Buying a sleeping bag is no easy task. Firstly, the range is huge and then there's the question of; down or synthetic? Which temperature range? Which details are a must? Our buyer's guide helps narrow the choice.

A good night’s sleep is always important, but especially while traveling in the outdoors – whether on a weekend backpacking trip or a month-long expedition. Only by getting enough rest can the body (and mind) regenerate after a long and physically challenging day. For this reason we have made sure every field of application is covered by our sleeping bag selection. As is the case with most high-quality gear, the perfect universal sleeping bag does not exist. However, there is a perfect sleeping bag for any given situation; use the following information to find out what the differences are, and which sleeping bag best suits your needs.

Down versus synthetic

In order to be able to retain heat, a sleeping bag has to capture air in its insulating filling. There two general filling choices: down feather and synthetic fibres. Both types of filling have their advantages and disadvantages.

The perfect way to enjoy the great outdoors is sleeping in a comfortable sleeping bag. | Photo: Mountain Equipment
The perfect way to enjoy the great outdoors is sleeping in a comfortable sleeping bag. | Photo: Mountain Equipment


Down sleeping bags

A quality down sleeping bag has a long life (with proper care) and features an optimum warmth-to-weight ratio and pack size. The climate inside the bag is great as well, since down absorbs moisture instead of causing it to accumulate on the outside like synthetic fibers do. For this reason, down sleeping bags need to be regularly aired out and dried after use.

In cases where high humidity prevents propper drying, the down filling begins to clump and lose its heat-retaining qualities. Drying a down sleeping bag also takes longer than synthetic alternatives.

TIP: Sleeping bag liners
A cotton or silk liner used inside a sleeping bag keeps it from getting dirty, can be easily and quickly washed, and makes the sleeping bag up to 5 degrees warmer.

Down quality varies from animal to animal and depends on the species and its living conditions. Geese that live in the north, i.e. in colder climates, have the densest and largest down feathers. Ducks from more temperate climatic regions are not naturally equipped with such warm feathers. Their down costs less, but sleeping bags using it are also not as warm.

Down fillings are always a combination of down and other feathers. The feathers provide stability for the filling through their relative stiffness, while the down fluffs up the filling and provides most of the insulation. The ratio of down feathers to other feathers is usually stated among the product details.

A ratio of 90/10 for example means: 90% down and 10% other feathers. The smaller the amount of down, the less loft the filling has, leading to a reduction in its insulating capacity. This ratio however does not say anything about the quality of the feathers and down feathers used for the filling.

Down sleeping bags need to be thoroughly aired! | Photo: Deuter / Tobias Meyer
Down sleeping bags need to be thoroughly aired! | Photo: Deuter / Tobias Meyer

Brands such as Carinthia and Exped are two examples of high-end down sleeping bag manufacturers.

One of the ways to gauge a sleeping bag filling’s quality is by the so-called “fill power” value. Fill power is described as a ratio of the down’s volume to its weight. To determine fill power, an ounce of the down filling is compressed in a cylinder for 24 hours. It is then allowed to expand, and the total volume is measured in cubic inches (cuin).

Affordable sleeping bag models have a fill power of up to 450 cuin, whereas high-quality models often have over 650 cuin. To prevent thermal bridges the down filling is kept in place by H-, V-, or trapezoid-shaped compartments.

Synthetic Sleeping Bags

The greatest advantage of synthetic sleeping bags is that they are not as sensitive to moisture – a great option for wet regions and humid climates that make drying a challenge. Synthetic fibres provide insulation even when wet, making them perfectly suited for such conditions.

When it comes their comfort and warmth-to-weight ratio (and pack size) however, synthetic sleeping bags are inferior to their down counterparts. Synthetic fillings are made out of polyester fibres. The surface treatment of these fibres is import for their loft and longevity. Each individual fibre is coated with silicone to prevent them from becoming entangled or breaking. The more elaborately this is done, the better the fibre’s quality is (and the higher the price). Overall, synthetic sleeping bags are cheaper than corresponding down versions, since the synthetic fibres are manufactured in layers and are easier to work with than down. Both single- and multi-layer constructions are used.

Sleeping Bag Compartment Structures

The insulating filling (down or synthetic fibre) of sleeping bags is kept in place by compartmentation to prevent thermal bridges. The shape and size of these compartments, along with the sewing method used, heavily influence a sleeping bag’s overall quality

In the simplest compartment structure the compartments are sewn together side by side. This construction is however only suited for summer sleeping bags, since there is no insulating material (and thus thermal bridges) at the seams.

Diagonal compartmentation: Similarly to a shingle roof, the overlapping compartments form a consistent insulating layer without thermal bridges. Because of obvious similarities, this type of compartmentation is sometimes also called shingle compartmentation. Diagonal compartmentation offers the same benefits as H-shaped compartments, but weighs slightly more because of the fabric overlap.

H-shaped compartmentation: H-shaped compartments are used in down sleeping bags. Here the shell and liner of the sleeping bag are seperated by crosspieces in the H-shaped comparmentation, which prevents thermal bridges. More compartments means that the down is better fixated, but the crosspieces doe not insulate as well as down and can cause unwanted thermal bridges as well. For this reason manufacturers are always looking for ways to effectively use as few compartments as possible. H-shaped compartment structure is the lightest and is used for light-weight sleeping bags (e.g. for backpacking).

V-shaped compartmentation: This type of compartmentation is costly to produce and relatively heavy. It fixates the filling extremely well, and is similarly high-quality as a trapezoid construction – which achieves the same performance at half the weight.

In a quality sleeping bag a good night's sleep in the open air is assured! | Photo: Thomas Rögner / Mountain Equipment
In a quality sleeping bag a good night’s sleep in the open air is assured! | Photo: Thomas Rögner / Mountain Equipment

Synthetic-fibre sleeping bag vs. Down sleeping bag: an quick overview

Down sleeping bag Synthetic sleeping bag
Pros Pros
+ light + warms even in wet conditions, such as during an overnight stay outdoors
+ better insulation properties than synthetic fiber,
That’s why down is used in extreme conditions
+ cheaper to buy
+ even in warmer temperatures a comfortable sleeping climate can be expected due to a high breathability + easy maintanance
Cons Cons
– sensitive to moisture – less vapor permeable than down
– loses its feathers over time -increased weight, larger pack size
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