Hittade det här på den siten du länkade till (lysande site btw, tack, ger mycket mer info än den polska ).
Technical Note - temperature ratings and overall weight
1. The effectiveness of insulation materials is affected by moisture. You will feel colder in your sleeping bag in high humidity conditions. Moisture will also add to the weight of a sleeping bag.
2. How warm you feel is also dependent on where you are sleeping. The size of the body of air surrounding the sleeping bag and the amount of air movement/ventilation both affect heat retention.
The comfort temperatures that we quote for Cumulus sleeping bags assume that they are being used in average humidity conditions inside typically-sized 1 to 3 person tents (with a relatively small body of still air surrounding the sleeping bag). Use them in a drafty, unheated mountain hut in damp conditions and you will feel significantly colder.
That said, independent tests, carried out on our models in compliance with British Standard BS4745 and ISO 5087-1, gave temperature performance figures that are as good as or better than we claim.
Technical Note - temperature ratings and overall weight
1. The effectiveness of insulation materials is affected by moisture. You will feel colder in your sleeping bag in high humidity conditions. Moisture will also add to the weight of a sleeping bag.
2. How warm you feel is also dependent on where you are sleeping. The size of the body of air surrounding the sleeping bag and the amount of air movement/ventilation both affect heat retention.
The comfort temperatures that we quote for Cumulus sleeping bags assume that they are being used in average humidity conditions inside typically-sized 1 to 3 person tents (with a relatively small body of still air surrounding the sleeping bag). Use them in a drafty, unheated mountain hut in damp conditions and you will feel significantly colder.
That said, independent tests, carried out on our models in compliance with British Standard BS4745 and ISO 5087-1, gave temperature performance figures that are as good as or better than we claim.