Just watch for what the rating is! A lot of American manufacturers have not adopted the European EN 13537 rating system, and their ratings therefore range from somewhat accurate to purely fictional. The EN13537 system has several different ratings, and there is a lot of difference (at least 20* C) between the "Comfort" and "Extreme" ratings. On American bags where the ENetc. rating is given, I've so far noticed only one rating listed, and the manufacturer seldom states which one it is!
Here is an explanation (page down to "How to Understand...": • The EN 13537 Upper Limit or Maximum Temperature is the highest temperature at which a ‘standard’ adult male is able to have a comfortable night’s sleep without excess sweating.
• The EN 13537 Comfort rating is based on a ‘standard’ woman having a comfortable night’s sleep.
• The EN 13537 Lower Limit is based on the lowest temperature at which as ‘standard’ adult male is deemed to be able to have a comfortable night’s sleep.
• The EN13537 Extreme rating is a survival only rating for a ‘standard’ adult woman. “In the risk range a strong sensation of cold has to be expected and there is a risk of health damage due to hypothermia.” This is an extreme survival rating only and it is not advisable for consumers to rely on this rating for general use. The best guideline temperatures for purchase decisions are the TComfort and TLimit ratings.
There have been some problems with the testing for these ratings, and they're not always that reliable. Most of us are not mannikins!
Here's an example. In addition,
anyone buying a 20 degree bag will be surprised when they learn that they have to sleep on a 1.5 inch pad, wear long underwear, socks, and a hat to achieve the temperature rating that they thought the bag was rated for.
I personally would want a bag that was at least 5 degrees F warmer than the "Comfort" rating! And I normally sleep in long underwear, socks and a hat!
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