- Mummy – tight-fitting and contouring your body shape, these bags offer the most lightweight shape, since they are smaller overall. They achieve warmth by limiting the volume of space around your body that needs to be heated throughout the night. Their light weight and smaller size make them the best option for backpacking, as long as you’re ok with less room to spread out at night.
- Semi-Rectangular – these are slightly roomier than mummy bags (imagine a crossover between a mummy bag and a rectangular bag), so they’re great for people who don’t mind adding a little weight for a more spacious and comfortable night’s sleep. These bags are great for rafting or basecamp hiking trips where weight and compressibility aren’t as critical.
- Rectangular – the comfort-driven shape of sleeping bags, these are great for car camping, where you’re not carrying the bag more than a few yards from the car. Enveloping lots of space around your body with their rectangular shape, these sleeping bags are often thicker and heavier (to keep the same temperature rating as a mummy bag) because of the extra volume and insulation – and your body has more air inside the sleeping bag to keep warm! But the joys of being able to spread out (hopefully on a nice thick car camping sleeping pad) outweigh the bulkiness and weight of the sleeping bag.
- Down – known for its light weight and high compressibility, down insulation is great under cold but dry conditions. Look for a bag with high “fill power” – down that has a high loft – for better warmth, but be sure to take extra care to keep your sleeping bag dry. Down loses its insulating capability when it gets wet, so down sleeping bags require a little more maintenance and protection in the field.
- Synthetic – known to be heavier than down, but still insulating when wet, synthetic is very durable and often at a lower price point. It’s great for people with allergies – who may find themselves allergic to a down sleeping bag. It’s also a lower-stress bag in the field, as you don’t have to be quite as committed to keeping it perfectly dry.
- Summer – typically for temperatures 30F and higher, these bags should cover summer backpacking throughout the Lower 48. They’re lighter weight (because they have less insulation) and often can pack down smaller. Unless you sleep VERY warm, these won’t provide quite enough warmth for summer backpacking in Alaska.
- 3-Season – for midrange temps (15F to 30F), these bags are slightly heavier and more insulated. This is a good rating for a summer backpacking trip in the Wrangells – just be sure to combine it with a good sleeping pad if you’ll be sleeping on a glacier.
- Winter – for our spring/summer mountaineering trips as well as winter backpacking trips, these are the warmest bags, covering temperatures down to 15F and lower. They’re often quite tight-fitting (to limit the amount of interstitial space), and can be much bulkier and heavier than a summer sleeping bag (but well worth it when you’re sleeping on snow!) These can be overkill for a summer Alaska backpacking trip – leave it behind and use a 3-Season bag instead.
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