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

To guarantee neutral comparability of the temperature ratings of sleeping bags, these are determined 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.

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

Reality check of the temperature value according to standard

Grüezi bag considers this testing procedure to be insufficient: 

• 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. 

The value at comfort temperature is therefore only suitable for people who are young, healthy and fit.

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 specifications 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, always look at the same dimensions (length and width, as well as the amount of down). This is the only way to determine how good or heavy a sleeping bag is. If, for example, the back section is lightly filled and only the top section is heavily filled, then the sleeping bag will have a good temperature rating in the test, but not in real life. When you turn over at night in the sleeping bag, your back will be cold with the lower fill level, and the heat will escape during the night. Therefore, a Grüezi bag sleeping bag is filled equally on both the top and bottom. Any perceived difference only arises due to the different chamber sizes.
• A Grüezi bag sleeping bag has a comfort cut: real people sleep more soundly when they don't feel like they're in a sausage skin and can tuck their knees in. That's why we tailor our sleeping bags wider and even offer wide versions for people with a broader build. Because if your shoulders are snug in the sleeping bag, you'll experience a cold bridge due to the compressed insulation and less air insulation.
• 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