What the Heck is Down Fill Power?

Posted by BAP Store on Dec 11, 2019

It may technically still be fall until December 21, but here in Steamboat the warm days, cool nights, and brightly colored leaves of autumn have long since vanished. Snow and temperatures are falling and winter coat season is fully upon us. If you have ever gone shopping for winter gear and apparel during this time of year, you have likely encountered items bearing tags that denote their level of down fill power. If you are anything like me, you have wondered what on Earth down fill power means. Fortunately my colleagues at BAP! have enlightened me with their gear expertise, so I can share with you just what exactly those numbers mean and how you can use this knowledge to stay toasty all season.

Down Fill Power Measures the Relative Lofting Quality of Down

Down is a desirable insulator in large part due to its warmth to weight ratio and its packability. Down feathers trap body heat most efficiently when they are lofted- meaning puffed out to the max. More loft creates more pockets of air, which create more space to trap heat, which results in greater warmth. The higher quality the down feathers, the fewer of them you will need to achieve a certain amount of loft.

Down fill power measures how many inches of loft one ounce of feathers can achieve. When one ounce of feathers has greater loft, it is considered to have a higher fill power. Say you are comparing two 15 degree sleeping bags and one contains 650 fill power down while the other contains 800 fill power down. The 650 fill power down bag will require more feathers to achieve the same temperature rating as the 800 fill power down bag. Thus, the 800 fill power down sleeping bag will be lighter in weight and capable of compressing down to a smaller size than the sleeping bag with the lower fill power rating.

Down Fill Power is Not a Warmth Measurement

It is important to remember that down fill power measures warmth to weight ratio, but it is not a temperature rating. Here at BAP!, we sell a plethora of cold weather layers that utilize 700 fill power down, but that certainly does not mean that all of the garments we sell are equally warm. For instance, the men's Chilton down sweater is a great layer to have while out skiing or being similarly active, but it will probably not do the trick in cold weather situations where you are not generating much body heat. Meanwhile, the men's Fire Tower belay parka is a perfect option to stay toasty while you stand around watching the kids compete with the Winter Sports Club, but should you wear it out snowshoeing? Not unless you're trying to sweat out every ounce of moisture in your body. Both these jackets contain 700 fill power down feathers, but their warmth and intended uses are very different.

Why Does it Matter?

Down fill power matters when you are looking for gear that is as light weight and compressible as possible. High fill power down sleeping bags and jackets will give you maximum warmth for minimal weight and will compress down to a small size to fit easily in a pack. However, high quality, high efficiency down does come at a price. Lower fill power down offers a more budget friendly option that still gives the benefits of down's packability and light weight, just to a slightly lesser degree. Your need for weight and space efficiency along with how much you are willing to spend are the factors most likely to determine whether you are in the market for a product with high fill power down.

Have questions about how to stay warm during your winter adventures? Come in and talk to the gear experts at BAP!

What the Heck is Down Fill Power?

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