How to Interpret A Sleeping Bag’s Temperature Rating
Question: How are sleeping bags rated and what does the rating mean?
Almost all sleeping bags have a temperature rating. Often, the temperature provided, is totally random. On one of my trips to China, I viewed the final packaging of sleeping bags at one of the factories. What I saw bothered me; the finished bags were coming down a long assembly line. At the terminus were five fingers, of which three were in use. These identical sleeping bags were being boxed; one box stated 20 degrees Fahrenheit, the second 30 degrees, and the third stated 40 degrees. The true temperature rating is measured by a calibration in the European Union (EU). Even with this “certified” rating, a lot of variables come into play. There are three EU Certifications; comfort, standard, and survival; almost all certified bags utilize the survival rating.
A survival rating is based on the occupant not getting frost bite. The following parameters are used in this calculation:
1. The occupant has consumed the average number of calories required to support the physical exertion of the day.
2. The sleeping bag is insulated from any ground influence; i.e., a good insulation mat.
3. The sleeping bag is within a tent such that there is no wind / chill factor.
4. The sleeping bag thoroughly encapsulates the body heat such that there is minimal heat loss.
In a perfect setting, the resulting rating works; however, for a normal person’s comfort level, I recommend adding between 15 and 20 degrees to the EU Certification.
Jerry – The Gear Guy