural (ecological) refrigerant. For simulations and analyses, were used PINCHLIGHT and REFPROP programs. Solar panels and a heat pump water-air were the main old equipments (old laboratory) used for solar energy and thermal energy. For retrofit the old laboratory were introduced new micro-channel heat exchangers (new laboratory) and was improved the refrigerant (was replaced R134a with R152a). Theoretical results will be implemented for retrofit TUCEB Environmental Pollution Laboratory.