The insulation value, evaporative resistance, and permeability index of 22 representative clothing ensembles (with and without the contribution of the air layer around the clothed body) were measured with a thermal manikin. These parameters were also measured for 39 component fabrics using a sweating hot plate apparatus. A two.dimensional computer model was developed that estimates the resistance to dry and evaporative heat transfer and the permeability index for a clothing system from fabric resistance data, fabric thickness data, and information concerning the amount of body surface area covered by different fabric layers and the amount of air trapped between fabric layers. The predictions generated by the model were compared to values measured with a manikin. The resulting standard errors were low, particularly when nonpermeable ensembles were eliminated. The data also indicated that the evaporative resistance value for common, indoor clothing could be estimated using a constant irn value of 0.38, the insulation value for the ensemble, and the Lewis Relation.