Next generation sleeping bags are attempting to boost comfort while shedding weight by ditching the traditional mummy design for something more akin to your bed at home.
What's The Matter With Mummies? Well, nothing really. They're an effective, efficient solution for packing you into as much insulation as possible with minimal weight and volume. But, some people find them to be claustrophobic and, in many situations, the all-encompassing insulation is actually unnecessary. When you're laying down, you compress the down, primaloft or whatever under you, minimising its ability to retain heat. When that happens, it's actually your sleeping pad keeping you warm, not the bag. So, why lug all that extra material along with you?
Comforters: Imagine a sleeping bag without a back. That's the idea with backpacking comforters — they're built just like sleeping bags, out of lightweight nylon and either down or a man-made insulation material — but, rather than a back, you simply lay them over your sleeping pad. Comforters tend to have some sort of connection to keep that sleeping pad in place and keep out drafts. Without that back, they're free to be smaller in packed volume and lighter than their all-encompassing counterparts.
We've spent a few nights sleeping in a Nemo Tango Duo Slim 30 comforter. Rated to -1C, the girlfriend and I have slept under it down to about -4C, at which point I was still so hot I was sweating, while she swore she was going to freeze to death. Two standard 20-inch wide sleeping pads fit in sleeves at the foot of the comforter, while two tie-off points on each side allow you to secure the pads together and wrap the comforter around their edges with paracord or anything similar. The detachable hood also wraps the pads and adds some valuable warmth for your head.
The real limitation with it isn't the warmth — absolutely on-par with bags rated to the same temperature — but in the cuddleability of using two sleeping pads. While spoonage is much sweeter using this system over two separate sleeping bags — the system it's intended to replace — the crack between the pads keeps both users in the middle of their own, not as good as one of the big, heavy pump-up air mattresses you'd use for car camping, which the Tango isn't compatible with.
The real advantage? Space and weight. The Tango packs appreciably smaller than my typical one-person Kelty Cosmic Down 20 mummy bag and weighs 57g less. Considering it eliminates the need for a second bag, that's significant.
Backcountry Beds: This innovative new bag from Sierra Designs is more along the lines of a traditional mummy, surrounding you entirely with insulation. Where it differs is in ditching the zipper for a shoe-style opening and tounge. The advantages of those are in facilitating a more traditional, bed-style of sleep where you can more easily roll over, open the bag, sleep on your side, whatever.
The cleverness of the Backcountry Bed doesn't end there. It also incorporates a sleeve sized for standard sleeping pads on the back, keeping your bag/pad together as you move around throughout the night. There's also a slit in the foot of the bag, allowing you to stick your feet out on warm nights and little mittens on the "tongue" so you can keep your hands warm on cold nights.
In British Columbia, I spend several below-freezing nights in the Backcountry Bed 600, rated to -3C, and can report that it really does offer significant comfort advantages over a traditional mummy, while retaining all of that design's warmth; the -3C rating feels conservative. Side sleeping, rolling down the tongue, rolling over, whatever, it all takes place seamlessly, meaning you do all that while staying asleep.
The disadvantage is packed size and weight. Sierra Designs is a higher-end brand, but this BackCountry Bed packs about 50 per cent larger than that less-expensive Kelty also referenced above while weighing about the same. Ultralight types are still better served by traditional bags.
Hybrid Bag/Pads: Enter the $800(!) Eddie Bauer First Ascent Airbender 20. It looks like a traditional mummy bag, but like a comforter, ditches the insulation on the back. That's because its inflatable, insulated sleeping pad is sewn right in. Its made from a higher fill-power down than either the Backcountry Bed or that Kelty mummy bag we're using as a reference, but weighs only a few grams more. That's incredible, when you consider it includes the pad (my typical pad, a Therm-A-Rest NeoAir All-Season, weighs 540g). And, you can likely ditch some of that weight by losing the included — and reportedly unnecessary — hand pump.
That high price is accounted for by the need to manage production of the bag across two separate factories and the new methods involved in constructing it. Like all new technologies, expect to see it drop radically as production is streamlined and volumes increase.
Sierra Designs also has a "garment style" bag called the Mobile Mummy that wraps your head tightly and incorporates ports for both your hands and feet, meaning you can wear it around your campsite, as well as inside your tent.
What These Bags Mean For You: Should you switch? If you're happy with your current mummy bag and sleeping pad, don't bother. If you're shopping and you're looking for the lightest weight, warmest insulation and lowest cost, don't bother. The real takeaway here is that there's now real options in the sleeping bag market, ones capable of significantly boosting comfort or dropping weight or, in the case of comforters, doing both, but only in a specific circumstance. People who want to cuddle, people who don't sleep comfortably in the confines of a mummy bag or high-end gear whores are currently the real winners, but we'll all hopefully be benefiting from this shake up of the outside-sleeping category in the near future.