Quote from Appalachian Mountain Club WINTER CAMPING Second Edition; “During the eight hours or so that we are asleep, our bodies expel water vapor – approximately one pint of water per night. This moisture is insensible perspiration and occurs even when you aren’t sweating but are merely at rest.” This moisture passes from the body into the fill of the sleeping bag, compromising its insulation value.
• How warm a bag is depends upon the thickness of the fill. The thicker the fill, the more dead air spaces are created to trap warm air.
• To keep its loft evenly distributed, shake your sleeping bag each time you use it.
• To extend the life of the bag, it is best not to store the bag for long periods inside its stuff sack. Hang your bag, or use a storage sack designed for sleeping bag storage; bag stores loosely inside a larger storage sack.
• Warmest fill per given weight
• Provides about one-third more insulation than the same amount of high-tech synthetic fiber.
• Compresses more compactly than synthetics
• If well maintained, can last twice as long as fiber-filled bags.
• Absorbs moisture rapidly and the loft collapses when damp. Not a good choice in damp weather.
• Three choices of fill material; Quallofil, Hollofil, Polarguard.
o Retain much of their insulation value when wet.
o Dry quickly.
o Cost about half as much as a comparable Down bag.
o Can be bulky and add extra weight to carry.
o When winter camping, go with a Mummy bag.
o Contour the body closely, most efficiently shaped sleeping bags, most warmth.
o Insulated hood can be drawn around the head, keeps warm air inside the bag.
o Look for a Mummy bag with a well-insulated draft tube that lies against the full length zipper to keep cold air out.
o Make sure bag has an insulated collar that wraps around your neck to prevent the escape of warm air and the entrance of cold air.
o Roomier, but heavier and colder when winter camping.
o If cold weather camping, you can fill the extra space at the bottom of your rectangular bag by filling with clothing, or put your boots inside a plastic bag and store inside the bottom of your sleeping bag, creating less space to heat.
• Choose a bag that is comfortable but is not too large or too small.
o Your body has to generate extra heat to warm up empty air space.
o If bag is too small, movement is restricted.
• There is no industrial standard rating system for comparing the bags of different manufacturers.
• Different people have different metabolic rates, requiring different ratings for each individual.
• When you are not sure what rating to choose, go with the warmer bag.
• You can use a thinner summer weight bag inside of a three-season bag for added warmth; however it adds more weight and bulk for carrying.
• The rating on bags can be deceiving. Just because the bag is rated at 20 degrees, does not mean you will be warm and comfortable in your bag at that temperature. Adding another bag or liner inside of your sleeping bag will add to your rating and keep you warmer.
Sleeping bag covers
• Coverings of waterproof breathable fabric keeps your bag from getting wet from melting snow inside snow caves, from spindrift if you are sleeping under a tarp, or from the snow that is drug into the tent.
• Keeps moisture from penetrating your bag from the outside, keeps wind from stealing your warmth, creates another layer to trap warm air.
• Moisture condenses as frost between your bag and the bag cover. Must be brushed off every day, or frost can work its way back into your sleeping bag.
• Inner bag liners, non-breathable material.
• Keeps your sleeping bag insulation dry during the night.
• Can add measurably to the rating of your sleeping bag.
• Three basic types; open cell, closed cell, air mattress.
o Open cell – comfortable if thick enough. Compress easily. Need to be at least one-and-one-half inches thick. Absorb moisture like a sponge.
o Closed cell – don’t compress easily, so you can go with a thinner (3/8 inch) pad. On very cold nights, you’ll want more insulation. They don’t absorb moisture.
o Air mattress – most comfortable sleeping pad, but quickly drains your body heat away. You can use an extra foam pad on top of the mattress, or use a mattress with open cell foam inside the air chamber such as a Thermarest brand. Air mattress can puncture so bring along a repair kit.
o Cold ground will suck the warmth out of you.
o Put insulation between your sleeping bag and the ground. The more the merrier!
o Putting your pack under your legs and feet adds insulation. Arrange a layer or two of wool or pile under your head and shoulders will also add to the efficiency of your sleeping pad.
o A wool blanket between your sleeping bag and your sleeping pad will add another layer of insulation.