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

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 <0-15, 0-7 and 41 m/s. Sitting increased vapour resistance by 12-36%, whereas walking and wind decreased the resistance by 72% and 89% when compared to standing with less than 0-15 m/s wind. Movement and wind interacted so that the higher the walking speed, the less additional effect of wind was observed.

Values of the permeability index I_m were calculated. Wind and movement increased I_m up to a factor three for the permeable and up to a factor six for the impermeable garments. However, using a different definition of I_m(I'_m.), based on the convective part of the heat transfer coefficient only, resulted in higher I'_m values (compared to i_m) which remained constant with wind and movement. It was shown that with increasing wind and movement I_m will increase and approach the value of

Keywords:

• Vapour permeability
• Clothing ventilation
• Microclimate
• Convection
• Diffusion