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Chapter 17

Sleeping Bags, Sleeping Pads, and Vapor Barriers

You can endure great hardship as long as you can sleep warm. Sir Francis Galton, from The Art of Travel, 1867


Sleeping bags are great for keeping warm in airports and stations, on overnight trains and buses, and for crashing on a new friend's floor. They are also useful for insulating yourself from El Cheapo Hotel bedding. A good sleeping bag adds more flexibility for the traveler than any other item in the pack.

Of course not all backpackers need a sleeping bag. If you expect to be in a hotel, hostel, or warm train every night you probably don't. If you are hostel-hopping out of a daypack (2000 cubic inches or so) you may not have room. Nevertheless, most backpackers have some kind of sleeping bag.

With my travel style I almost always want a light but warm sleeping bag. I use a twenty-degree down mummy with a standard nylon cover. It gives me tons of flexibility for its weight and volume, which amounts to less than 2.5 pounds and an easy-stuffing 7x14 inches. And for only $140. Some bags are even lighter and smaller. Following is everything I know about sleeping bags, which was learned in the course of buying the wrong bag before my second travel adventure, and this suitable one before my fourth.

Note there is no perfect sleeping bag for all seasons, conditions, or uses. Every bag involves trade-offs between weight, stuff-size, comfort, warmth, weather resistance, and cost. Fortunately the technology has advanced to an admirable state, and with fierce competition (over two dozen American brands alone) quality and value are the rule rather than the exception.


The Mummy and the Semi-Rectangular

For travel the two sleeping bag designs to consider are the two which are the most weight and stuff-size efficient: the mummy style and the semi-rectangular style. Author hot hot hot!

The mummy is the most efficient in retaining body heat since it incorporates a hood which, when fully battened-down, leaves only a small circle of your face exposed to the cold. On warmer nights the hood need not be used.

The roomier semi-rectangular lacks a hood but has a drawstring closure which can be cinched over your shoulders. (A mummy will do this also.) Some semi-rectangular bags have zippers extending across the foot section allowing the bag to open into a comforter, which is a very useful feature. A semi-rectangular will weigh at least five ounces more than a mummy for a given temperature rating, and substantial headgear will also be required to stay warm at that rating.


Choosing the Right Size Sleeping Bag

The roominess of a bag depends upon your and its dimensions across the chest, hips, and feet. A spacious bag will not be as warm as a slightly tighter bag because the bigger bag has more inside air for the body to heat. If the bag is too tight, however, the insulation will become compressed, forming cold spots where your precious heat will escape. Furthermore, if the bag is too tight you will be less comfortable putting on additional layers of clothing should the conditions become extreme for your bag's temperature rating.

Sleeping bags usually come in two or three sizes. The point is if you are 5'5" and carrying a 6-footer's bag you have extra weight, volume, and expense to deal with. It also means you won't be quite as warm as with a better fitting bag due to the extra air space your body has to heat. Shorter folks with long bags should tuck the extra length under their feet.

The only way to properly size a bag is to get in four or five different ones. Outdoor shops allow and expect this. For me, roominess across the shoulders is a paramount consideration since I don't like being too constricted.


Temperature Ratings

Manufacturers give their bags temperature ratings to reflect the low temperature someone can expect to maintain homeostasis, which is a more or less constant, comfortable body temperature. These numbers are somewhat accurate given three conditions which have little to do with the world you and I inhabit.

First, the testing for these ratings is done in rooms where the air remains still. And we all know what an effect wind has on relative temperature (wind chill). In other words, if you are sleeping in the open in a twenty-degree nylon-shelled bag on a twenty degree night with a five mile per hour wind, you will absolutely freeze your butt off since nylon is not windproof.

Second, when testing the manufacturers use abundant insulation underneath the bag--equivalent to a full-length Standard Thermarest, which is 1.5 inches thick and provides more insulation than most travelers carry. Thus if you use a 3/8 inch closed cell foam pad you will definitely feel cold at extreme conditions. (Sleeping pads are discussed at the end of this chapter.)

The final factor is your individual metabolism. In the same bag some folks sleep comfortably while others feel cold. This variation ranges up to fifteen degrees F. Since I sleep on the cold side I would tend to choose a slightly warmer bag for a given condition, which for safety and comfort's sake is a good idea regardless of metabolism.

