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Comparing Insulation - Polyester Batting or Polyester Fleece

Introduction: Polyester Batting and Polyester Fleece are two popular types of insulation for clothing and sleeping bags. Fleece is a stronger material but holds less air, so is convenient for stitching garments, whereas batting is more suitable as a filling for sleeping bags, combined with a stitched cover. We would expect that batting is a better insulator because it traps more air. Let's see.

Method: I took two flasks of boiling water ( 0.5 kg water ) and wrapped one with batting and the other with fleece. I waited one hour and measured the temperature. I repeated the experiment twice to avoid errors. Here are the results:

Batting ( Exp 1 ) Fleece ( Exp 1 ) Batting ( Exp 2 ) Fleece ( Exp 2 )
Area Density ( kg / m2 ) 0.283 0.192 0.281 0.198
Temperature Loss ( Kelvin per hour from boiling ) 20 29 21 26
Insulation Value ( Inverse of Previous Row, Proxy for R value ) 0.050 0.034 0.047 0.038
Insulation Value per Area Density 0.176 0.177 0.167 0.191

Conclusion: Temperature loss is proportional to the energy lost by the material and is inversely related to the R value of the material. According to this quick experiment, batting and fleece are almost the same. So fleece, with its other advantages, is the winner.