Heat Management

Passive outdoor activities in cold weather require the use of clothing to conserve heat. Clothing which is intended to reduce the rate of heat loss must be a poor conductor of heat. Textile fibres are good conductors of heat compared with still air (N.B. water is 27 times more conductive than air so fabrics must be kept dry!). All fabrics contain still air trapped between the fibres, and this air is a very poor conductor of heat. The greater the volume of trapped air, the higher the insulation value. Fabrics may be designed with a thick or a cellular structure to improve insulation and the insulation can be improved by brushing or raising the surface of the fabric. It is essential that the fabrics retain their thickness in use, and therefore, fabrics which are resilient are most desirable. If fillings or waddings are used to provide insulation, it is essential that some form of stabilisation is used to give a uniform layer. In cold weather a substantial proportion (40%) of the total heat loss may occur from an uncovered head and hands, so it is advisable to wear a hat and gloves.