The thermal insulation of clothes is proportional to the trapped dead air mass. Dead air means trapping small air units as natural currents do not happen. Such flows are seen in units with diameters of 2 millimeters. Dead air near the floor is heated by the body and forms a heat strand around the body. Not the clothes that keep you warm but dead air. The longer the material is, the faster it travels through heat transmission, and the smaller the density of air compared to a piece of fabric, of course. A “clo” unit has been developed to measure the efficiency of insulation. A clo approximately corresponds to the insulation value of a normal wool suit. Each inch thickness of traditional insulation materials (wool, floors, bottoms) provides 4.7 clo theoretically and 4.0 clo insulation in practice.
The answer to the question of how to dress in winter is actually hidden in the Layering Principle. This dead air space is achieved by a number of clothing layers. Each layer provides a certain dead air value clo. This allows you to add and subtract layers to increase or decrease the accumulated dead space as the temperature changes and / or as your activity levels change. Remember, your body is a source of heat, the layers of clothing are only used to trap heat and slow down heat loss in cold environments. If you wear too many clothes, you start overheating and sweating. You need to find the appropriate heat balance between the various types of layers and the level of activity.
If you sweat, you will lose heat much faster because the water evaporates. At the same time, because the air is too dry, you will lose water swiftly and incredibly. Too much water loss leads to dehydration, which significantly increases the risk of hypothermia. For this reason, you should stay warm at the level of activity, but you need to control your layers to avoid overage. Thus, winter travel involves continuously adjusting your layers to ensure your comfort. This is to have the number of layers (clothes) you can add and remove and to allow variation among the layers (clothes).