The sleeping bag is a critical piece of camping equipment that is often overlooked. As anyone that has spent the night above the snow line huddled against their packstove for warmth can tell you, it is critical that you select the right bag for what you are planning on doing. There are many different types of sleeping bags out there and their uses are as varied as the colors of leaves in autumn so selecting the right bag can be a challenging experience. This simple guide is designed to give you a leg up and simplify this experience.
Styles
There is generally two main styles of sleeping bags, the standard rectangular sleeping bag and the mummy bag. The regular rectangular sleeping bag is good for moderate temperatures down to about 40F. Much lower in temp and regardless of filling that draft through the top is going to be murder. For lower temperatures the mummy bag is the best bag you could hope for. The mummy bag is called such because when you are bundled inside it you look like a mummy with virtually nothing showing of the person inside. Mummy bags have the disadvantage of space though. If you are a larger individual, make sure to try the bag before you buy it. Mummy bags are designed to be tightly zipped and the drawstring pulled in tight. I have spent the night in a mummy bag with nothing more than my nose poking out.
Filling Material
Thanks to modern chemistry there are a large number of potential filling materials for your sleeping bag. Each has its advantages and disadvantages. In addition there is also the always present feather down filled bags. All the materials work with the basic priciple of keeping a layer of air trapped inside the insulating material between you and the environment outside. Your body heat warms this air and the insulating materials keep that warm air from escaping making for a comfortable night regardless of outside conditions.
The primary materials for synthetic materials are Hollofil II and Quallofil. Some manufacturers may have other materials as well but these are the standards. Hollofil II is the lower cost, higher weight, less insulating material with Quallofil being a better insulator (i.e. lower weight). Goose down is a common material used in many high end sleeping bags. Down is a great insulator but if it gets wet it loses much of its insulating properties. If there is even a slight chance of it getting wet go with the synthetics. Down also has the disadvantage that if it does get wet and gets put away without being properly dried, you will never get rid of the smell of wet feathers. Ever.
Synthetics have a slightly higher weight but in my opinion it is worth it. One time when I was camping we had a rain storm hit us. I was in a synth bag and stayed cozy warm even with over an inch of standing water in the tent and me soaked to the skin. I only noticed when my companion who was in a cotton bag woke me up and forced me out.
Temperature Ratings
Good quality sleeping bags come with a temperature rating on them to let you know the temperature range in which an average person will be comfortable. If there is no temperature rating then chances are its designed for summer like conditions only. It is important to note that if you buy a sleeping bag rated for a very cold temperature and it is warm out, you are likely to be uncomfortably warm. A bag rated for below zero temperatures will be uncomfortable above 45F as a general principal. Temperature ratings are very important if you are going to be in cold areas particularly during Fall or Winter months. Most of the time temperature ratings are spaced in 10-15 degree increments. For example 45F, 30F, 15F, 0F, -15F, -30F are common ratings and increments. The colder the bag, the heavier and more expensive the bag is going to be. It should be noted that a good set of thermal underwear can make allow you to remain comfortable to lower temperatures extending the range by as much as 15 degrees.
Weight
Most good sleeping bags will include a weight on them. This is how much the bag weighs when in its stuff stack or rolled up. For car camping this really isn't important. When backpacking though this rating can make a big difference. A lower quality material will be higher weight as will lower temperatures. Average is near 4 pounds but can go lower with better materials.
There are several key criteria that you need to look at when selecting the sleeping bag that is best suited for what you plan on doing. For example if the sleeping bag is going to be used for an indoor children's sleepover, it is a waste of money to get that nice synth mummy bag good to 15 below zero. As such, the use of the bag is the first critical criteria to look at.
Where do you plan on going camping or backpacking and what time of year?
If you are camping in a low elevation state park in the middle of summer then just about any sleeping bag is likely to be good unless you are in Glacier Bay. A rectangular bag rated at 45F is likely to be well suited for your use in the standard summer time state park setting. However if you are into more extreme camping or backpacking then you need to closely study what you are buying. If you are planning on going above the snowline, a good sleeping bag can mean the difference between a comfortable night sleep and never waking up. It is best to lookup the historical temperatures for the area you are going (if there are any) as well as watching the weather reports for what the are is going to be like. Take the worst case cold temperature for the area and go a step below it for the temperature rating.
If you are only planning on backpacking during the summer months when it is comparably warm, there is a line of sleeping bags offered that are good to 45F and compress down to the size of a soda can. These are great for temperate areas when it is warm out. They are highly compact, weigh less than a pound, and they do the job nicely. Only concern is losing it in depths of you your backpack!