What is your most important piece of equipment for comfort? We're talking about in winter with those beautiful sunny days when a windshell and underwear seem to be all you need. Those beautiful, sunny SHORT days. So how do you enjoy the other sixteen mind-numbingly cold hours of darkness around the tent? Shivering? Huddled into a tight ball with the smallest possible exposed surface area? It takes little effort to be uncomfortable; but a little extra can make you look forward to those long nights snug in a cocoon, a home away from home bed, without having to cart along every bit of insulative clothing you own.

As with clothing, a sleeping system adjustable to any conditions often makes the best sense, as well as avoiding the purchase of a range of sleeping bags to select from throughout the year.

The Sleeping Bag

Something in the minus 10 range is a good starting point-you might need that coziness on a clear summer night in the mountains. Then the most difficult decision: Synthetic fill or Down? Synthetics are the least expensive and might seem the logical choice, but remember that the fills (they are all just polyester fibre mats teased and fluffed and stabilized somehow to create loft) will gradually collapse with use and trap less warmth. Even the most stable of fills, like Polarguard, will lose 25-30% of its loft in a year of regular use. The new softer, lighter and more compressible Lite Loft is not exempt. So don't expect more than a couple of years of performance from a synthetic. Down, of course, is more expensive, and the price of a bag filled with a highly refined down of 650 or 700 fill power can seem astronomical. (The higher the fill power number, the more insulation from a given weight of down-anything under 500 cubic inches per ounce will be as heavy as a synthetic fill bag.) But, cared for properly, a down bag can last a lifetime, so the initial investment will save you money in the long run. Whatever you buy, store it fully fluffed. The more any insulation is compressed, the less it will bounce back to its air-trapping state.

More Than Stuffing

The performance of a bag is more than just its stuffing: tight, mummy-shaped bags have less dead space to be warmed by your body than roomy bags; a yoke built into the neck stops warm air billowing out of the bag as you breathe and move; a well-fitting hood keeps your head and the rest of your body warm. A windproof shell reduces convective heat loss from the insulation and can significantly improve the efficiency of the bag with little increase in bulk or weight. Gore-Tex shells used to be a popular extra for this reason, but the waterproofness of the fabric could lead to the build up of condensed (and, in cold weather, frozen) perspiration in the insulation, so Gore no longer licenses the use of Gore-Tex in sleeping bags. Gore's new product, DryLoft, is a lot more breathable and reduces the condensation problem, although it can't completely prevent the physical process of water vapour condensing at the dew-point somewhere between a 37 degree body and the minus 20 air on the outside of your sleeping bag. If your bag can't be dried out during the day, accumulating moisture in the insulation can be serious on a multi-day trip. Hence the addition of another layer to your sleeping system.

Stop the Moisture

A vapour barrier liner (VBL) inside your sleeping bag stops perspiration from reaching the insulation. Skin produces moisture constantly to maintain its humidity around 80%. This means constant heat loss from your body as the moisture evaporates, as well as the condensation problem. A VBL traps the moist air around your body, reduces sweating, and adds 5-10 degrees of insulating power to your sleeping bag. Contrary to expectation, a VBL is not a horrible, sweaty, steam-bath, as long as it is cold enough outside, and it is an easy and light way to extend the temperature range of your sleeping bag.

If you are still cold, add a thin overbag. This can add 10 degrees to your bag through a combination of reduced convective heat loss and plain extra loft. An overbag also keeps your main insulation drier by moving the dew-point to the external layers.

Finally, and very importantly, don't skimp on an inadequate sleeping pad. It makes no sense to trap all your heat above your body if it is being sucked out from below.

For more information

Contact Mountain Equipment Co-op in Calgary at (403) 269-2420

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