Synthetic vs. Down Sleeping Bags

Down Fills versus Synthetic Fills

The warmth and insulating properties of any sleeping bag are related to what material, and how much, it is filled with. You will have two basic choices of fill: synthetics or down.

Down Sleeping Bags

Down sleeping bag models will be more expensive than synthetics, but last longer and are warmer. As any duck or goose could tell you, feathers are a terrific insulator. Add to this down's warmth-to-weight ratio and you have a winning combination. Backpackers and cyclists will especially appreciate the weight factor of down-filled sleeping bags.

Down sleeping bags are rated according to their fill power: 650 cubic inches per ounce means that one ounce will fill 650 cubic inches of space. A rating of 500 to 550 is pretty standard; a 750 to 850 fill rating is considered excellent. As fill power increases, so does price. When considering a particular down sleeping bag, evaluate it carefully according to the season you'll be outdoors.

Down sleeping bags are filled with one of two kinds of down: goose or duck. Downs of equal fill power perform equally well, and there is nothing inherent in goose down to make it better than duck down. But the best goose down has a higher fill power than the best duck down, which tops out at about 550 cubic inches per ounce. Check the fiber content labels on the down sleeping bags to make sure you're purchasing the right down fill.

Synthetic Sleeping Bags

Synthetic-filled sleeping bags are a cheaper alternative to the down-filled sleeping bag varieties. They appear on the market in an ever-expanding variety, but essentially all are packed with some kind of proprietary fibers (whether chopped or continuous filament).

Synthetic sleeping bags are not as warm for their weight as down-filled sleeping bag equivalents, and they don't last as long. On the upside, they are less expensive and are more resistant to wetness. When wet, they also retain some insulating value; sodden down-filled sleeping bags do not. Down sleeping bags also hang on to moisture longer, which can add extra weight—and may contribute to night-time discomfort if the sleeping bag hasn't had a chance to dry.

All sleeping bags are rated according to seasonal temperatures:

• 40° = Warm weather (Summer) (1 1/2 pounds)
• 20° = Three season (Spring, summer, and fall) (3 to 4 pounds)
• 0° = Cold weather (Early spring and late fall) (3 to 4 pounds)
• -15° = Cold weather (Winter) (6 pounds)

This guide is only representative because some people adapt to temperatures differently than others. Sleeping bags are rated for the average male, sleeping in a tent on a sleeping mat. As a generalization, women tend to sleep colder. Most people find sleeping bags rated for 20°F quite satisfactory for most conditions. If you're the type of person that gets colder than others at night and needs more covers, then go one step up in a sleeping bag's insulating capability.