Have you run across the term “down fill power” while shopping for sleeping bags, puffer jackets, or a duvet? These numbers range from 450 to 900, and sometimes above. Generally—but not always—the ...

Forbes contributors publish independent expert analyses and insights. Terri Williams is a journalist covering housing trends. If you plan on buying a house, you often need to make a 20% down payment.

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Geese and ducks use down the same way we do: to insulate. The biggest difference is that they grow theirs, and we take ours—from the clusters of soft, fine feathers under their bellies. But how do ...

Down remains, arguably, the most efficient insulator available (although Aerogel with its amazing 95% air content, is trying), with which to make cold-weather garments, sleeping bags and bedding, ).