Many – but not all – sleeping bags comply with the EN13537 test (updated in recent years to ISO 23537-1:2016), a European standard for sleeping bag temperature ratings. We only supply bags that have been EN13537/ISO 23537-1:2016 rated.
An EN13537 rating gives a temperature range that a typical user can use as a guide for the conditions in which their bag will be most effective. Because women generally sleep colder than men, the ‘typical’ user is defined as a woman.
The standard measures three temperature ratings:
Comfort is the temperature at which a woman can expect to sleep comfortably, without feeling cold, and in a relaxed position (not curled up).
Lower Limit is the temperature at which a man – by definition warmer – in a curled position will start to feel cold, but not to the point of shivering. This is the limit of performance for the sleeping bag.
Extreme is the temperature anyone can expect to feel particularly cold and there is a risk of hypothermia. You should only use the sleeping bag in this range in an emergency.
Just so you know: the EN/ISO temperature test uses a thermal mannequin – a humanoid test-dummy with temperature sensors and an internal heating system – which is dressed in a clothing layer producing a consistent, minimal thermal value. The mannequin is out into the sleeping bag and both are placed inside a sealed climate chamber, on top of a timber plank. The mannequin is then heated to simulate body warmth, while also being subjected to various air temperatures inside the climate chamber. Sensors on the mannequin’s skin surface are able to trace and record the surrounding temperature including the insulation/thermal resistance value of the test sleeping bag.