There are many methods of measurement to analyse the specifications of fabrics like heat transfer and water vapour permeability. However, in practice, the air layers between the different fabrics fundamentally influence the wear comfort. With the sweating arm developed at EMPA, it is now possible to simulate the heat and moisture transfer under realistic conditions. The goal of this study is to analyse the interactions between the different parameters which influence the thermal and water vapour resistance. These parameters are basically the temperature, the degree of humidity, different widths of the sleeves, the pumping effect of the movable forearm and the wind velocity.
The study shows that the thermal insulation of the air layers is 5 to 50 times higher than the material itself. Wide sleeves have in average a 30% higher thermal insulation than narrow sleeves.
It could be prooved that thermal and moisture transfer do not correlate with each other: for one sample, even if the wide sleeve has a much higher thermal insulation than the narrow one, the water vapour resistance is much lower.