Change of footwear insulation at various sweating rates

Moisture inside the footwear can considerably affect the thermal insulation. In this study with a thermal foot model there was simulated three sweat rates (3, 5 and 10 g/h). Five types of footwear with various insulation levels (dry insulation from 0.19 to 0.50 m2•K/W) were tested. The footwear insulation reduction was calculated for 1.5 hour period. The reduction in insulation was related to sweating rate and initial insulation. The footwear with high insulation lost even in percentile more insulation than thin boots at the same conditions (9-19 % at 3 g/h, 13-27 % at 5 g/h and 19-36 % at 10 g/h). A relationship between insulation decrease and sweating rate was established. An 8-hour sweating test (5 g/h) and a test for determining evaporative heat losses were carried out in addition. The insulation reduction during the first 1.5 hours of the 8-hour test answered for more than half of the total reduction.