Which fabric insulates when wet?

• A. Wool
• B. Cotton
• C. Silk
• D. Nylon

Answer: (A)

Insulation depends on trapped air to slow heat loss. When a fabric gets wet, water can fill the air gaps and carry heat more readily, making the material feel colder. The fabric that stays warmer when wet has a structure that keeps air pockets and loft even after soaking. Wool fits this well because its crimped, fibrous structure creates many tiny air spaces and it can absorb moisture without collapsing its loft. That combination lets wool hold onto insulating air and keep you warmer even when damp.

Cotton, by contrast, soaks up water and the fibers tend to clump, reducing those air pockets and cutting insulation when wet. Silk and nylon don’t maintain loft and insulating air as well once they’re wet, so they lose warmth more quickly in damp conditions.