The Effect of Changing Humidity on the Insulation of Hygroscopic Clothing

Abstract

Two series of experiments are described in which the insulation walue of wool fabrics is measured during the process of sorption or desorption by the fabric. The results are discussed from the point of view of the buffering action of clothing made from hygroscopic fibers. The buffering effect predicted in 1941 by Cassie et al. has been detected in a physical, as distinct from physiological, experiment, but only 30% to 50% of the total sorption heat is effective in reducing heat loss through the fabric. These measurements, combined with some measurements of regain changes of a wool suit on a wearer, suggest that, immediately after a change in atmospheric RH from 50% to 80%, the heat loss from a subject wearing such a suit is reduced by about 12% of the resting human metabolic rate and that this buffering effect is reduced to about 3% of the metabolic rate after 20 min. The prediction based on the assumptions that the regain change would be in accordance with the standard isotherm and that all the sorption heat would be available to the wearer is, therefore, an optimistic one.