Choosing a Sleeping Bag
Choosing a sleeping bag requires one to make a choice in a couple of different areas. The two primary considerations are whether you will be packing your bag via a backpack, and secondly, what temperature conditions will the bag need to cover you against. We will cover these factors in detail, and then we will also discuss factors like fill material preference, shell material preference, shape (mummy or rectangular), and dimensions of the sleeping bag.
We will start with a little history of sleeping bags. To the best of my efforts, I have been unable to find evidence of the manufacture of sleeping bags pre-Civil War era. In fact, it appears that the first commercial sleeping bag manufacturer may have started operation in the 1890's. All of this began in Europe. Prior to the use of sleeping bags, bedrolls were the order of the day.
The first big usage of sleeping bags was by mountaineers. Their sleeping bags were very crude compared to today's. Obviously the purpose of their sleeping bags was to be light enough to carry and to keep them warm. These kind of considerations are where your choice of a sleeping bag should begin.
Is Weight a Consideration?
I do not want to oversimplify things here, but a good starting point to narrow down choices, is whether or not you need to rule out sleeping bag choices that are too heavy to pack on a backpack. Sleeping bags that weigh as little as two pounds are available, but at a price. The lighter the bag, the harder (and more expensive) it becomes to purchase one with a low temperature rating. If weight is not a factor because you will not be backpacking, your choices expand greatly.
What Temperatures Will Your Bag be Used In?
The purpose of a sleeping bag is to keep you warm. The purpose of camping is to have fun. It is difficult to have a fun and have an enjoyable time when freezing through the night. I suggest not wasting your money on any sleeping bag that will not keep you warm. So how do you know if sleeping bag will keep you warm?
The problem with ratings used to be that there was no set standard. Recently this has changed. There is now an EN (European Norm) rating system that has made an attempt, and a pretty good one at that, to establish a better and more consistent rating system.. no rating system is without flaws, but this one gets close.
The temperature rating you should look for is the minimum you expect to encounter on the trips you will take. For example a 20 degree bag should keep you comfortable down to that temperature. Also factor in how you sleep. For some, a 20 degree F bag will keep them warm down to a much lower temperature, while for others, it may not even keep them warm at the EN rated temperature.
Mummy Bag or Rectangular Bag
Mummy bags are generally the ones that are available for colder conditions and are made in lighter weights for backpacking. They also tend to be more expensive and also can be difficult to fit into for larger people. Make sure that when considering a mummy bag, if you are larger, read the bag's dimensions. Mummy bags are made in a variety of lengths and widths.
Here are the basics. Down fill used to be the only way you could get the warmth you needed for extreme temperatures. The sacrifice you made with down, was that if it got wet, its thermal insulation capacity was almost non-existent. Now, some down bags are treated to minimize lost insulation when damp. Down packs down and it weighs much less. It is the typical material for backpackers for this reason. Down comes in different qualities...the higher the number the greater the loft...equating to greater warmth.
There has been an improvement over time in synthetic materials. Down is still the gold standard, but comes at greater cost and with the downside of lost insulation when wet.
Typically, any good sleeping bag will have a shell made of polyester or rip-stop nylon. One additional feature that can be important is water repellency. While there are bags on the market made with gore-tex and similar breathable water -repellent fabric, the reviews I have read have not been so great. At this stage, I would stick with the water-repellent materials.
In better sleeping bags, men's and women's cut bags are available. As you may have noticed, men and women are shaped differently. These bags represent those differences.
Also, length is a consideration. Get a bag that fits you. In men's bags, the lengths are generally short (up to 5'6"), regular (5'7"-6'), and long (6'1"-6'6"). If you are taller, there are bag manufacturers out there for you. Look around.
For length in women's bags, the sizes are generally regular and long. Regular runs up to around 5'6" and long runs from 5'7" to 6'.
As previously mentioned, if buying a mummy bag, make sure the lateral dimensions will fit your body size.
There are other factors you may need to look at. Some of these include zipper type, hood design, bivvy sacks, etc. The information in this article is a good starting point to get you out there (or online) looking for what you need.