Note that if you are hungry or dehydrated your ability to withstand cold (or, more correctly, manufacture heat) will be adversely affected. A hot drink and warm stew work wonders on a cold night.


Sleeping Bag Materials

Inner shells are usually made of fine nylon or polyester, although Kelty makes some bags with a cotton/polyester inner liner. Cotton/polyester has less of a sticky or clammy feel against bare skin at warmer temperatures, but it holds water and increases weight slightly. Most good bags have nylon or polyester inner liners which work fine.

Outer shells are made of nylon, ripstop nylon, polyester, GoreTex, Dryloft, Versatec, or other proprietary microfibers designed to provide some degree of water and wind resistance. Nylon is the standard outer shell. It is light, strong, and the most breathable. No regular nylon, however, is better than mediocre for wind and water resistance. Ripstop nylon is stronger, more tear resistant, and also more wind and water resistant. Polyester is more resistant than nylon to degradation from UV radiation, and usually comes in microfiber formulations which are more wind and water resistant. Dryloft is a version of GoreTex specifically designed for sleeping-bag outer shells.

GoreTex and Dryloft sleeping bags are not waterproof--water easily leaks into the many seams. They are good at resisting moisture such as heavy dew, heavy breathing, and spilled beer. Moreover, in real world conditions GoreTex and Dryloft sleeping bags are much warmer than conventionally-shelled ones because they are windproof. This can be important if you expect to be sleeping in the open, or even in a breezy three-season tent. GoreTex and Dryloft add about two ounces to the weight, and are only used in top-of-the-line bags that cost $300 or more.


Insulation Choices

Sleeping bag insulations produce loft between the inner and outer shells. Inside this loft the tiny fibers of the insulation (down or synthetic) create "dead" air space. This dead air space is what keeps the warm air warm, and the cold air out.

In the early 1990's four new synthetic insulations became widely available: Lite Loft, Microloft, Primaloft, and Polarguard HV. The two down insulations, available for millions of years, are grades: good quality 550 fill power and great quality 700 fill power.

The new synthetics are a vast improvement over the old Hollofil, Quallofil, and Polarguard. A good twenty-degree mummy with these new fills weighs about three pounds, compared to about four pounds for the old fills. A comparable down bag weighs about 2.5 pounds.

A three-pound, twenty-degree Lite Loft, Microloft, or Primaloft bag will stuff to about 8"x15", or 750 cubic inches. A similar down bag will stuff to 7"x14", or 500 cubic inches. The down bag thus saves 6"x6"x6" of pack volume!

The North Face twenty-degree Cat's Meow Polarguard HV also weighs three pounds, but its supplied stuff sack is a large 10"x17", or about 1300 cubic inches. This is a durable bag, but much too large for my recommended style of travel.

The allure of synthetics is they maintain ninety percent of their insulating power when soaked with water. They simply don't retain much water, and dry quickly. Conversely, down loses ninety percent of its loft and warmth if soaked, and takes a very long time to dry.

Therefore it follows that wet down could lead to hypothermia and death at one extreme, and at minimum discomfort and aggravation. While I took a down bag through the tropics several times without problems, it was far from the ideal insulator since down absorbs moisture from humid air. On the other hand I didn't need much, if any, insulation, and found it easy to dry the slight dampness under occasional hotel room fans. The real danger comes in cold and rainy climates where everyone must be careful to keep down dry.

Hence synthetics are best for the tropics, cold and very damp areas such as southeastern Alaska and the Pacific Northwest, and for river-running.

Nevertheless down remains the most popular insulation among travel backpackers. It is still twenty percent lighter than the best synthetics, stuffs thirty percent smaller, feels luxurious, and is at least three times more durable. Furthermore, most travelers are able to keep their down sleeping bags dry all the time. My nylon-shelled down bag has been damp a few times, but I've never had a major problem.

A good stuff sack is important, but note that stuff sacks with "dust flaps" are only water resistant, not waterproof. If you are traveling on or around water, lining your stuff sack with a plastic bag and sealing it should eliminate most risk. A well-sealed tent or bivy sack will keep rain from above away, although you should be careful not to pitch it in a low area where water could gather underneath.


