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Clothing insulation is the thermal insulation provided by clothing.〔ANSI/ASHRAE Standard 55-2010, Thermal Environmental Conditions for Human Occupancy〕〔Schiavon S., Lee K. H. (2012), Dynamic predictive clothing insulation models based on outdoor air and indoor operative temperatures, Building and Environment (http://dx.doi.org/10.1016/j.buildenv.2012.08.024)〕 Even if the main role of clothing is to protect from the cold, protective clothing also exists to protect from heat, such as for metallurgical workers or firemen. As regards thermal comfort, only the first case is considered. == Mechanisms of insulation == There are three kinds of heat transfer: conduction (exchange of heat through contact), convection (movement of air), and radiation. Air has a low thermal conductivity but is very mobile. There are thus two elements that are important in protecting from the cold: * stopping the wind from penetrating and replacing the layer of warm air close to the body; * setting up a layer of still air which serves as insulation, by the use of fibres (wool, fur, et cetera). Another important factor is humidity. Water is a good conductor of heat, thus if clothes are damp — because of sweat, rain, or immersion — water replaces some or all of the air between the fibres of the clothing, causing heat loss through conduction and/or evaporation. Thermal insulation is thus optimal with three layers of clothing: * a layer near the body for hygiene (changed more often than the other clothing), whose role is to get rid of sweat so it does not remain in contact with the skin; * an outer close-knit or closely woven layer as a wind breaker, usually thin — if there is a risk of bad weather this should be impermeable, the ideal being a textile that stops water droplets but allows water vapor to pass so as to remove evaporated sweat (a textile of this sort is said to "breathe"); * and between the two, a "thick" layer that traps the air and prevents contact between the skin and the wind-breaking layer (which, as it is thin, gets close to the ambient temperature). The three layers of air between the skin and the exterior layer also play an insulating role. If the clothing is squeezed tight (as by the straps of a backpack), insulation will be poorer in those places. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Clothing insulation」の詳細全文を読む スポンサード リンク
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