Temperature Ratings

Temperature Rating System

When buying a sleeping bag, the so-called " temperature range or value" is very important. This is determined according to the European standard EN 23537 using a standardized test procedure. It provides the most important orientation values, which are usually shown in three temperature values.

  • Comfort Limit: is the lowest value of the comfort range, where it can already get cold.

  • Sleeping Limit: is the value at which you can start to feel cold, i.e. you can start to shiver.

  • Risk Range: is a theoretical value at which there is a risk of hypothermia.

According to EN 23537-1, precise temperature specifications for children's sleeping bags are not permitted! The reason for this is that children differ so much in their development that, for example, not even two children of 140 cm height can be compared in their temperature perception.

Testing Procedure

In order to guarantee neutral comparability of the temperature specifications of sleeping bags, the temperature ratings are determined according to the European standard EN 13537/EN 23537 using a uniform test procedure:

To perform this test, a heated manikin is put in a sleeping bag in an air-conditioned room. The amount of energy required to keep the temperature of the approximately 20 different body segments stable is then determined.

Testing Limitations

Whilst this testing is extremely useful there are some limitations associated with this testing, as follows:

  • A standard doll cannot be compared to an average human: it is standardized to the age of 25, it does not move in its sleep , does not pull up its feet, and only sleeps on its back instead of on its 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 because the specified comfort temperature indicates the lowest part of the comfort range, i.e. the temperature at which it becomes cool and a person feels cold.

Gruezi Bag’s approach to determining the optimal temperature range

At Gruezi Bag we are very cautious with the temperature information on our sleeping bags and add a buffer to the limits determined from the laboratory. For example, in the laboratory the Biopod DownWool Subzero reaches -2 °C however, we specify +2 °C. This helps account for variability in conditions and personal preference.

Please note when comparing sleeping bags:

  • Length, width and the amount of down are all extremely important. Some brands use a lower amount of down on the bottom of the sleeping bag. Whilst this can lower the weight, this can lead to heat loss or cold spots, especially if you turn over at night. This is why Grüezi bag sleeping bags are filled the same on the top and bottom.

  • A Grüezi Bag sleeping bag has a comfort cut: real people sleep more peacefully when they don't feel trapped and can move their legs. That's why we tailor our sleeping bags wider and offer even have wider versions for people with a broad stature. Because if your shoulders are snug in the sleeping bag, you have a cold bridge there due to compressed insulation and less air insulation. Contrary to popular belief, a tight sleeping bag is not warmer. It warms up faster because there is less air inside that needs to be warmed up, but air also insulates, so the looser models are also more insulating. There is also a higher chance of cold spots in tight sleeping bags due to the insultation being compressed.

  • We use high-quality RDS-certified down, which offers unique insulation. The  down to small/support feather mix ratio is 90% down and 10% small feathers.  They also have a high fill power (at least 700+ cuin, and for the extra-warm DownWool hybrid sleeping bags even goose down with at least 800+ cuin). 

  • A sleeping bag can only reflect body heat. If you are exhausted or colder than normal after a long tour, you will have less body heat to warm the sleeping bag. To assist with this, Grüezi Bag has developed a heating element that can be used to preheat the sleeping bag and keep you warm and cosy all night long. This comes as an add on that can be secured into your sleeping bag, and has been integrated into our expedition models as standard. All you need is a power bank