The temperature specifications of the sleeping bag - this is what matters

 Two values ​​are particularly important: T_comf and T_lim

Here, using the example of DownWool Subzero:

1. The first value – T_comf – is the value at which freezing is just not occurring. This means that T_comf is the lowest value of the comfort range, here it can get quite cool.
2. The second value – T_lim – is the value at which you can start to feel cold, i.e. start to shiver.
3. The third value – T_ext – is a theoretical value at which there is already a risk of health damage due to hypothermia. You don't need to consider this value when purchasing a sleeping bag.

According to EN 23537-1, precise temperature specifications for children’s sleeping bags not permissible! The reason for this is that children vary so much in their development that, for example, even two children of 140 cm height cannot be compared in their temperature sensitivity.

Uniform testing procedure

  Sleeping bag temperature test dummy Karel (Image source: TZU Textile Testing Institute)

To guarantee neutral comparability of the temperature ratings of sleeping bags, these are determined in a laboratory procedure according to the European standard EN ISO 23537-1 using a uniform test procedure:

A heated manikin lies in a test sleeping bag in an air-conditioned room. The energy input required to maintain a stable temperature of approximately 20 different body segments is then determined.

Reality check of the temperature value according to standard

Grüezi bag® considers this test procedure insufficient: EN ISO 23537-1 measures sleeping bags under precisely reproducible laboratory conditions. 
This allows for objective product comparison – but nobody sleeps in a laboratory.

• A standard doll is not comparable to an average human: it is standardized to the age of 25 years, she doesn't move in her sleep, does not pull the feet up, only sleeps on your back instead of on your side.
• The measuring points are on the top of the doll, not on the back, for example.
• In addition, the word "comfort temperature" is misleading: T_comf is the lowest value at which people who are normally sensitive to cold and in good health do not feel cold.
• Personal perception of cold is influenced by, among other things:
  • individual constitution and metabolism
  • Nutrition, exhaustion and daily form
  • Sleeping mat, clothing and tent
  • Wind, moisture and subsoil

Therefore, we understand the standard values ​​as technical basis for comparison, not as a guarantee of comfort in every situation. We therefore recommend the specified The comfort range should not be undercut..
People sensitive to cold should plan for additional safety margins.

Please allow for a buffer if you generally get cold more easily or are on physically demanding tours and might be exhausted by the evening. Even if the altitude is unusual or the local conditions are less hygienic, your body will perform better and require more energy. All of this makes you more sensitive to the cold.

Realistic temperature information for Grüezi bag® sleeping bags

We want happy customers who don't get cold. Therefore, please note:

• In addition to the EN-ISO standard, we also provide our recommendation for the optimal temperature operating range.
• When comparing sleeping bags, it's essential to always look at the same dimensions (length, width, and down fill). Only then can you accurately assess the quality and weight of a sleeping bag. For example, if the back panel is sparsely filled while the top is heavily filled, the sleeping bag might achieve a good temperature rating in tests, but not in real-world conditions. When you move around in the sleeping bag during the night, your back will be cold due to the lower fill, and heat will escape. Therefore, a Grüezi bag® DownWool® sleeping bag has the same fill level on both the top and bottom. Any perceived difference arises solely from the varying baffle sizes.
• A Grüezi bag® sleeping bag has a comfort cut: real people sleep more soundly when they don't feel like they're scrunched up in their sleeping bag and can even pull their knees up. That's why we cut our sleeping bags a little wider and even offer additional versions for people with a broader build. Because if your shoulders are pressed tightly against the sleeping bag, you'll have a cold spot due to compressed insulation and less air circulation.
• Important: Contrary to popular belief, a tighter sleeping bag is not warmer. It warms up faster because there's less air inside to warm. But air also insulates, so looser models are more insulating. If you want more comfort (more room) with the right body size, you can of course go for the larger version. You'll just have to warm up more air.
• We have a Heating part for the sleeping bag Developed for this purpose. Since a sleeping bag itself doesn't heat, but only reflects body heat, you may find yourself exhausted and colder than usual after a long hike. The heating element can preheat the footwell for 10 minutes, and the sleeping bag retains the warmth throughout the night. This heating element is included in all Grüezi bag® DownWool hybrid mummy sleeping bags and feater integrated or can be retrofitted in the “DownWool-Hybrid Ice Alpine”.
• We use high-quality RDS-certified down, which provides unique insulation. The ratio of down to small/support feathers is 90% down and 10% small feathers. They also have a high-quality bulk (at least 700+). cuin, for the extra-warm DownWool hybrid sleeping bags, even goose down with a fill power of at least 800+. cuin). 

Our tips and experience on the temperature range of sleeping bags