Most sleeping bags are designed for independent use. If you wish for a cozy night of sleeping in two, you may also consider mating the bags to form a “double-wide” sleeping bag. This design can be typically found on sleeping bags with a moderate temperature rating.

This is because zipping two sleeping bags together will reduce their efficiency. It will also compromise their ability to reach the advertised temperature rating. The reason – more gaps and more movement pushing the warm air out and allowing cold air to enter the bag. That’s for sleeping in two.

But, what about solo sleeping? Can you double up a sleeping bag?

If you use two identical bags, the inner bag is very likely to get compressed and with reduced insulation potential. Not to mention that carrying around an extra sleeping bag is unnecessary extra weight. While there are obvious drawbacks to doubling up your sleeping bag, it may work fine if you intend to use it occasionally.

In this guide, we cover the advantages and disadvantages of using double bags and more about ways to make most of your sleeping in a bag. But first, more about the different types of sleeping bags.

Types of Sleeping Bags

Simple rectangular bags are slowly becoming the relict of the past – one zip down the side and that’s about all. Yes, you can still find them, but there’s a variety of different types available. Their shape notwithstanding, all sleeping bags should provide warmth and comfort for outdoor sleepers.

This is why you need to choose the right sleeping bag. Suited to the temperature, your own needs, the season, and the location.

Two sleeping bags

Sleeping Bags by Shape

Rectangular Sleeping Bag

If you’re one of those who prioritize plenty of space and comfort, this traditional type is probably the right choice for you. This type provides lots of room for restless sleepers, unlike tapered sleeping bags. While they do provide extra space, rectangular sleeping bags have certain limits regarding insulation. Besides, they typically don’t have a hood to keep in the warm air.

Rectangular sleeping bags are a great choice for indoors and car camping. They are not expensive, come with a zip that is compatible with other sleeping bags, can be used as a quilt, and provide lots of foot space.

Barrel-Shaped Sleeping Bag

This type is perfect for those looking for the spaciousness of a rectangular sleeping bag and solid insulating properties. Barrel-shaped sleeping bags come with a tapered shoulder area and footbox to decrease some of the dead air in rectangular bags. Some of them have a hood to further boost their insulating properties.

Barrel-shaped sleeping bags are a good option for backpacking and car camping.  They come with a hood, tapered footbox, and shoulders and are rated for colder temperatures than rectangular bags.

Mummy Sleeping Bag

A good choice for colder conditions, these bags are contoured to the body. They have a highly tapered footbox and leg area. With more width through the hips and shoulders and additional shoulder tapering, along with a hood you can tighten with a drawcord.

Mummy sleeping bags will surely make you warm and cozy, and they’re also much lighter than rectangular and barrel-shaped sleeping bags. With less room for tossing and turning, they may not provide an adequate level of comfort for some people.

These bags are a good choice for camping and backpacking and camping. They’re lightweight/small pack size, have solid warmth to weight ratio, and come with a hood with drawcord

Double Sleeping Bag

Two-person sleeping bags are suited to two adults. If a single sleeping doesn’t provide enough space or you enjoy snuggling with your partner at night, double bags are the best choice. However, the loose fit of most of these bags typically lets excess cold air in, thereby reducing the effects of the combined body heat. This is why you need a double bag with a good hood.

Some two-person sleeping bags unzip completely to make two single bags, which makes them more versatile for solo sleeping. Double bags are a good choice for car camping and romantic getaways.

Quilt

A sleeping bag may not be the best solution to keep you warm for every occasion. It may be too heavy to carry or the temperature may be too high to need a full sleeping bag. This is when you may consider opting for a quilt.

Backpackers have been increasingly using quilts. The thing is that as long as you have a sleeping pad insulating you from below, you’ll be as warm with a quilt as in any other type of sleeping bag. Quilts are best suited to hammock camping, backpacking, and summer camping. They’re lightweight, highly packable, and have a good warmth-to-weight ratio.

Elephant’s Foot Sleeping Bag

The elephant’s foot is designed to be lightweight, which makes it a perfect choice for mountaineers and light backpacking. While the elephant’s foot is tapered and highly fitted like a mummy sleeping bag, it has no hood. Besides, it’s a bit shorter than other types of sleeping bags and requires you to wear an insulated jacket to keep your upper body warm.

These sleeping bags are highly packable and have a good warmth to weight ratio, but come with ¾ length zip or no zip.

Sleeping Bags by Temperature Rating

Once you make a decision regarding a sleeping bag’s shape, you need to think about the temperature rating. It means you should pick a sleeping bag that is best suited to your activity. But it also means that you should consider your priorities – bare survival or comfort, which is why you should also think about comfort rating.

