Clothing ventilation, vapour resistance and permeability index: changes due to posture, movement and wind

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Abstract
Using the trace gas diffusion method, the vapour resistance of three clothing ensembles (two permeable and one impermeable) was determined for four subjects, sitting, standing or walking at 0-3 and 09 m/s, combined with three wind speeds of m were calculated. Wind and movement increased Im up to a factor three for the permeable and up to a factor six for the impermeable garments. However, using a different definition of Im(I'm.), based on the convective part of the heat transfer coefficient only, resulted in higher I'm values (compared to im) which remained constant with wind and movement. It was shown that with increasing wind and movement Im will increase and approach the value of