Knowra Down jacket Down jacket A jacket insulated with the soft underfeathers of birds, usually ducks or geese. Its loft traps still air, slowing heat loss while keeping the garment lightweight.
Down feather : A soft bird feather with a central tuft and no stiff shaft, found beneath the outer feathers. These clusters form the jacket’s insulating fill by holding pockets of still air.
Down cluster : A three-dimensional tuft of fine, soft filaments that grows beneath a bird’s outer feathers. Clusters, rather than ordinary feathers, create most of down’s insulating loft.
Mountaineering clothing : Clothing designed to protect climbers from cold, wind, precipitation, and abrasion in mountain environments. Down jackets provide low-weight insulation in mountaineering systems, especially in dry cold.
Wool insulation : Thermal insulation made from wool fibers, which can retain warmth while absorbing moisture. Wool is a natural alternative whose performance in damp conditions differs from down’s.
Fill power : A measure of how much space a given weight of down occupies under standardized conditions. It indicates how much loft—and potential warmth for a given weight—the fill can provide.
Water-resistant down : Down treated with a durable water-repellent finish to slow moisture absorption. The treatment helps preserve loft when the fill encounters damp conditions.
Layering system : A clothing strategy that combines layers to manage insulation, moisture, and weather protection. A down jacket commonly serves as an insulating layer beneath or over shell clothing.
Fleece jacket : A jacket made from a napped synthetic textile, commonly polyester, that provides lightweight insulation. Fleece is often used as a breathable insulating layer instead of down.
Thermal insulation : The reduction of heat transfer between objects or regions at different temperatures. A jacket’s loft insulates by limiting heat transfer from the body to colder surroundings.
Shell fabric : The outer textile layer of a garment, exposed to the surrounding environment. Its wind resistance, durability, and water repellency shape how the insulation performs.
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