Down Versus Feathers
High-quality down sleeping bags are not filled with normal feathers. Instead, they use the soft, fluffy insulating material that lies beneath a bird's normal plumage. This material does not have the normal rigid spine of feathers, and looks and feels more like spun silk than vanes. This allows it to "fluff" or loft.
Insulating materials trap the warmth of your body using air pockets. In fact, staying warm has more to do with trapping air next to your body than with keeping it out. This is why you should dress in layers in the winter---and why quality down is such a good insulator. The smaller the down, and the more air that it traps inside a sleeping bag, the higher its loft.
Weight and Loft
The popularity of down is largely due to its weight to loft efficiency. Every ounce of down material traps more air (and heat) than its synthetic counterparts. And the same properties that allow it to insulate so well with so little weight also allow it to be compressed. Down bags can be stuffed smaller than synthetics and still retain their loft when unpacked.
Article Written By Greg Johnson
Greg Johnson earned his Bachelor of Arts in creative writing from The Ohio University. He has been a professional writer since 2008, specializing in outdoors content and instruction. Johnson's poetry has appeared in such publications as "Sphere" and "17 1/2 Magazine."