When sporting your footwear in climatic conditions with very low temperatures, such as in mountaineering, glacier expeditions and ice climbing, a particular attention must be paid to the type of boot to choose, because in addition to the technical and functional characteristics, the footwear must offer an excellent degree of thermal insulation, developed in two different directions: insulation of the sole block and of the upper.
The sole package is perhaps what needs most an excellent thermal insulation. In fact, it is almost constantly immersed or in contact with the ground, covered with cold matter (snow, ice), and becomes the vehicle to transport the low temperatures inside the shoe, heading to the foot. This can be limited by using layers of specific technical material that, added to the traditional construction of the sole, considerably increase its resistance to cold, and in fact allow the sole of the foot to stay warmer, for a longer time. An example of these technologies is the use of an aluminum foil which, being thermal reflective, acts as a real shield against the penetration of the cold towards the foot.
The other part of fundamental importance that must be isolated from the external environment is the upper. Here we have the same situation, the cold and the materials that come into contact with it try to penetrate inwards. In this case, the most used technical solution is coupling the upper with a layer of insulating material developed specifically for footwear, such as Thinsulate®, which combined with the waterproof membrane is a barrier against the infiltration of water and cold to the foot. In some cases, you can also find linings directly in contact with the foot that, for construction and type, are able to perform the same function as the insulating material: for example, the synthetic wool lining, which keeps the foot warm, gives a feeling of greater comfort and guarantees prolonged use over time without losing its properties.