Fabric Properties And Comfort

Step 1: Understand thermal insulation. The primary purpose of insulating clothing is to prevent heat loss from the body. Heat is primarily lost through convection and conduction. The most effective way to prevent this is by trapping a layer of still air. Still air is a very poor conductor of heat.

Step 2: Analyze how fabric properties relate to trapping air. A fabric's ability to trap still air is directly related to its structure. A bulky, porous fabric will trap a lot of air. The most direct measure of this capacity to entrap air is the fabric's thickness. A thicker fabric inherently traps a thicker layer of still air, providing greater insulation.

Step 3: Evaluate the other options.
- (B) Stiffness and (C) Crease recovery are mechanical properties that do not directly determine insulation.
- (D) Weight can be misleading. A very heavy but thin and dense fabric (like a thin sheet of metal) would have poor insulation. A very lightweight but thick and lofty fabric (like a down jacket) has excellent insulation.

Conclusion: The most important factor determining the thermal insulation of a fabric is the amount of still air it can trap, which is best represented by its thickness.