Layering of fabrics in laboratory tests to reflect combinations as outdoor apparel

The objective was to examine the effects of layering fabrics on selected properties known to be critical in the outdoor recreational activity market (permeability to air and to water vapor, and thermal-related measures including 'dry' and 'wet' thermal resistance). With laboratory-based testing used by manufacturers to aid fabric selection, information on the way in which fabrics behave as layered arrangements is pertinent. Comparisons of effects on fabric properties were based on fibers (merino wool, polyester), knit structures (single jersey, interlock, eyelet), and whether differences were apparent with multiple-layer arrangements typical of end use, including outer layers. Standard methods and modifications to these were applied. Some properties differed according to the spacing (distance) between layers and/or between a first layer and a hypothetical 'skin' surface. Differences among the different fabrics/fibers were more apparent with one layer than with multiple layers. Layering of fabrics which are likely to be used as garments worn together has major effects on properties such as permeability to air and water vapor, thermal resistance, and nominal thermal conductance. Effects of adding a second layer typically exceeded those of adding a third.