Sleeping Bags

Completely UN-scientific but was out last night and the temperature dropped to about -12 Used the Banshee and slept the whole night (10:15 to 07:05) waking up feeling comfortably warm. I know that in TNF Superlight that anything below about -4 and I'm in danger of being cold -8 or so and I WILL be cold.

Thing is the Superlight is rated to -12 comfort with the Banshee being -11 i.e. very similar. In fairness to the Superlight if it had been any colder then I probably would have needed to wear extra clothes. I was wearing a merino wool long sleeve vest with cotton boxer shorts and thickish socks.

SO in this real world test what makes the Banshee feel warmer? is it just a margin of error or something else my climbing partner pointed out the price difference but that shouldn't affect the rating as its a function of the bags manufacture i.e. welded seams rather than sewn etc.

Unless they have identical specifications, particularly in terms of the type and quantity of filling, I would have to think the obvious answer is going to come down to those differences. Along the same lines, how the filling is distributed in each would have some effect.

When you say "rated", do either of them specify EN13537 as the testing standard they have complied with?

Lies, damn lies, and sleeping bag ratings

Even EN13537only really gives a basis for comparison.

US and EU ratings vary, different test methods I suppose.
 
I find my roomier down bag cooler than expected compared to a snugger synthetic one, the fit is probably important.

The guys above are right: are you comparing EN13537 with EN13537?

TNF were the first manufacturer to test commercial sleeping bags using manikins, and that sort of testing has developed into EN13537, which is a manikin test conducted under specific conditions. As a result, it takes into account the bag design (including seams), and all sorts of other things, not just the bag's fill weight and power (as tog testing would do). For what it's worth I think EN13537 is a flawed test, but two bags tested side-by-side, by this method, should give results that qualitiatively agree with real-life testing. Of course, sleeping bag fit is diferent yet again: the manikin test won't work for you unless you're the same size as Hohenstein's Charlie.

The fit is a good point. Plus as people have said time and time again, some people sleep hotter or colder than others. Back in october I was out and about in derbyshire when the temperature dropped to -7 overnight - cold enough for rain to have frozen into the tent zip overnight which made getting out a bit fun - and was using an Alpkit PD400, which Alpkit rate to -3 for comfort. I was using it with a silk liner but wasn't wearing thermals (or anything other than shorts in fact!) and was toasty warm all night.

The best you can ever really hope for is a test which will provide a near-equivalent rating for any sleeping bag and then use your past experience to adjust the rating to yourself.