DeWoolfson Frequently Asked Questions
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What determines a comforter's warmth? What is fill power?

Your question is more complicated than you might have thought - so here goes. Down is the most insulating of all materials because of its unique ability to loft and trap body heat within the air space it creates. The greater the loft, the warmer the comforter. The wonderful characteristic of down is that very little of it (by weight) will loft and fill a great volume. A comforter can be made warmer in two ways: By increasing the quantity of down (in ounces); or by using a higher quality down with greater loft. The ability of down to loft, or to fill a given volume of space, is called fill power. Fill power is measured in cubic inches of volume. One ounce of 650 fill power down, will loft to fill a volume of 650 cubic inches. Fill power ranges from about 500 to 800 for special types of white goose down. Thus, in order to achieve maximum "warmth without weight", we recommend at least a 650 fill power down. Our hand selected 750 fill white goose down has approximately 15 percent more warmth than our 650 fill power down. Feathers have little insulating ability because they do not have the same lofting characteristics of down.

Be careful in selecting a very warm comforter. Our experience is that many people are truly surprised at how much heat a comforter retains. We can add down to most comforters at any time after purchase, charging only for additional down added. But we cannot remove it from a comforter that is too warm. So if you are unsure, consider selecting a comforter that is one step lighter than you thought you would need.

DeWoolfson uses only all European fill.

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