Clothing insulation and temperature, layer and mass of clothing under comfortable environmental conditions

This study was designed to investigate the relationship between the microclimate temperature and clothing insulation (I(cl)) under comfortable environmental conditions. In total, 20 subjects (13 women, 7 men) took part in this study. Four environmental temperatures were chosen: 14°C (to represent March/April), 25°C (May/June), 29°C (July/August), and 23°C (September/October). Wind speed (0.14ms(-1)) and humidity (45%) were held constant. Clothing microclimate temperatures were measured at the chest (T(chest)) and on the interscapular region (T(scapular)). Clothing temperature of the innermost layer (T(innermost)) was measured on this layer 30 mm above the centre of the left breast. Subjects were free to choose the clothing that offered them thermal comfort under each environmental condition. We found the following results. 1) All clothing factors except the number of lower clothing layers (L(lower)), showed differences between the different environmental conditions (P<0.05). The ranges of T(chest) were 31.6 to 33.5°C and 32.2 to 33.4°C in T(scapular). The range of T(innermost) was 28.6 to 32.0°C. The range of the upper clothing layers (L(upper)) and total clothing mass (M(total)) was 1.1 to 3.2 layers and 473 to 1659 g respectively. The range of I(cl) was 0.78 to 2.10 clo. 2) Post hoc analyses showed that analysis of T(innermost) produced the same results as for that of I(cl). Likewise, the analysis of L(upper) produced the same result as the analysis of the number of total layers (L(total)) within an outfit. 3) Air temperature (t(a)) had positive relationships with T(chest) and T(scapular) and with T(innermost) but had inverse correlations with I(cl), M(total), L(upper) and L(total). T(chest), T(scapular), and T(innermost) increased as t(a) rose. 4) I(cl) had inverse relationships with T(chest) and T(innermost), but positive relationships with M(total), L(upper) and L(total). I(cl) could be estimated by M(total), L(upper), and T(scapular) using a multivariate linear regression model. 5) L(upper) had positive relationships with I(cl) and M(total), but L(lower) did not. Subjects hardly changed L(lower) under environmental comfort conditions between March and October. This indicates that each of the T(chest), M(total), and L(upper) was a factor in predicting I(cl). T(innermost) might also be a more influential factor than the clothing microclimate temperature.