Air Gap Insulation and Geometric Effects
topic
Air gaps between clothing layers and between garment and body surface contribute substantially to thermal protection through still air insulation at thermal conductivity of 0.025 watts per metre Kelvin, with a 6 millimetre air gap providing thermal resistance equivalent to several millimetres of typical woven fabric, diminishing under compression and body movement that collapses air spaces, making air gap preservation during realistic movement an important design objective for garment construction.
Role
Contributes significant thermal protection without adding material weight, with air gap insulation value guiding garment construction toward designs that maintain adequate air space during movement and supporting the use of thermal manikin testing that includes realistic air gap geometry in contrast to flat specimen testing that underestimates total system protection by excluding the air gap contribution to thermal resistance.