When it comes to staying warm in subfreezing temperatures, people tend to rely highly on technology. The human body isn't designed to stay warm without an external layer. Thermolite insulation is one invention used in clothing designed to provide lightweight warmth in cold weather.
DuPont scientists are credited with inventing Thermolite. During the invention process, they looked to nature and realized that polar bears' hollow hair keeps the animals warm. The scientists used that aspect in their work to develop a lightweight, flexible material that would keep its users warm in chilly situations. The current manufacturer of Thermolite products is Advansa.
Thermolite insulation contains hollow-core fibers with a larger surface area than other fabrics. That quality is designed to speed the process of moving moisture from skin to the fabric's exterior surface so it can evaporate at an accelerated rate. The best way to keep warm is to dress in layers of clothing. Thermolite insulation's manufacturer recommends using a Thermolite clothing item as a mid-layer when wearing such an item of clothing. Even when Thermolite is wet, it reportedly continues to keep its wearer warm and doesn't add excessive weight. The fabric also is designed to allow the wearer almost full movement.
Each grade of Thermolite insulation is designed slightly differently and for different purposes. Thermolite Extra is designed to be resilient and have a softness and fullness similar to down feathers. Thermolite Micro is made to offer compact, lightweight comfort, even when wet. Thermolite Plus is for extended wear in subfreezing conditions. Thermolite Active is made to allow for the greatest amount of movement among the product's grades. Thermolite Extreme is designed to provide as much warmth as possible, including in the coldest conditions.
Thermolite Plus, Micro and Extreme grades are used in a number of clothing items, including jackets, socks and gloves. Thermolite Active-grade fabric is used in ski wear, and Thermolite Extra is used in sleeping bags. Thermolite insulation is used in boots, too.