| What it is | Fluffy under-plumage of geese/ducks |
| Strength | Best warmth-for-weight; packs small |
| Weakness | Loses warmth when wet, dries slow |
| Quality rated by | Fill power |
Down insulation is the soft, fluffy plumage found beneath the exterior feathers of geese and ducks, used in jackets and sleeping bags for the best warmth-for-weight of any insulation. It lofts to trap air efficiently and packs down small, but loses most of its insulating ability when wet and dries slowly — unless treated as hydrophobic down.
Quality and choice
Down quality is rated by fill power; sources are goose or duck down. For wet weather, see hydrophobic down and down vs synthetic.
Frequently asked questions
What is down insulation?
Down is the light, fluffy clusters of plumage that grow beneath the outer feathers of waterfowl like geese and ducks. In gear, it traps air in its lofted structure to insulate extremely efficiently, giving the best warmth for its weight of any insulation and compressing very small for packing.
What are the pros and cons of down?
Pros: unmatched warmth-for-weight, excellent compressibility and packability, and long life if cared for. Cons: it collapses and loses most of its warmth when wet and dries slowly, it costs more than synthetic, and it raises animal-welfare considerations (addressed by responsible-down certification). Hydrophobic treatments reduce the wet-weather weakness.
How is down quality measured?
By fill power — the loft of the down, measured as the cubic inches one ounce fills. Higher fill power (e.g., 800–900) means loftier, more efficient down that gives more warmth for less weight. Total warmth also depends on fill weight, the actual amount of down used.
Sources
- Down vs synthetic — The Mountaineers
- Insulation basics — American Hiking Society