"4) Montebell teeny tiny down parka reviewed by Marlin here on QJ saved my tush as I used it to sleep in when my 30 degree big agnes bag wasn't going to do much in 40 degree weather   

(who rates these things anyway?)"


the manufacturers  - there is a standard test   "EN Ratings" that a manufacturer can/may submit his product for - they use a standard setup with a copper dummy under standard conditions.  For bags that have undergone the testing and rating, you can have a very precise comparison between similar bags

Note that the dummy has on a base layer (i.e. something like polypro underwear) and I think it may have a wool hat on as well ? - typically, that is how most manufacturers rate thier bags anyway - they assume you will have your union suit and wool hat on and a suitable insulated sleeping pad -

for enlightenment - look at the Marmot website; they have thier bags tested and the ratings posted (and I think a link or explanation of the test).  you can probably also find info about the test in Wikipedia I'd guess.

I noticed an increase in the bag weights for Marmot bags once they started doing the EN testing - I assume they added some additioanl insulation to keep their X deg ratings - i.e., what they called a 30 deg bag needed a bit more fill to meet the test results for 30 deg classification.  For some manufacturers, they have thier bags tested, but haven't changed anything, so when you read the "fine print" of the test results, the so-called 30 deg bag    isn't   its maybe 33 or 35