Perhaps the greatest backcountry danger is hypothermia. When you’re in the mountains you’re always a misstep, slip, or unexpected storm away from getting wet, then cold, then possibly hypothermic. This is why a sleeping bag is the most important piece of gear you take with you into the backcountry.
A good sleeping bag is your hypothermia safety net. When all else fails zip up in your bag and wait it out until you’re warm and dry. When you’re in the backcountry, you want to go with the best sleeping bag you can afford while minimizing the weight you carry.
The most important factors to consider when choosing a sleeping bag for backpacking are weight and warmth. Sleeping bag cost and weight are primarily determined by the sleeping bag’s temperature rating and fill material. Bags with lower temperature ratings weigh more. Down bags have a higher warmth to weight ratio, but cost more and don’t insulate when wet. Synthetic bags insulate when wet but are heavier. This article will help you consider your sleeping bag options based on your budget and activity.
Determine your Sleeping Bag Temperature Rating
Temperature rating is the most important feature to consider for your backcountry sleeping bag. I have written a guide to help you determine which temperature rating is right for you. This guide includes maps of low temperature by season, so you can determine the temperature rating you need based on the places you visit most.
It is important to select a temperature rating that will keep you warm during your seasons of use. However, you don’t want to overdo the warmth or you will be uncomfortable at night. Warmer bags are also heavier so you may be carrying around weight you don’t need. I’ve found that a 20 °F sleeping bag is a good temperature for me to use in the mountains from late summer through early fall.
In addition to my temperature selection guide, you may also want to learn about how sleeping bag temperature ratings are determined. Each sleeping bag will have different temperature ratings that will help you understand which rating best describes your personal warmth level.
Decide on a Fill Material
Sleeping bag insulation is composed of either down or synthetic material. Down is soft under feathers of birds, and makes excellent insulation. Synthetic insulation is man-made. Each has it benefits and shortcomings.
The best feature of down is that it has a very high warmth-to-weight ratio. What that means, is if you take the temperature rating of a sleeping bag and divide it by its weight down insulation will give you a higher number than synthetic insulation. The warmth-to-weight ratio is a way of standardizing across different sleeping bags and fill materials for sleeping bags of the same temperature rating.
In a nutshell, with down, you can get a very warm sleeping bag that doesn’t weigh very much. It’s easy to find down sleeping bags with temperature ratings around 0 °F that weigh 3 to 3.5 pounds. A 20 °F down bag will probably be about a pound less, in the 2 to 2.5-pound range.
While down is very warm and light, it does have two downsides. It’s expensive and doesn’t insulate if it gets wet.
A down bag is probably going to cost at least $100 more than a comparable sleeping bag with synthetic insulation. The price difference can be much higher. A budget down bag (ISO or EN rated, of course) is probably going to come at a price point between $150 and $300, depending on the temperature rating. Sleeping bags with a temperature rating of 30 °F and higher will probably come in a little lower. It’s common for down bags to cost over $500.
More importantly, is the inability of down to insulate once it becomes wet. If you get a down bag you’ll need to go to every effort to make sure it stays dry. Many bags will have some features that help prevent the down from getting wet, even in soggy conditions. Some down insulation is treated with a water repellent coating. From what I’ve read, these treatments work well as long as the down is not compressed (like when you’re laying on it).
Other manufacturers make the outer sleeping bag material water-resistant so that water can’t penetrate the insulation inside. The downside to this is that most waterproof materials aren’t the most comfortable.
Another thing to consider is that if your down bag is for very cold conditions, most of the water you encounter will probably be frozen. Thus, it will be hard to get your bag wet in the first place.
Down bags are very warm, and it’s nice to cut the weight when you’re backpacking. Just know the potential pitfall of losing insulation if your bag gets wet and take the proper precautions to prevent it.
Sleeping bags with synthetic insulation are going to cost much less than those with down insulation. It’s easy to find ISO or EN rated synthetic sleeping bags for under $100. Most synthetic fills also provide good insulation even when they are wet. This can be important if you’re worried about an unexpected storm or frequently visit wet areas. The primary downside to synthetic insulation is the weight.
A synthetic sleeping bag is going to weigh about 50-75% more than a down sleeping bag. The weight difference becomes especially apparent for warmer bags (those with temperature ratings below about 20 °F). It’s still easy to find a 20 °F synthetic sleeping bag that weighs under 3 pounds. However, it’s quite difficult to find a 0 °F synthetic bag that weighs much less than 4 pounds.
I nearly always buy synthetic bags. The biggest factor is the price. I can get a quality synthetic bag for half the cost of a down bag. When I’m in the backcountry I also like to play it safe. I’d rather carry the extra pound or so and know that if I take a spill in the river I’m not going to be in danger of hypothermia because my sleeping bag is wet. It’s one less thing I have to worry about going wrong.
Consider Your Activities and Budget
In the end, the sleeping bag you get is going to largely be determined by what you do and how much you can afford to spend. If you’re a through hiker trying to cut every ounce possible to push out more miles each day, then you might want to invest in a down bag. Same for mountaineers that have to carry that weight up snowy, icy peaks.
My guess is that for most of you, a synthetic bag is going to do the trick. You can spend a little less money and have security in knowing that your bag can get wet and still keep you safe.
If you’re a beginner, I definitely recommend getting a synthetic bag. Don’t drop a lot of money on a down bag and then find out it’s not what you needed. Try an inexpensive synthetic bag first so you can learn what temperature rating works best for you and what other features you like, or don’t like.
Sleeping bags are great things. They give us confidence and safety in the backcountry. I hope this guide helps you determine which type of sleeping bag will best meet your outdoor needs.