Gain knowledge to research and buy the correct sleeping bag

A sleeping bag isn't generic for all people. What bag you buy should depend on your body type, personal preference, backpacking climate, and other variables. Before forking out money to purchase this expensive item, be sure to research what exactly you want, read reviews, and shop around. With hundreds of models to choose from, you don't want to be lying there all night not being able to fall sleep because of your sleeping bag.

Choosing a Sleeping Bag

Sleeping bags keep you warm by trapping and holding a layer of "dead" (non-circulating) air next to your body. This air, which is warmed by your body heat, forms a barrier between you and colder air or cold surfaces.

When evaluating bags, consider these key factors:

• Comfort rating
• Insulation (down or synthetic fill)
• Weight
• Size when compacted
• Shape

Comfort Rating

A sleeping bag's temperature or "comfort" rating identifies the most extreme temperature the bag is designed to accommodate. When you hear a bag described as a "+20 bag," it suggests most users should remain comfortable if the air temperature drops no lower than 20 degrees Fahrenheit.

Are such ratings infallible? No. Humans all have different metabolic rates, and no industry standards exist that uniformly determine sleeping bag comfort ratings. Instead, each manufacturer assigns a rating to its bags based on its own research. Therefore, use these numbers as a guide, not a guarantee. If you have trouble deciding between two bags, it's not a bad idea to select one that offers a little more warmth than you think you might need.

Many factors affect your ability to keep warm inside a sleeping bag:

• Sleeping pad (when sleeping on frosty ground at high elevation, you need a full-length pad to keep you separated from the cold; when sleeping on snow or frozen ground, two pads are recommended)
• Tent (a tent or bivy shelter traps an extra layer of dead air, warming it by up to 10 degrees)
• Metabolism; you might be a "cold sleeper" (and thus one who prefers extra insulation when sleeping) or a "warm sleeper" (someone who kicks the covers off at home)
• Gender (women frequently prefer warmer bags than men)
• Clothing worn while inside the bag (dry long underwear and clean socks are good choices on cold nights, plus they help keep body oils off your bag; a cap and neck gaiter keeps body heat from radiating away; fleece pants and jackets help on colder-than-expected evenings)
• Adjustments you make while in the bag (keep the bag zipped up and the hood cinched on cold nights; be careful to not breathe into the bag, since moisture has a negative effect on the insulation)
• Food in your stomach (the process of digestion helps produce warmth)
• Hydration (if you're not well hydrated the food won't help much)

Tip: To be ready for those extra chilly nights, select a bag with a temperature rating that slightly exceeds the low end of the temperature range you expect to experience. If a +20° F bag sounds right for you, a +10° bag would probably work well, too. On warm nights, you can always vent a bag (by using the double zipper to open the area near your legs) or simply drape it over you, unzipped. It never hurts to be a little over-prepared.

Recognizing that comfort ratings are merely general guides. Sleeping bags are organized in the following categories:

Note: Even in summer, a +35° bag may leave you feeling chilly when sleeping in the high country. If you think of yourself exclusively as a warm-weather camper, yet plan to routinely camp at higher elevations (3,000 feet and up), choose a bag with a comfort rating at least in the 20s.

Types of Insulation

The main decision in purchasing a sleeping bag is choosing between the two types of insulation or fill: down and synthetic. Goose-down fills are very light, compressible, durable and breathable. While initially more expensive, they offer great value over the long run. Synthetic fills excel in damp, cold conditions and come with a lower price tag. They are slightly heavier and less compressible than down, but do a great job of trapping body heat.

Down

Down is the wispy, fluffy undercoating found just beneath the outer feathers of geese and ducks. This natural fiber is an extraordinary insulator.

Down's positives include:

• It offers tremendous warmth for surprisingly little weight (thus offering a superior "warmth-to-weight" ratio).
• It can be compacted into very small sizes.
• Its effectiveness outperforms synthetic insulation by years - even decades.

Down, though, does have a downside:

• If it gets wet, it is of no value until it dries - and in the field, that can take a long time.
• It is more expensive (keep in mind, though, that its resistance to deterioration makes it an outstanding long-term value).
• Down is graded according to fill power - meaning the number of cubic inches one ounce of down will displace. The higher the number, the better the insulation.

Synthetic Materials

Synthetic materials are basically plastic threads (extruded polymers, to be technical). The threads are most commonly a continuous filament (a long, single strand). They can also be arranged in short "staples" up to four inches long. Usually the threads are hollow, reducing their weight and enabling them to trap more air.

The advantages of synthetic fill include:

• It still provides some insulation when wet
• Synthetic materials dry fairly quickly.
• It's less expensive than down.
• It's non-allergenic.

The shortcomings of synthetic fill are:

• It's bulkier than down (so it takes up more space when you're carrying it).
• It's heavier (it takes more weight to get the same warmth down provides).
• The filaments gradually degrade over time.
• The insulating "batts" of filaments are stiffer than down and do not drape over the contours of your body as effectively.

Down works well for just about everyone except people who frequently find themselves in rainy conditions. Synthetic insulation is a good choice for kids and newcomers to camping and backpacking. Down always wins in terms of weight, compressibility, warmth and durability. Yet the value and performance of synthetic bags makes them very popular.

Shell and Lining

The outer shell of a camping bag is typically made of a ripstop nylon or polyester for durability. Many synthetic-fill bags feature a shell fabric treated with a Durable Water Repellent (DWR) finish. DWR is the stuff that allows water to bead up rather than soak through the fabric. Linings, on the other hand, should promote the dispersal of body moisture, so DWR is not used here.

Tip: How can you tell if a shell has a Durable Water Repellent (DWR) treatment? Rub a wet cloth across the surface of a bag. If the water beads up, then it has DWR.

Shape and Fit

The shape of a bag certainly affects your sleeping comfort. All true backpacking bags are mummy-shaped, but some roomier camping bags can double for use in the backcountry (these tapered bags are usually categorized as semirectangular bags). To compare sizes, look for the shoulder and hip girth specs of the sleeping bag.

• For maximum heat efficiency and less weight, choose a mummy bag with narrower shoulder/hip measurments. Realize though that the tighter the bag, the more restrictive it is.
• If you have a broad frame or are a restless sleeper, consider mummy bags with larger shoulder/hip specs or semirectangular bags for greater comfort. These bags are a bit bulkier and heavier, though.

In the last decade or so, sleeping bag options for women have increased dramatically. These bags are specifically designed and engineered to match a woman's contours. When compared to men's bags, women-specific bags usually have the following characteristics:

• Shorter in length
• Narrower at the shoulders
• Wider proportionally at the hips
• Occasionally, extra insulation in the upper body and/or footbox

Bag Length

What about length? Do you need a "regular" or "long" model? The general rule is as follows: If you are no taller than 6 feet, choose a "regular" length bag. If you are up to 6-feet-6, you want a "long" bag.

While men's bags can fit both men and women, women-specific bags have different sizes to accomodate a woman's body shape. A "regular" size in women's is generally equivilant to the men's "short."

Storage

You can prolong the life of any sleeping bag by hanging it in your garage or storing it loosely in a cotton storage sack - and not rolled up tight in a stuff sack. This prevents the insulation from getting permanently compressed, which reduces its insulating properties.

Additional Resources

• Trailspace - Guide to Sleeping Bags
• REI: Expert Advice - How to Choose a Sleeping Bag for Backpacking

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