  • Extreme rating – Associated with a considerable risk of frostbite and hypothermia, this is the lowest temperature at which an adult female can stay alive in a sleeping bag.
  • Comfort rating – refers to the temperature at which an adult female is likely to sleep comfortably.
  • Limit rating – refers to the temperature at which an adult male is likely to sleep comfortably.

Temperature-Based Types of Sleeping Bags

Most types of sleeping bags are classified in one of these three categories:

  • Summer – low-temperature limit 35ºF, high-temperature limit over 35ºF
  • 3 season – low-temperature limit 10ºF, high-temperature limit 35ºF
  • Winter – low-temperature limit under 10ºF, high-temperature limit 10ºF

Sleeping Bag Insulation

Now that you’ve understood the different types of sleeping bags based on their shape and temperature rating, you should also consider their insulation. Most sleeping bags in the market are either down or synthetic.

Down Sleeping Bag Insulation

This is the insulation of choice for mountaineers and those opting for lightweight backpacking, mostly due to the great warmth to weight ratio. Yet, there are limitations to its insulating properties when it gets wet. And it can also take a long time to dry out.

Down insulation may not be the first choice for snow and wet environments. However, recent advancements in the development of water repellent down provide both warmth and low weight in these environments, as well.

Down sleeping bag insulation is a long-lasting, compressible and lightweight option, but maybe a bit too expensive and not as warm when wet. Regardless of your preferences, you should opt for brands whose down gear is RDS (Responsible Down Standard) certified.

Synthetic Sleeping Bag Insulation

Synthetic sleeping bag insulation is usually made from polyester and works almost like down. Yet, it’s rather heavy and not quite compressible. This may make it less interesting for light backpackers, but unlike down insulation, it dries quickly and performs solidly when wet. It is also less expensive than down.

On the other hand, synthetic sleeping bag insulation is less compressible and a bit too heavy.

Doubling up a Sleeping Bag

There is an ongoing debate regarding how much you should wear under your sleeping bag or how many layers you actually need. Some argue that you can get enough warmth by wearing as little as possible. Others opt for pants, jackets, pants, and base layers as a necessary prerequisite to boosting warmth.

Both camps may be right and ultimately, it depends on your outdoor experience and in what season you typically camp. Many experts believe that there is no alternative to layering heavily in the cold, whether you’re inside or outside the bag. Basically, you need those warm layers to preserve the heat.

The key to staying warm and comfortable – or as much as possible – is adaptability. If you’re feeling cold/hot, you need to make a change. The layering style makes it easier to adjust the temperature inside the bag.

On the other hand, any number of layers may not be enough if you don’t have an adequate protective layer underneath. Your clothes and your sleeping bag will get compressed and you are highly likely to lose heat due to conduction through the ground.

But what about doubling up your sleeping bag?

Pros and Cons of Doubling up a Sleeping Bag

Even if weight is not an issue, most expert campers, backpackers, or mountaineers would recommend buying one sleeping bag for the intended purpose. Moreover, the rating on the bag is as accurate as it can be and leaves no room for guessing. It means that if you’re going out into the wilderness, you’d need one sleeping bag with the lowest possible temperature rating (or at least, the one you expect).

Generally, the basic warmth of a sleeping bag depends on the amount of loft the fill provides. The fill quality largely determines how much loft is necessary to provide a given warmth, in addition to construction.

Theoretically, it means that if you have a solid 20F down bag with 4-5″ of loft, putting one inside the other would have 8-10″ and give you ~ -10F (or maybe lower). This providing there’s no down compression resulting from stuffing one bag inside the other. Given that there’s hardly any chance this could happen, the actual performance would be rather lower.

While it may seem appealing to combine two bags, there are certain drawbacks to this idea.

  • Bag design allows the insulation to loft to its maximum, thereby creating “dead air” around your body. This dead air actually keeps you warm. If you stiff one bag inside another, it may compress the insulation of the inner bag and reduce its heat-retaining properties.
  • Using two bags may result in a rather heavy and fairly bulky sleeping bag, which may just be too much for you to handle.

CLO Unit

In terms of clothing insulation, there is the concept of the CLO, being the basic measure of thermal insulation – thermal properties of clothing. One of the most comprehensible explanations of CLO suggests that the thicker the insulation the greater the CLO value. Notably, the thicker the insulation is the greater the heat retention is going to be.

Namely, you need 5 CLOs to stay warm if sleeping at 20F (yet, this can vary between people). It means that if you double the bags and disregard both the air gap between the bags and any compression of the insulation, you can simply add the CLOs.

Basically, a bag with 10 CLOs will provide as much warmth as adequate clothing in combination with a bag with fewer CLOs. If sleeping in an extremely cold environment, this can all vary on the basis of how warm you sleep. And also whether you’re sleeping in a snow cave or a tent. You should also think about the bags compressing each other, thereby reducing their insulation properties.