Which natural fiber material best maintains its insulative properties when wet?

Wool is the natural fiber that best maintains its insulative properties when wet. This is due to the unique structure of wool fibers, which contain tiny air pockets that help trap heat. Even when wet, wool fibers can still provide thermal insulation because they continue to trap air, which is a poor conductor of heat. This characteristic allows wool to keep the wearer warm in colder, wet conditions, making it a favored choice for outdoor clothing and gear in environments where moisture is a concern.

In contrast, cotton loses most of its insulating capabilities when it becomes wet. Unlike wool, cotton fibers absorb water, causing the material to become heavy and cool to the touch, which can lead to heat loss and increase the risk of hypothermia in cold, wet conditions.

Acrylic and nylon, while synthetic and offering specific advantages—like being lightweight and quick-drying—do not have the same insulative properties as wool. Acrylic offers a softer feel and can mimic the warmth of wool, but it does not insulate well when wet. Nylon is primarily known for its durability and water-resistant properties, but it does not provide significant insulation in wet conditions, as it lacks the natural insulating properties found in wool.