Effects of Layering on Thermal Insulation and Vapor Permeability
Technical Report,01 Jan 2018,01 Nov 2019
Biophysics and Biomedical Modeling Division, U.S. Army Research Institute of Environmental Medicine Natick United States
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Introduction Thermal insulation of clothing depends largely on the air trapped between the skin and the clothing layers. Textile from clothing layers and the air between layers provide insulation. The purpose of this work is to examine the effects of layers and air gaps on thermal insulation and vapor permeability. Methods Standard tests for the thermal and evaporative resistances Rct and Ret were conducted ASTM F1291-16 and ASTM F2370-16 for eight military ensembles within climate controlled environmental chambers. Each of the eight ensembles varied in the types of material and number of layers 2 - 5 layers while one included a 6th layer in the form of ballistic armor. Results Thermal insulation clo ranged from 1.30 2.71 1.87 0.57, vapor permeability im 0.32 0.55 0.41 0.08, and evaporative potential imclo ranged from 0.14 0.40 0.24 0.09. Conclusion This work provides some quantitative evidence that the thermal insulation is highly dependent on the addition of air layers within clothing ensembles.
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