How Much to Spend on a Sleeping Bag

In many hostels many backpackers leave their sleeping bags on their beds all day. I often do. And when I do, I'm glad my bag is not a $500 GoreTex superbag. And when my pack is thrown on top of a bus and I don't see it again for a day, I'm also glad my bag isn't so valuable.


Sleeping Bag Care and Maintenance

Never dry-clean any sleeping bag. The risk is too great that a destructive solvent will be used, even if they say they won't. Solvents and fumes may be retained in the insulation, producing skin irritation or an allergic reaction.

Don't put your sleeping bag in a top-loading, agitator washing machine. The agitator could damage it, internally if not externally. Instead, use a front-loading, heavy duty laundromat machine that is usually dubbed "superwasher" or "doublewasher." These machines spin very fast, but they don't use an agitator. Use the warm setting and add a little gentle, easy-rinsing soap such as Woolite or Down Suds.

To dry, set the dryer temperature on low or medium and throw it in. High temperatures could be harmful.

Don't overwash your sleeping bag. Try spotwashing for soiled areas. I wash my bag after several months of use.

Don't store any sleeping bag in its stuff sack longer than necessary. This quashes the loft of any bag. Soon after reaching a campsite, hostel, or hotel, I remove my bag and fluff it with a few shakes. For home storage put it in a large cotton bag, which is supplied with most good bags.


Sleeping Bag Glossary

550 fill power down
Good quality down of which 1 oz. will loft to at least 550 cubic inches.
700 fill power down
Great quality down of which 1 oz. will loft to at least 700 cubic inches. Down ranges from 300 fill power to 750.
Lite Loft
Synthetic insulation from 3M. Made of tiny polyester/olefin fibers bonded together with heat. Has a remarkably soft feel. A good choice if you want an alternative to down. The most popular quality synthetic.
Primaloft
Mixture of tiny and big fibers to duplicate the construction of down. Primaloft PL-1 is said to be the fastest drying synthetic, while Primaloft PL-2 is a less expensive (and less water resistant) version. A good choice for a synthetic.
Microloft
Synthetic insulation from Dupont, made of very tiny fibers. Also a good choice.
Quallofil
Each fiber has seven holes to trap air. Stuffs well, but not known for durability. My Quallofil bag lost half its loft during three months of daily use. Not recommended.
Polarguard
Longest-lasting but huge-stuffing synthetic insulation. Not recommended for travel.
Polarguard HV (High Void)
The continuous polyester filaments of Polarguard have been hollowed 30% to reduce weight and bulk. Still too bulky to be ideal for travel, in my opinion.
Hollofil 808, Hollofil 2
Cheap, heavy, and huge-stuffing insulations. Only useful for low-priced car-camping and backyard bags. Not recommended.
Dryloft
A version of GoreTex designed specifically for sleeping bags. It has twice the breathablity of regular GoreTex--thus insulation is less likely to become damp from perspiration under cold and damp conditions. Dryloft also makes a bag windproof.Flat hood example
Sculpted hood
Found on better mummies. Provides superior comfort and seal around your head as opposed to the more cheaply made flat hood pictured right.
#7 and #8 zippers
These are the most common sleeping bag nylon coil zipper sizes. Regardless of the manufacturer, two #7's or two #8's can usually be zipped together in some fashion--though it may not be a heat-efficient combination. But then that isn't always the primary consideration.
Left zip/right zip
A sleeping bag with a zipper on the left side mates best with a right-zipped bag of the same model. If you tend to sleep on your left side and/or write with your right hand, you may want a left-zippered bag. Right-sided sleepers and/or left-handed writers may want a right zip.
Stuff sack
Coated nylon sack for carrying sleeping bags. For canoe or flimsy bridge travel, line the inside with a plastic bag and seal it tightly. Hydroseal makes waterproof stuff sacks. If the stuff sack is too small for your bag the daily stuffing ritual becomes aggravating, and causes unnecessary damage to your loft.
Left: Campmoor 20° F. mummy with sculpted hood and stuff sack.
Compression sack
A nylon stuff sack with webbing which reduces stuff size by 30% when cinched. Only recommended for an old, ugly bag you happen to have, since compression sacks permanently quash loft.
Down Suds
A gentle, easy-rinsing soap for down products. Costs about $2.50 from outdoor shops. Woolite also works.


