Sleeping Bags
While it is always important to consider how you plan to use equipment, sleeping bags tend to be more of a general-purpose general purchase. However, if you are planning on serious winter camping (in very cold weather) or mountaineering, you may well want to invest in a winter bag that is rated to twenty or thirty degrees below zero, in addition to a lighter bag for three-season use. Alternatively, some bags offer zip-out linings, so you have a double bag for cold weather, and your choice of the lining or outer bag for warmer conditions.
In general, three-season bags are rated to about 20 degrees above zero, which will work for warm conditions and usually be sufficient for brisk spring and fall nights. However, remember that there is no universal standard for bag rating. Also, people sleep at different temperatures, so while a 20-degree bag might keep your companion warm on a cold night, you might freeze in the same bag.
When you buy a bag, a good rule of thumb is to think about the coldest condition you might experience, and then drop down ten or twenty degrees. Keep in mind that it is more difficult to stay warm in an insufficiently insulated bag than it is to vent a bag designed for cooler temperatures. A bag rated to zero is usually a good choice, since it will keep you warm on unexpectedly cold nights, but can be zipped open for venting.
When you buy a bag, any bag, there are several features you should check. Start at the top.
 What is what on a sleeping bag |
Draft collar. Scrutinize the draft collar, which is at the base of the hood. This insulated tube is designed to prevent heat loss from around your neck and shoulders. Rectangular, summer bags may not have draft collars, but they are an instrumental part of winter bags. The collar should be fluffy enough to fill the excess space between your neck and shoulders, but not so bulky you feel like you are wearing an inner tube around your neck.
Foot box. Since your feet take up room in the bottom of the bag, many sacks are designed with a flared, boxed, or barrel-shaped foot box to accommodate these protrusions better. In some mountaineering bags, extra room is added to the foot box to accommodate boots or water bottles.
Zipper and stitching. Look at the zipper and stitching. The zipper should have teeth big enough to run smoothly, without catching on fabric. Make sure the fabric has enough integrity to hold up along the sewn seams. Tug evenly at the seams to ensure that they don't separate from the fabric, and that the fabric stays in place. Stitching should be close and tight. Open the bag and look at the overall construction, features and finish of the bag to determine its quality.
Zipping bags together. One convenient trick is to zip two bags together to turn a single sleeper into a double. Many manufacturers use the same zippers. If bags have zippers that are similar in design, they can often be zipped together. If you are zipping two bags together, you can use bags of different warmths. In cold situations, put the thicker bag on top. Remember that mated bags provide less heat than separate bags, since there are more gaps and more movement to push out warm air. If you have a bag you might want to mate with your new purchase, bring it along to ensure compatibility.
Zipper flap. Most bags have an insulated tube or flap that runs parallel to the zipper in order to block heat loss. The tube should be sewn only to the lining material, since sewing through the bag creates holes that allow air leaks. Cold weather bags may have two thickly filled draft tubes. If there is a single flap or tube, it should be sewn to the top zipper so it hangs down when you sleep. Flaps or tubes that are too narrow may interfere with the zipper, so check out the action before you buy.
Pockets. Some bags come equipped with accessory pockets, but they can be more of a hindrance than a help. Are you a Princess and the Pea sleeper? Do you really want to roll over onto your glasses and car keys? If an accessory pocket sounds appealing, put items in it to test its position and padding.