With only a handful of exceptions, the sleeping bag is one of those pieces of gear almost every overlander needs to have in their inventory. Whether you slumber in the luxurious confines of a rooftop tent, or out in the open on bare earth, a sleeping bag is often the only thing between you and chattering teeth. Although most sleeping bags look much same, there is a tremendous difference between bags if evaluated across a wide spectrum of features, materials and other attributes. Selecting the right bag for your endeavors will not only keep you comfy on a long cold night, it can save you from making an expensive purchase twice. Finding the right bag is a simple matter of assessing a few key considerations.
A bag for all seasons
Sleeping bags generally come in three distinct categories arranged by season. There are summer bags ideally suited for temps between 30-50ºF, winter bags for extreme temperatures well below freezing, and the most common bag, the three-season bag which is designed for use in moderate temperatures ranging from 20ºF to 30ºF. When selecting your bag, be sure to buy a bag for the more extreme lower reaches of your anticipated temperature range.
Shapes and styles
Sleeping bags come in an increasing variety of shapes and styles as manufacturers compete for market share. Traditionally, this boiled down to two dominant styles: the generously cut rectangular bag and the somewhat constrictive mummy bag. Today’s selection includes a new crop of quilts, spoon-shaped bags, and genuine oddities like the Selk bag, which is really a sleeping suit.
The shape of the bag has a direct impact on its efficiency, packed size, and general comfort. A snug mummy bag is an optimal choice for those needing maximum warmth relative to the volume and weight of the bag. Those needing the lightest options available will also be best served with a mummy bag as well as those venturing into extreme cold as that shape offers the maximum warming efficiency.
Summer sleepers may prefer using one of the newer quilt systems like those offered by Nemo Equipment and Thermarest as they are lightweight, roomy, and allow for ample venting if things get a little warm mid-sleep. A quilt allows the sleeper to simply throw a leg or two outside the system, or push it off entirely just as we all do in our own beds. As a side note, quits are not typically offered in temperature ranges below 30ºF for one simple reason––they lack hoods. The only way to properly defend against freezing temps is with a fully shaped and insulated hood, which is tough to fit to a quilt.
Rectangular bags and the newer spoon-shaped offerings like those from Nemo Equipment are squarely aimed at the sleeper looking for maximum comfort without the constrictive squeeze of a mummy bag. Larger sleepers, or those prone to get a little claustrophobic will gravitate towards these systems. The penalty is obvious, the larger the bag, the larger the packed size and weight. For many people traveling in a full size vehicle, a large bag is of no consequence. For a bikepacker or even motorcycle traveler, such luxuries cannot be afforded and the mummy bag may be the only option. Like summer bags, rectangular bags, which often lack a hood, cannot easily facilitate extreme low temperatures.
This is perhaps the most critical consideration when deciding which bag is best suited to your needs. There are but two real options here: down or synthetic fibers. The traditional logic has always asserted that while down has the superior weight to warmth ratio, it is also easily stymied when wet. Synthetic fills are less effected by water and are far cheaper to produce, but don’t pack down quite as small. Synthetics also don’t breath as well sometimes making them feel stuffy, and have a shorter useful lifespan. All of this has been further complicated with the advent of what amounts to nearly waterproof down. You can read more about the pros and cons of each type of fill [HERE] in a piece dedicated specifically to this very subject.
It’s important to note that just as not all feathers are the same, the same is true for synthetics. Lesser synthetics will be heavy, bulky, and begin to lose their loft and insulating qualities quickly. Inexpensive down, which can often include duck down versus the superior goose down, can even develop a foul fowl smell. As is often the case, price and quality are often interlinked.
The temperature rating as applied to sleeping bags can be tricky business. Some manufactures don’t test their bags at all and simply slap a number on it almost arbitrarily. Some still rate the temperature by how many ounces of fill they use, which is an equally vague way to rate a bag. For many years, most bags sold in North America were tested in a cold chamber in Manhattan, Kansas giving the industry a relatively reliable standard provided every manufacture opted to use that resource. Using that system, most bags were given a singular number as the temperature rating. This number denoted the temperature at which the bag would retain the sleeper’s survivable body temp. In short, if you used your 20ºF sleeping bag in actual 20ºF temperatures, it was going to be a night to remember, one flirting with hypothermia for some.
Seeing a need for greater label clarity, most bag manufacturers have now switched to the EN 13537 standard which uses a range of temperatures to denote a bag’s warmth value. This system lists a low limit, high limit, and ideal temperature for maximum comfort. It’s important to note that any bag rating assumes the bag is being used on some form of sleeping pad. Toss your $500 exotic bag right on the ground and its temperature value is moot as that cold ground conducts its chill right to your bones.
Features and construction
There are certain features that are little more than thoughtful refinements which make the bag more enjoyable to use. Things like glow-in-the dark zipper pulls, or well placed pockets for your headlamp are nice touches, but other features are performance based. A good cold weather bag should have a baffle around the neck and along the zipper to seal in warm air and shut out drafts. I’m growing fond of some of the newer features like pad-keeper straps like those used on the Thermarest Antares sleeping bag.
How a bag is constructed is oft overlooked yet one of the most important aspects within the selection process. This is largely relative to how the insulation baffles are shaped and constructed. A good bag avoids any stitched seams that pass through to the interior of the bag. Such seams allow cold air to pass directly into the bag. This is less of a concern for summer bags. The baffle structure also needs to prevent the fill from shifting or tearing, thus creating cold spots. Well designed baffles also don’t collapse with every movement of the sleeper. Pushing against the inside of the bag should not compress the baffle, again something that would create a cold spot. It’s quite impressive how much detail goes into baffle design. Many bags come with trapezoidal shaped foot-boxes to best match the shape of a sleeper’s feet. A good hood when pulled close to the head, will not create any deep folds that could displace insulation and invite the ingress of cold air. There’s much to evaluate with regard to how a bag is constructed and these elements factor heavily into a bag’s asking price.
Although a good bag is worth far more than the sum of its parts, the parts are nonetheless very important. Shell fabrics can play a major role in the valuation and performance of a bag. A sub one-pound bag often achieves that low weight by virtue of exotic materials like 15 denier ripstop nylon that has the weight of tissue paper but with surprising durability. Conversely, an inexpensive bag may employ basic fabrics prone to degrade, or even suffer from mildew or worse. With regard to fill materials, the quality variables for both down and synthetic fills have a dramatic impact on a bag’s price and performance. Even something as simple as zipper quality can translate to a comfortable night, or one of complete misery.
The value proposition with regard to sleeping bags is one maligned with false truths. Many consumers often see a $100 synthetic bag as a better value than a $250 down bag. In some cases this may in fact be true, but not always. A high quality down bag made of good materials and well cared for, can often outlive a synthetic bag by at least a factor of two. The newer water-resistant down bags promise to up that number by at least a factor of three or more. This means a high quality bag filled with water-resistant down might hold its temperature value for 10, 15, maybe even 20 years. Many synthetic bags start to show a decline in temperature value after as little as 3 to 5 years. These are difficult numbers to pin down as care and maintenance factor heavily into sleeping bag longevity, but there is no doubt some bags simply outlive others and the initial purchase price is often an indicator of that longevity.
In the end, arming yourself with as much product research as possible is the best way to select a sleeping bag. Be honest with your individual needs and know that unlike more expendable pieces of gear, a good sleeping bag, given proper care, can endure years of loyal use.