Twelve Sleeping Bags Compared

These are representative of the market--your local outdoor shop will have similar bags. Temperatures are in Fahrenheit, and may not compare from one brand to another. All measures are as claimed by the manufacturers.

Campmoor +20 Mummy
$140, 2 lbs. 4 oz. Mummy. 550 fill down with nylon inner and outer lining. Stuff sack: 7x14". Cut wide at the shoulders (32"), but of average, slightly-constricting mummy-width from the knees on down. Not a great bag, but a good bag that has served well on my last four trips. My personal rating for my bag is about +30° F. (Pictured above.)
Campmoor +45 Down Lite Tapered
$110, 2 lbs. Semi-rectangular. 550 fill down with nylon inner and outer lining. Stuff sack: 6.5x14". Zip extends across the foot section, allowing the bag to be opened into a comforter. A compact and light choice for the fair-weather hostel-hopper.
REI Nod Pod +15
$140, 2 lbs. 14 oz. Mummy. Lite Loft with nylon inner and outer lining. Stuff sack: 8"x18". Has a shoulder collar which can be tucked away when not needed. Has 60% of its insulation on top, 40% on bottom.
Eastern Mountain Sports MM +20
$190, 2 lbs. 10 oz. Mummy. 550 fill down with nylon inner and microfiber outer linings. Stuff sack: 7x14". Microfiber on this bag resists moisture better than regular nylon.
North Face Blue Kazoo +20
$200, 2 lbs. 5 oz. Mummy. 550 fill down with nylon inner and outer lining. Stuff sack: 7x14". A top-selling bag for many years. Has a narrow cut for maximum warmth and minimum weight. Get in one before you buy.
Western Mountaineering Apache sleeping bagNorth Face Foxfire-DL +5
$420, 2 lbs. 14 oz. Mummy. 700 fill down with nylon inner and Dryloft outer shell. Stuff sack: 7x14". Good for mild winter camping.
Western Mountaineering Apache +20
$255, 2 lbs. 2 oz. Mummy. 700 fill down with nylon inner and outer lining. Available in 5' 6", 6', and 6' 6" sizes. Stuff sack: 7x14". These bags are prized by travelers worldwide. (Perhaps too prized--pictured right.)
Sierra Designs Calamity Jane +20
$150, 2 lbs. 15 oz. Mummy. Lite Loft insulation with polyester inner and outer lining. Stuff Sack: 8x18". Sized for women, with extra insulation for the feet.
Sierra Designs Lite'N Up +20
$150, 2 lbs. 15 oz. Mummy. Lite Loft insulation with polyester inner and outer lining. Stuff sack: 8x18". It stuffs easily. 30.5" width across chest. A popular bag by a top manufacturer.
Caribou Early Frost +20
$165, 3 lbs. 2 oz. Mummy. Primaloft insulation with nylon inner and outer lining. Stuff sack: 7x14". 32" width across chest.
Moonstone Minima XL +30
$210, 2 lbs. 1 oz. Mummy. Lite Loft with nylon inner and outer lining. Stuff sack: 7x14". Has a fairly roomy cut across chest (31") and is sized to fit travelers at 5'9" and 6'4". The Moonstone Optima XL is rated at 15 degrees.
L.L. Bean Ultra Lite Loft +40
$90, 1 lb. 14 oz. Mummy. Lite Loft with nylon inner and outer lining. Stuff sack: 6.5x12". This is a good bag for the tropics, hosteling, and summer desert hiking.
U.S. Army and NATO issue
Available for 10-$20 in surplus stores, weight is around five pounds. Heavy duty, but the insulation is likely to be worn-out. (Which is why they're surplus.)



Sleeping Pads

The primary purpose of a sleeping pad isn't comfort, but to insulate yourself from Mother Earth so she doesn't suck all the heat out of you via conduction. When nighttime temperatures fall into the 50's and lower, you need a sleeping pad to overcome this powerful, heat-robbing effect. Of course only camping travelers need a sleeping pad.

Sleeping pad in great outdoors. Photo: With a sleeping pad you'll be comfortable waiting for the train or enjoying a night in the wide open.

For general spring, summer, and fall travel two products stand out: Cascade Designs' Therm-A-Rest Staytek Lite and the GVG Pack-Mat Lite. These are open-cell foam pads with waterproof covers. You open the valve at one corner and within a minute or two they magically self-inflate. They have double the insulating power and are thicker and more comfortable than most closed-cell foam pads. You can blow in a few breaths to make it firmer and significantly increase insulating power, or let out air to make it softer.

