Finding & Buying the Right Sleeping Bag

admin May 3, 2008

A long day on the trail should be rewarded by a cosy warm sleeping bag to crawl into once the fire goes out and stargazing is done. A good sleeping bag can make a tent seem as luxurious as a four-star hotel, but the wrong sleeping bag makes for a restless night - and a harder hike the next day.

A sleeping bag’s temperature rating is a guide, not a promise, so don’t be surprised if you’re shivering in a bag rated 30F/-1C when it’s 35F/ 2C outside. Good sleep is warm sleep, so decide what the lowest temperature you’re likely to be out in is and then err on the side of caution. Women tend to sleep ‘colder’ than men, an increase in altitude corresponds with a drop in temperature, and wet weather feels colder than it really is.

A sleeping bag’s shape also impacts how warm you’ll sleep. Mummy bags are classics for a reason: the tapered design featuring a narrow foot box and wider shoulders will maximise warmth while minimising weight. A good mummy bag will include a neck yolk and a hood, since 30-50% of heat escapes from your head.

A semi-rectangular or barrel bag is good alternative if a mummy bag feels too confining because they offer a little more room for the feet without adding unnecessary bulk like rectangular bags do. Semi-rectangular or barrel bags rarely come with hoods.

Choosing between a synthetic bag and a down bag comes down to how much you want to carry, what sort of weather you’re hiking in, and what your values are.

Synthetic sleeping bags have come along way since they were first introduced. Synthetic insulation is constructed from slightly melted plastic fibres or plastic fibres sprayed with a binding resin. The fibres are hollow to reduce weight and to increase the amount of hot air the batting can trap, and are a mix of lengthy strands and ’staples’ that are less than four inches.

Synthetic sleeping bags used to be too bulky to take on multi-day treks, but the new generation of synthetics can better mimic down’s advantages and already exceed down in wet weather performance. Synthetic fibres dry quickly, don’t hold in odours, are non-allergenic, and provide a vegan option for hikers who aren’t keen on sleeping on waterfowl. The Marmot Pounder 40F features Primaloft and is only 1lb 5oz (595g), for example, and is a good choice for travelling light and fast with a synthetic.

For the ecologically minded, the Marmot EcoPro is insulated with a synthetic made from recycled pop bottles, has a minimum 30F/-1C rating, and weights 2lbs 1oz (936g).

But no matter how far synthetic bags have advanced, nothing beats a down sleeping bag for
warmth, compressibility, and wicking. Down is made of the tiny, soft, curled feathers from the chests of ducks and geese raised for meat, and its hollow shafts and the spaces between fibres make it the best existing insulating fill. Quality is determined by it’s loft (fluffiness), which is measured by the number of cubic inches an ounce of down can fill.

Down is compactible and light - the Western Mountaineering Ultralight Sleeping Bag, for example, is 850 fill power down with 5.5 inches (14cm) of loft and weighs a mere 28oz to 31.6oz (795g - 895g) depending on length.

A down sleeping bag is an investment, since down can cost twice as much as synthetic sleeping bags. Down bags last two to three times longer, though, and natural fibres in lieu of plastics mean that down is easier on the environment. Down also moulds itself around a sleeping body, which means a warmer night with fewer drafts - something even PrimaLoft can’t fully reproduce.

The downside to down is that it doesn’t dry nearly as quickly as synthetic insulation, and therefore isn’t a good choice for long trips in consistently wet weather. A down bag won’t air dry next to a fire, and it’ll be heavy if it gets damp. If night-time perspiration is an issue, bring a silk sleeping bag liner to wick the sweat away from your body and to keep it from being absorbed into your bag; silk is light to carry and easy to air dry.

A sleeping bag’s outer liner is usually either rip-stop nylon or something more weather resistant, but a little heavier. Nylon is tough, moderately weatherproof, and highly breathable, and a good all-around choice. Wet conditions might call for more waterproofing, so DryLoft and competition, such as Mountain Hardware’s Conduit, are useful, if more expensive.

Fit needs to be considered once a synthetic or down sleeping bag has been chosen. Backpackers over six feet will want a Long sleeping bag, while those under six feet will fit a Regular length. Lefties tend to prefer right zippers, and vice versa.

Most brands, such as Marmot, Mountain Hardware, and REI will carry sleeping bags cut specifically for women. A bag cut for a woman will be narrower through the shoulders, wider through the hips and footbox, and will have a roomier chest. A sleeping bag that contours the body is less likely to leak heat in the middle of the night.

Hikes in cold weather demand an overbag to add warmth and move the dew point further from the body. In warm weather, moisture passes through a sleeping bag’s insulation and evaporates, but when its cold, perspiration condenses closer to the body. The dewpoint can be so close that its actually inside a sleeping bag’s insulation. An overbag provides enough warmth for moisture to pass through the insulation before condensing, therefore keeping the bag dry.

Big Agnes manufactures a range of overbags that have slots for sleeping pads, eliminating the nocturnal ’seek & roll’ for hikers who can’t stay still. Big Agnes Cross Mountain (down) and Buffalo Park (synthetic) both add 40F to a sleeping bag’s rating, will mate with any sleeping bag of the same zipper length, and doubles as a light summer sleeping bag.

A good night’s sleep is the difference between an incredible trip and a miserable slog, so the right sleeping bag is as essential as a light stove and sturdy boots. Take the time to choose the best for you, and sleep secure in the knowledge that you’ll be fresh and energised come dawn.

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