Temperature Ratings Explained
ISO 23537 is the common sleeping bag testing standard adopted and strictly enforced in the US since 2017 (Previously known as EN13537), so we decided to test our products according to the toughest standard in existence.
Ratings are based on a person wearing one long underwear layer and a beanie, sleeping on an insulated surface. If you wear multiple layers while sleeping, you might feel comfortable in colder temperatures than the advertised temperature ratings. However, everyone's body and sleep comfort differs, and conditions of use greatly affect total insulation: your posture, clothing, sleeping pad R-value, wind, humidity, etc.
Please also keep in mind that ISO 23537 ratings are ratings for a person sleeping. A person's body temperature drops while sleeping and increases while being active. If you wear your Selk'bag while being active, you will feel comfortable in lower temperatures than the advertised temperature ratings.
Here is a brief definition of the different temperature ratings:
Comfort: the temperature at which a standard woman or "cold sleeper" wearing the Selk'bag can expect to sleep comfortably in a relaxed position.
Limit: the lowest temperature at which a standard man or "warm sleeper" wearing the Selk'bag can expect to sleep comfortably in a relaxed position.
Extreme: the temperature at which a person wearing the Selk'bag can survive for six hours without risk of hypothermia or death. We do not advertise or recommend this temperature rating since it is a survival rating and a sleeping bag should only be used in this temperature as a last resort or emergency.
ISO ratings are intended as a guideline only, to help you compare sleeping bags, rather than a guarantee of warmth.
If you would like to learn more, our partner REI has made a great video explaining temperature ratings. Check it out here