Their best feature, however, is that they roll-up small enough to fit inside your pack. Thicker and heavier models are available, but are unnecessary for spring, summer, and fall travel. For camping in winter conditions you can use a self-inflatable in conjunction with a full-length, 1/2 or 5/8 inch closed cell foam pad.

Regular closed-cell foam pads are lighter and cheaper (about $10 and 12 oz.), but they consume two to four times as much volume, requiring that they be lashed to the outside of the pack. After getting on and off a few crowded buses and subways, you'll be happy to have spent the extra money on a compact, self-inflating pad.


Sleeping Pad Repair

If you cannot find a leak by sight or sound, fill the pad with air, close the valve, roll-up half the pad and put pressure there with your knees. Then pour a little water on the remaining portion to check for air bubbles. Repeat on the rest of the pad until the leak is found. Otherwise you'll need a tub. Repair with nylon tape or rubber cement.


Six Sleeping Pads Compared

Therm-A-Rest Ultra Lite II 3/4
$47, 14 oz. 47x20x1" (that's one inch thick). Rolled size: 5x11". Short length leaves the feet without insulation, but most users place clothes or their pack under their feet, if necessary. I have happily used the previous "Ultralite 3/4" model for over four years.
Therm-A-Rest Ultra Lite II Long
$60, 30 oz. 72x20x1". Rolled size: 5x11". Padding for your feet, if they need it.
Therm-A-Rest Staytek Long
$62, 40 oz. 72x20x1.5". Rolled size: 5x21" (It can also be rolled to about 8x11".) This thicker, full-length pad will go a long way toward keeping you warm while winter camping.
GVG Pack-Mat 3/4 Lite
$55, 13 oz. 47x20x0.8". Rolled size: 4x11". Made with a non-slip polyurethane cover. This French-made pad is the lightest and smallest-packing self-inflator. Popular in Europe, but hard to find in the States.
GVG Pack-Mat Long
$65, 20 oz., 71x20x0.8". Rolled size: 5x11.
Generic closed cell foam pad
From 6 to $16, from 8 to 14 oz., various sizes. Range in thickness from 1/4" to 5/8". They are light and cheap, but not compact--all must be fastened to the outside of your pack. If money is tight, take heart that many camping travel backpackers use closed-cell pads and get around fine. For summer travel try cutting a thin 1/4 or 3/8 inch pad to just what you need.
No pad
A pad is not absolutely necessary for campers in hot climates like Greece and Spain in the summer, except for the mountains.
Therm-A-Rest Repair Kit
$5, 1 oz. Contains adhesive, instructions, and patches for repairing pads, tents, sleeping bags, and jackets.


Vapor Barriers
Or,
What to do in face of bone-freezing cold and howling Jupitian wind


If for some reason you must spend a night at a temperature far below your sleeping bag's rating, a vapor barrier could save your life. First, put on all your clothes, but you must have good quality wicking fabrics next to your skin. Then get inside the large garbage bag you have been carrying for emergencies, and wriggle inside your sleeping bag in an area as wind-protected as possible. Pull the garbage bag tightly across your chest or neck so little air can escape. Your head, of course, must always remain outside the garbage bag.

This system dramatically reduces evaporative heat loss because your body adjusts to the high humidity micro-climate inside the plastic bag. The wicking action of your clothes prevents your skin from becoming damp and cold. However, if the layer next to your skin is cotton, water will not wick away and you may freeze to death from your own perspiration.

You can also line the inside of your sleeping bag with an aluminum space blanket, or put bread bags over your feet. I used the space blanket/sleeping bag combination with success in late fall Germany and Czechoslovakia when both overnight temperatures and my synthetic loft simultaneously plummeted. Some mountaineers routinely employ vapor barriers since they add twenty to thirty degrees of protection for almost no weight.


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How to See the World on $25 a Day or Less is copyright © John Gregory 1995, 1996, 1997. Except for personal use (like showing to a friend), it may not be reproduced, retransmitted, archived, or altered without author permission (
webmaster@artoftravel.com) Permission to link and review is freely granted. All product names and trademarks are property of their owners. Updated February 16, 1997. Thank you.

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