IDFL do not take into account the moisture resistance, after all it's "only" a 2000 euro test/unite! James came to this conclusion by him self.
The IDFL test is done at +5C (41F) with a relative humidity of 40%. The thing about this is, that our sleeping bag line, starts out at the freezing point 0C (32F), and then drops down to -45C (49F), so one could argue, that it's senseless to test at +5 and with 40% humidity.
But there are several other interesting points in the EN 13537 test, that needs to be known to the users:
The first point is, that there are a difference in the surface of the dummy's, between the different labs. The IDFL test is done with a dummy of 1.67m2 with a weight of 20kg and with 35 sensors - zones. Other dummys are 1.48m2 with 20 sensors, and the test is done at -10c (14F). Skin temperature is 33c in the first case and 34c in the second.
From this one can draw the conclusion, that test results can not be compared between different labs.
The second point is, that there are no "policing", or control, with the claims published. Any body can claim what they want, and as they are not obliged to make documented proof, anybody can actually claim what ever they like.
And this is the reason why we publish the documented proof as a PDF on each page of sleeping bags on our site. You get the report, and have proof that it's done, but secondly you get a document that allows you to compare to other claims. If there are no control of the claims done, by the commission, then it's up to the users/consumers, to force documented proof out of manufacturers when ever a claim is made.
There are another point, that's interesting, and related to the above: As there are properly a deliberate mess between the labs, it's known that some labs offers better test results than others, and as ONE test is invoiced 2000Euros, it quickly becomes a "offer/demand" issue: you pay...you get.
Rumors even has it, that EN 13537 test are made in country's, where there are officially no dummy. So, if I claim: Test result 5F (limit of comfort)"according to the EN13537 norm" then nobody should take it for cash money.
But, I will admit, that the basic EN13537 norm idea, is a step in the right direction.
But this step is not finished yet, until the norm and the claims made in it's name, is under control. It's the wild west.
The UIAA control's hard wear climbing equipment claims, and go in and certify the gear. Makes sence: Your rope has to resist, as your helmet and harness and biners....Any body can understand, that this is vital and life saving.
To be hit by a falling rock, can have deadly a consequence, but where's the difference, if a non experienced outdoor/climber believes his gear can hold a negative 20, and discovers that once 3 days in, that at 0 it's on the limit? At times it's impossible to back out! (And I personally know from experience how this feels)
The UIAA, should take their responsibility, and propose a test in their own lab, specially once it comes to expedition and winter oriented sleeping bags.