Cold Weather Sleeping Bags

Long Days and Longer Nights

You've been at it all day, plowing ahead through thigh deep powder and then inching your way across the boiler plate ice on a frozen ridge. As the sun sinks in the West, your thoughts drift to visions of a warm nights sleep, buried in the depths of your mummy bag. Your mini-thermometer clipped to your backpack reads 13 below zero. Good thing you spent a few extra bucks and carried a few extra ounces...

After your expedition tent, bivy bag, or snow cave, your sleeping bag is the main ingredient to a pleasurable night. With all the varieties and different options available, narrowing down your choice between a few bags can be difficult. The following breakdown of fill and shell materials, and linked tables should help you in your quest.

Down vs. Synthetic

The argument over down vs. synthetic sleeping bags has raged for as long as synthetic bags have been produced. Down is light and very compressible, while the same insulation value from a synthetic fill tends to weigh more and be less compressible. The big trade off is that down loses much of its insulation value when wet, while synthetic fills remain warm when wet. Of course, another big factor is cost. A quality down bag can easily cost double the price of a synthetic bag with the same temperature rating.

The fact that down loses its insulation value when wet generally is not as much of a problem with cold weather bags. The idea being that you usually will not run into too much water at twenty below zero. If you have a problem with your sleeping bag getting wet, then you need to evaluate your camping techniques. Line your stuff sack with a plastic trash bag, be careful with open containers of water in your tent, and simply brush out any spindrift that might blow into your tent when you enter or exit it before the snow has a chance to melt. During long expeditions in cold climates, moisture evaporating from your body can collect and freeze inside the insulation of the bag. This frozen moisture will prevent the bag from lofting properly and will reduce its insulation value. This can be avoided with the use of a Vapor Barrier Liner (VBL). Kind of like sleeping in a sandwich baggie, some people find VBL to be clammy and uncomfortable, while others enjoy the added warmth they provide. A VBL is a personal preference that has to be experimented with individually.

While the price tag on a quality down cold weather bag can cause sticker shock, buyers must be aware that a down bag will typically outlast two or maybe even three synthetic bags. Every time a sleeping bag is compressed and stuck into a backpack, the fill loses some of its loft. Down bounces back from compression much better than the best of today's synthetics.

Temperature Ratings

While there's been talk about an industry standard for sleeping bag temperature ratings, one hasn't been implemented yet, so consumers still need to rely on rating provided by the individual manufacturers. When a bag is temperature rated, one thing common among manufacturers, is that the following conditions are assumed:

  1. The sleeper had a full, warm dinner and is well hydrated.
  2. The bag is being used inside a tent.
  3. A quality sleeping pad is being used.
  4. The sleeper is generally a warm sleeper.

With all these assumptions in mind, especially the last one, better temperature ratings are given over a range rather than with a single figure. Ranges generally span about 10 degrees F, but can be as much as 15 degrees F. If the manufacturer on gives one value, then it's safe to assume that the value represents the best of all conditions.

 Shell Materials:

Diamond Lite Ripstop - The North Face's water resistant nylon shell.

DryLoft - a water resistant, windproof, and breathable shell that adds a few degrees of warmth to a bag.

Microfiber - a polyester shell designed for water resistance and breath ability.

Nylon - a soft fabric that is not very strong or water resistant.

Polyester Taffeta - a soft fabric that is a little stronger than nylon, but not much more water resistant.

Ripstop Nylon - this nylon has heavy threads running through it that for little squares in the fabric. It is strong and fairly wind resistant, however it is still not very water resistant.

Fill Materials:

Down - natural goose down provides the most insulation per ounce. Down quality is measured in Fill Power, which is determined by putting one ounce of down in a test cylinder, weighting it down with a 68.4 gram lid. The resulting volume in cubic inches is the fill power. 550 fill used to be the standard, but it has been replaced with 700 fill down. Some manufactures even claim 800 fill.

LiteLoft - a blend of polyester and olefin fibers comprised of microfine fibers heat-bonded into a fluffy lattice. Many user complaints indicate that LiteLoft quickly loses its insulation value.

Polarguard - a continuous filament polyester fill which is bulky to pack.

Polarguard HV - a newer, hollowed-out version of the original, it is light and more compressible, but doesn't last as long.

Polarguard 3D - the latest in synthetics, it's a super-fine version of the HV which has reduced weight and increased resiliency.

Primaloft - a combination of large and small polyester fibers that has good water resistance.

Quollofil - is comprised of short polyester fibers and has been found to loose its loft faster than most synthetics.