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1. Down or synthetic fibre?

Find out which sleeping bag is suitable for what occasion

you can find out in this product comparison overview!

Am I likely to be outside, even when it’s raining cats and dogs? Is my destination warm and damp, cold and wet, or hot and dry? Will I be carrying my sleeping bag? Will I look after it properly? These are all questions that help when deciding on down or synthetic fibre.

Down sleeping bags


  • Unique heat-weight ratio
  • Small pack size
  • First-class moisture transport
  • Very durable if properly maintained
  • Warms immediately


  • Useless when wet
  • Requires extensive care
  • Attracts moisture
  • Dries very slowly

If very good insulation values are required with the lowest possible weight and compact dimensions, a down sleeping bag is the best choice. Synthetic fibre does not achieve the same loft capability as this natural product, which is thus able to store warm air perfectly.

When cared for correctly, down is also more durable than synthetic fibre. It also provides a pleasantly dry sleep climate. This is based on its capacity to absorb and release moisture. However, its moisture absorption is limited. In the case of extremely high humidity, continuous rain, or proximity to bodies of water, down can clump, which reduces its insulating effect. Once the down is wet, it takes a very long time to dry out.

This is a disadvantage on multi-day winter tours. The moisture of the body condenses in the filling, freezes there and can no longer dry off. Even in a bivouac sack, a part of the sleeping bag will freeze. A waterproof sleeping bag liner helps the down, but reduces the sleep comfort typically enjoyed with down products.

Areas of use: Mountain climbing, trekking in areas with low to normal air humidity, bike tours with lightweight luggage.

Here is a small selection of our down sleeping bags:
Astro 250
Astro Pro 400 SL
Astro Pro 600 SL
Astro Pro 1000 L

Synthetic sleeping bags


  • Still insulate at 70% even when damp
  • Easy-care 
  • Hardly absorb any moisture
  • Quick-drying


  • Heavier than down
  • Less compressible
  • Less moisture transport
  • Shorter lifespan than down
  • Somewhat longer warm-up time


Their disadvantage is also their great advantage: They hardly absorb any moisture and dry much faster than down sleeping bags. Even if they do get damp, they still keep you warm. The hollow polyester fibres continue to store warm air, since they remain stable and don’t clump like damp down does. Also ideal for use in areas with permanently high humidity. If extremely low temperatures are not expected, or the sleeping bag experiences heavy use and regular washing (children!), synthetic sleeping bags are the right choice. Ultimately, they are less expensive than down models and easier to care for.

Areas of use: All-round sleeping bags, canoe tours, winter tours, wilderness in Scandinavia, bike tours with lightweight luggage, hut tours, summer sleeping bag.

Here is a small selection of our synthetic sleeping bags:
Exosphere -10°
Exosphere 0°
Orbit -5°
Orbit SQ +5°

2. Which sleeping bag for which temperature?

Temperature indications according to EN 13537

How is it measured: A calibrated, thermal, articulated “adult” dummy is put inside the test sleeping bag, which is then placed in a climate chamber with a standardised environment. As the horizontal areas of the doll are subjected to specific heat output, sensors measure the temperature difference between the internal and external surface over several hours. The respective temperature range is calculated from the results. This way, EN 13537 creates a comparable standard that serves as a basic orientation.

These standardised indications only provide laboratory values. They are designed to ensure good comparability among the products of various manufacturers. Since each body is individually structured and responds individually to the given circumstances, this information can only serve as an indication for a purchasing decision.

Factors to take into consideration:

  1. people have more heat-determining factors than an “articulated dummy” in the climate chamber. For example, temperature levels differ between men and women, and according to age, condition, but also experience. Thermal output is also affected by the degree of exhaustion (tired or rested), but also if you have eaten too little or drank too much alcohol (the body loses heat faster under the influence of alcohol).
  2. External circumstances that are “standardised” in the climate chamber play an important role in reality and contribute to the optimal use of the “thermal output”.
    1. A good sleeping base insulates the sleeper from the ground.
    2. Functional underwear that is dry and can emit moisture to the outside (hat!). - Protected sleeping area, as wind and moisture significantly impair restful sleep.
  3. The standardised measured values are determined in the climate chamber, i.e. directly from everyday life. Please bear in mind that multi-day activities or difficult natural conditions have completely different requirements and it is therefore necessary to prepare for the relevant circumstances.

Temperature ranges

  • T(COM): Comfort

indicates the lower temperature limit at which an average woman (25 years / 60 kg / 1.60 m) can comfortably sleep through one night.
In this range, the inexperienced user feels comfortable at all times.

  • T(LIM): The Lower Limit

specifies the lower temperature limit at which an average man (25 years / 70 kg / 1.73 m) can comfortably sleep through one night.
In order to remain warm in this range, the user must adapt their clothes and behaviour to suit the circumstances.

  • T(EXT): Extreme

indicates the lower extreme temperature that an average woman can withstand in extreme cold for 6 hours. There’s no chance of sleeping here. In the extreme range, you can expect to feel very cold. Hypothermia poses a risk to health.

3. How do I use my sleeping bag correctly?

For a warm and restful night’s sleep in your sleeping bag

However, the right sleeping bag is only part of it – it’s also important where, how and on what you sleep!

  • Sleeping mat: a cold floor or circulating air extracts heat from the body even through the best sleeping bag! Prevent this heat loss (A) by using a good insulating mat.
  • Wind protection: wind can make you feel very cold! Due to the chill factor, the body perceives +5°C in a light breeze (25 km/h) as 0°C. A tent, bivouac sack or even a boulder can protect against a strongly chilling air exchange (B). The sleeping area should, therefore, be in a wind-protected location.
  • Functional clothing: the warmth of a sleeping bag can be increased quite simply by wearing warm and long functional underwear and socks. Dry clothing on the feet also ensures additional insulation.
  • Hat: in your sleeping bag, your head or face are the only contact to the chilly outside world. A cold head makes the rest of the body lose heat too. A hat, perhaps even a balaclava, offers very effective protection against the cold.

A sleeping bag cannot generate heat – it can only retain the existing heat!

  • Enough food: the body needs lots of energy when climbing, hiking, cycling, etc. Athletes who do not fill their energy reserves with sufficient food cannot produce enough heat and therefore get cold faster.
  • Drink plenty: drink enough throughout the day, because a dehydrated body can no longer produce enough heat. Before getting into your sleeping bag, a hot chocolate or tea warms you up well.
  • Avoid alcohol: avoid excessive alcohol consumption at cold temperatures. Alcohol initially gives off a warming sensation, but when it diminishes, you feel the cold even more.
  • Keep things dry: clothing and sleeping bags, especially down ones, have a lower insulation value when they’re wet than they do when dry. The supposedly warm socks that you were wearing get cold very quickly due to evaporation. Avoid getting into your sleeping bag with your sweaty clothing on. A change of clothes will stay dry in a watertight packsack. And whenever possible, put the sleeping bag to air – for example, on the tent.