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To provide insulation from cold: Warmth of clothing and sleeping bags is directlyproportional to thickness and independent of weight.Warmth results from small bodies of dead air enclosedby cell walls or held between numerous fibers. For thisreason several layers of fluffy, loose-woven sweaters arebetter than hard-woven garments weighing several timesas much. Down, feathers, and wool, in the order named, arethe best insulators. This is true for both sleeping bagsand clothes. Sleeping bags should be covered with tightly wovencloth to prevent warm-air permeation as well as to contain the down. A complete hood extending over the headprevents loss of warm air around the shoulders and insulates the neck and head. Heat loss from an unprotectedhead and neck exceeds that from the remainder of thebody when protected by a sleeping bag. Form-fitting design with the outer shell cut larger than the inner shellgives most insulation for least weight. |
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