How to Choose a Sleeping Bag

How to Choose a Sleeping Bag

Down or synthetic? What temperature rating? Mummy or rectangular? Extra-long or women-specific?

With the range of sleeping bag types and options on the market there’s sure to be a bag (or bags) ideal for your personal thermostat, shape, and overnight destination. But with the hundreds of models to choose from, how do you find that perfect night’s rest? Read on.

What Type of Insulation?

It’s the classic sleeping bag question—down or synthetic? Which insulation you choose depends on what weather conditions you expect (heading into monsoon season? consider synthetic), how space and weight conscious you are (down packs smaller and is lighter), and your own personal preferences. Below are some pros and cons for both fills.

  • Goose down is the standard for sleeping bag fill. It compresses the best, is the lightest in weight, and is the most efficient insulator, which means it’s the warmest for its weight. It also lofts back up quickly when shaken out and lasts longer than synthetic fill when cared for properly. However, down loses its insulating properties when wet, rendering a wet bag useless, and it takes a long time to dry.

    Read Gear Explained: Down Insulation

  • Synthetic’s advantage is that it doesn’t lose its insulating properties when wet, and it dries quickly. So synthetic fiber is a good choice for very wet climates or paddling trips. Synthetic bags are usually cheaper than down ones, which can make them good values, and they are the obvious choice for anyone who’s allergic to down. While the best synthetic fills come close to down’s superior properties, synthetic bags still tend to be larger and heavier.

    Read Gear Explained: Synthetic Insulation

What Shape and Size?

Most brands make sleeping bags in several different shapes and lengths to accommodate the range of body types and sleepers out there.

  • Mummy bags, with their narrow fit, are the warmest since there is less space for your body to heat up. Mummy bags also have insulated hoods that you can snug around your head to conserve heat. Because of their slim cut they weigh the least, pack up smallest, and are the best choice for backpackers, climbers, and mountaineers. Very active and/or claustrophobic sleepers may feel confined by a mummy bag’s tighter fit.

    Some mummy bags are designed to flex or stretch with your movements to reduce that feeling of constriction (such as Sierra Designs’ Diamond Spring Flex +30 and MontBell’s U.L. Super Stretch Down Hugger #4). Other examples of mummy bags include The North Face’s Solar Flare -20° and Superlight 0°, Marmot’s Pinnacle 15°, and Western Mountaineering’s HighLite 35°.

  • Rectangular bags are the roomiest, weigh the most, and are best suited for warm weather since they don’t conserve heat as well as mummies. They are generally considered too heavy and bulky for backpacking, but can be a good choice for warm-weather car camping trips and other outings where weight and warmth aren’t a concern. Some cold and very cold weather rectangular sleeping bags are available. Examples of rectangular bags include The North Face's Dolomite 20° and Slumberjack's Talon +40°F.

  • A few manufacturers offer semi-rectangular or tapered bags, which provide a compromise between the roominess of a rectangular bag and the warmth of a mummy bag. Examples of semi-rectangular bags include Western Mountaineering’s MityLite 40° and Big Agnes's Elk Park -20°, Encampment 15°, and Lost Dog 50° .

  • Women-specific bags are designed to best fit the shape of women. This means bags that are shorter in length, wider at the hips, and narrower at the shoulders. Women-specific bags also may have more insulation in the toe box and torso areas, since women tend to be colder sleepers and lose more heat in these areas.

    Sierra Designs was the first company to develop women-specific sleeping bags back in 1995 and now offers a full line of bags for women. Other companies have since followed their lead, including Mountain Hardwear, Marmot, REI, Kelty, The North Face, and EMS.

  • Youth or junior bags for young campers and backpackers are available from several companies. After all, kids who go camping, backpacking, and on other overnight outdoor adventures need sleeping bags of the same quality as Mom and Dad’s. Sleeping bags designed for kids are smaller, of course, which makes the bags lighter and warmer. Some are expandable to grow with your child.

    Examples of kids’ sleeping bags include Mountain Hardwear's Mountain Goat 20° and Mountain Goat 40°, Sierra Designs’ Big Dog 20°, The North Face’s Tigger 20°, Marmot’s Trestles Junior 30, and Kelty's Little Dipper 20° Junior.

  • Many sleeping bags come in both regular and long lengths. Extra-long bags are designed for tall individuals (usually considered those over 6 feet, but individual manufacturers provide dimensions and suggested heights). They’re also good for anyone who needs extra space, such as winter campers and mountaineers who need to keep water bottles, batteries, boots, and other items from freezing. Feathered Friends, Sierra Designs, and Western Mountaineering make bags that fit users up to 7' tall.

  • A few sleeping bag manufacturers offer extra-wide bags or zip-on expanders (like Sierra Designs' Stretch Addition) for some extra room around the middle.

  • Want to zip two sleeping bags together to share some warmth with your tent buddy? Rectangular bags can often be zipped together to form one large sleeping bag, as long as the zippers are compatible. With two mummy bags it’s a little trickier, but still possible. In addition to compatible zippers you’ll need a left- and a right-zippered bag in order to mate the two. Sound confusing? There are a few double-wide sleeping bags on the market (like Kelty's Eclipse Double 35) and Western Mountaineering makes a Summer Coupler that converts their semi-rectangular bags into a double bag.

  • Also, read Gear Explained: Sleeping Bag Shapes, Sizes, Fits.

Temperature Rating

Keeping you warm is probably the main criteria when selecting a sleeping bag. Whether a bag achieves this or not can mean the difference between a restful night’s sleep and the longest night of your life. Choose a bag rated for the season and temperature you’ll be using it in most often.

  • The temperature or comfort rating of a sleeping bag indicates the lowest temperature at which an average user will sleep comfortably. However, everyone sleeps differently. If you’re a cold sleeper consider a bag rated below the lowest temperature you expect to encounter. Hot sleepers may want to adjust upward. Since there is no industry standard for temperature ratings, ratings can and do differ between manufacturers.

  • If in doubt, get the colder-rated bag. You can always vent it by opening the zipper on nights when it’s not as chilly.

  • Temperature ratings assume the use of a ground pad. Since the bottom of your bag will compress under your weight, a sleeping pad beneath your bag will provide more insulation and reduce heat loss through the ground.

  • If you sleep out in a wide range of climates and seasons you’ll probably want more than one bag. Perhaps a 20-degree mummy bag to cover three-season use and a 20-below bag for winter outings.

  • An overbag, essentially a larger sleeping bag that fits over another sleeping bag, can add up to 30 degrees to your bag’s temperature rating, extending a three-season bag into four-season use. Many overbags can be used alone as summer bags, while some add waterproof protection to your sleeping bag. Examples of overbags/warm weather bags include Big Agnes’s Horse Thief 35°, Cross Mountain 40°, and Lost Dog 50°.

  • Sleeping bag liners also can be used to add a few degrees to your bag’s temperature rating. In addition, they help keep the inside of your bag clean, which will extend its lifetime. Examples of sleeping bag liners include Sea to Summit's Reactor, Kelty’s Fleece Travel Sheet, and Marmot’s Trails.

Now head over to Trailspace’s sleeping bag user reviews and product descriptions and soon you’ll be bedding down for some warm, comfy shut-eye under the stars.

Filed under: Buyers' Guides

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October 24, 2014

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