One of the most important items of equipment to consider before going on a trek or a climb is a sleeping bag. A good sleeping bag can make or mar a trek - if it is not warm enough, you will spend the whole night cold and shivering and will be tired the next morning for the day's walk. So how do we choose the right sleeping bag? Here are some pointers to be taken into consideration:
All good sleeping bags are temperature rated. The top of the line bags from companies like Marmot, Western Mountaineering, North Face etc. will also have the EN rating which is most accurate. Normally summer sleeping bags will be rated 0 to +10 Celsius, three season sleeping bags will be -10 to 0 Celsius, four season or winter bags will be -20 to -10 Celsius. The rating given by the company is supposed to be the lowest temperature which will keep an average sleeper warm. However, there are warm sleepers and cold sleepers so depending on the sort of sleeper you are, you may need to choose your bag. As a thumb rule, buy a sleeping bag five degrees Celsius below the lowest temperature you plan to encounter. So if you plan to be in -5 Celsius buy a -10 Celsius bag! A sleeping bag's temperature rating can be extended by using a liner inside but that would add to some additional weight to the bag.
Broadly speaking, there are two types of insulation - synthetic and down. Synthetic is usually cheaper and comes under a lot of names - Primaloft, Polaguard, Thinsulate etc. Down can also of various ratings like 600 fill, 700 fill, 800 fill etc. In a nutshell, a down bag will usually be lighter and pack smaller than a synthetic bag of the same rating. It will also usually be more expensive than it's synthetic counterpart. However, down has a major drawback, if the bag gets wet then it is useless - it loses its insulating properties. So if you are going on a trek and expect lots of rain and snow, down may not be the best choice. Recently, a new type of down has been introduced called "Dri Down" which is supposed to insulate even when damp or wet!
Broadly speaking they would be rectangular and mummy. The rectangular bags would have more room inside to toss and turn but usually the mummy bags would be warmer for the same weight and are preferable for high altitude treks.There are also bags with full zips and half-zips. The half zip ones would be lighter, but may be difficult to get in and out of!
If you are carrying your own backpack, then weight is very important. The lighter sleeping bags will usually be more expensive than the heavier ones for the same temperature rating. I would suggest not to go beyond 3 lb in weight for a three season bag - in fact some of the good bags would range well below 3 lb.
Most sleeping bags will give you a packed size e.g. 7" x 13" and so on. The larger sizes e.g. 13 " x 20" would be very bulky and difficult to pack in a backpack. On one of our South Col treks, I saw a client's sleeping bag which took almost half the space in a 50 litre duffel and left very little room for anything else! So check the packed size before you buy. Generally down bags will pack smaller than synthetic bags because they are easier to compress.
Some of the great sleeping bags which I have used in the last thirty years in the mountains:
The North Face Blue Kazoo - almost a legendary bag, North Face has been manufacturing this bag for more than fifteen years now keeping the price and weigh more or less constant! It is often available on sale for less than US $ 200! Highly recommended for a good three season bag and if properly cared for can last a lifetime!
The Marmot Pinnacle
I am presently using this bag for the last couple of years - excellent loft, warmth to weight ratio and super light and compressible - it is filled with 800 fill power down. A highly rated bag though a bit on the expensive side! Marmot have stopped production of this bag which is a pity! The Meteor looks like the replacement for the Pinnacle! https://www.youtube.com/watch?v=RN16Vt2cgco
Generally for spring and autumn trekking in the Himalaya a three season bag is usually fine. If you are planning to trek in winter, e.g. Chadar trek, then you need to have a four season bag.
Sleeping Bag Resources
How to Care for a Sleeping Bag
Some top Sleeping Bags
Down vs Synthetic Sleeping Bags
How to wash a down sleeping bag in a washing machine?