In this work, predictive models for the solubility of gases in elastomeric polymers are evaluated. Such information is of interest, e.g. in the design of thermopane windows, where silicone rubbers and polyisobutylene (PIB) have been proposed as sealants. We found that very few models are suitable for polymer design/predictive calculations. A new model is therefore developed based on the Entropic-free-volume (FV) activity coefficient model in combination with Hildebrand solubility parameters (regular solution theory). Despite the simplicity of the approach, good results are obtained in many cases, provided that suitable input parameters, here the values of the hypothetical "liquid" volumes of the gases, are available. (C) 2003 Elsevier B.V. All rights reserved.