The Mountain Hut
Sleeping Bag Strategies
8000-10,500ft hike, expected morning temp of 25F-32F in persistent overcast cloud cover or weather. You need synthetic here. Bring a -15 to a -0 synthetic bag, and something to keep water off of it.
8000-10,500ft hike, expected morning temp of 15F-24F in persistent overcast cloud cover or weather. You can get away with bringing a down bag here, but synthetic excels in this range. Down will also offer a lighter pack, and less bulk too.
Mt Whitney Winter, 7000ft-14,900something feet. Morning temp of 10F or below with bright sunny skies. This is down country. If you get any kind of weather your going to pray for a -15 or more Down bag, that has a Gore-Tex outer shell built in, or a Bivy Sack that you can place your sleeping bag into if you didn't bring your Down Bag on this trip.
If you have the built in Gore-Tex outer on your bag, and have either a fly-sheet, or a Bivy sack for an outer bag shell protection layer, then you don't even really need a TENT. Bivouac-sack trips are not uncommon in the winter mountaineering world. Sometimes bivy'ing can even be better given the strength of the winds that bend fully guyed out Easton 7075-T9 aluminum alloy aluminum tent poles. If your poles start bending, this would be the exact point where you would want to start to take anti-rip measures quickly before tears begin if anything gets offset. Set those tents up properly to rely on your bag completely.
I've been known to go on mountaineering hikes with no tent, just a bivy and a synth-bag for shelter instead of the tent. But you soon learn that a tent is a must in this blowing snow environment.
A good way to increase the warmth of your bag even more is go purchase a "bag liner" these usually SUBTRACT about 10-15 degrees from your bags temperature rating. If you have a 15DegF bag, and want to make it a 0F bag, then buy a synthetic liner and place it into your sleeping bag before retiring for the night. Liners are also washable, help to wick away moisture to the next layer which in this case is the sleeping bag itself, and offers a better feel on your skin. This liner too has a drawstring sometimes eliminating the need to use your bags drawstring, which offers you more maneuverability. It's also much easier to toss and turn with this slippery liner. One not-so-interesting phenomena that happens when using a liner is if your not on a completely level surface, you will wriggle your way clean off your sleeping area and wake up to a completely twisted and snagged bag that's full of cold spots since its no longer lofting due to contortion. If your going to get a bag liner, a good bag to have is a 0degF rating, which with the liner becomes a -15DegF bag. This is plenty in some of the coldest environments. Remember, when doing your calculations, the tent adds usually about 10-20 degrees to the outside temperature in less than windy conditions. So say for example, you have a 0F deg bag, and a 15F degree liner. You have a -15F setup, and the tent brings your comfort level another 10-20F below that(not inc. wind chill, which brings those numbers considerably higher), now giving you a comfort rating all the way down to about -30F. This is good for all but the most extreme trips, unless your expeditioning to the near Arctic, near Antarctic, or above 14k Feet.
Another good thing to remember is all these temperature calculations are based on when sleeping with the minimum thermal layer, and no insulating layers on your body except for feet and head. Normally this is the minimum that is needed. Think of your bag as one big dead-air-space insulator(or cocoon) that lies just over your bodies thermal protection layer. The fact that all the calculations are based on having on ONLY thermals allows for you to throw on additional gear furthering your body comfort temperature rating down by the ten's. For instance, put on your down jacket, and you just brought your upper torso comfort range from -30F to about -70F. You will be too hot body-wide most assuredly. Your bag will be a smokestack of precious moisture loss, dehydrating you out as you sleep and wetting the down as you naturally steam your water vapor off.
This brings us to a very-interesting sleep phenomena called Tent Snow! Should you not obey the general guidelines above, and accidentally place on too many layers, you will be awaken to a very unpleasant experience. You will wake up with ice or rain falling onto your face, frozen ALL over the tent walls and ceiling, tent floor, and tent gear, have snow all over your bag, and witness ice slinging off the tent walls into your face at the very speed of the outdoor wind, all morning. This of course also has the added benefit of eventually melting and fresh-water-laundering things in the tent. This is a common occurrence, and points to a misjudgment in choice of clothing during a nights sleep. Even worse, you may wake up to tent rain, if its warm enough. IN this case, almost everything in the tent gets mostly soaked. One is lucky if they can wake up in time to unzip the door just in time to freeze the tent rain into tent icicles without waking up with a soaked sleeping-bag top at the very least. Its your bodies sweat at the expense of your cellular hydration, that has created all this internal tent snow. I would not recommend sleeping in down garments either way. Sleeping in them will reduce the integrity of the feathers and loftiness, and also make it uncomfortably warm in all but the most inhospitably cold lands. Examples of these few places where you might want to sleep with a down insulating layer on would be Arctic zones such as above 12,000 feet, northerly or southerly of the 66th parallel where the Tundra begins, or when you find that the mercury is dipping probably below the -45F range as exposed to the wind chill on the outside of your bag. I use my down jacket particularly for a head and shoulder wrap only, that way i don't need to tighten the drawstring if its above 0 to -10F. A good item that IS good to wear for extra warmth in the bag would be your synthetic-insulators at that point, should you feel a little chilly in your already -30F setup.
Again, make sure your head is being kept warm, and be sure to have something UNDER the feet portion of the sleeping bag to help keep the feet stay warm. You don't want the foot end even within 2 inches of the ground. Some good items to place your under your bags foot could be your backpack or wadded up shells since feet are hard to keep warm in the night for alot of people.
As you notice, there's more to a bag than first meets the eye. If you pay attention to all the details, then your winter mountaineering or expedition experience will have one of most important elements, Warm and Toasty Nights! Simply put, if you play your cards right, your sleeping bag will perform as planned and take care of you, so take care of this integral piece of backpacking equipment with the best of your abilities. My 0 degree Quallofil has lasted me over 10 good years of service now. Of course the zipper has blown out by now, and when its time to hit the big mountains, I would simply grab the Eddie Bauer Down -15F bag, possibly with a Gore-Tex outer even. North Face makes top quality bags, but they are on the high price end. REI.com is always an excellent choice for mountaineering gear information and purchases as well as Cabelas.com.