It is important to search for substitutes for chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs) with a desirable combination of physical properties to meet the needs of specific applications, but ultimately with no harm to the environment. Therefore, a method for the computer-aided design of CFCs or HCFCs is proposed that is mainly based on the solution of a combinatorial problem according to the law of chemistry for a chosen set of functional groups, excluding the chlorine atom, to end up with the generation of molecular structures. Alternatively, the opportunity is also taken to explore binary mixtures between certain generated refrigerants themselves or with other chosen hydrocarbon compounds since pure fluids may have favourable properties when mixed together. The great ability and importance of group contribution methods in the development of such techniques is also demonstrated, particularly for predicting vapour-liquid equilibria and other thermodynamic properties like enthalpy or entropy of generated systems with the use of models like UNIFAC.