fluxlib wrote:If you look at Marmot's site, the pinnacle has a better EN rating than the helium even though they are both "15" bags. The pinnacle sneaks another 6 or so degrees in there. I stumbled upon this because I exhaustively research these pieces of gear, to the point of insanity really, maybe I have a problem? The pinnacle has the internal draft collar while the helium does not, it's more of a passive gasket around the face, but it works fine.
I do like that Marmot gives these results on their site and I am very impressed with my helium bag, it was a good value to me for 3 season backpacking, a very well thought out minimalist bag. They certainly aren't the only game in town though, and I was looking at a couple WM bags as well, would not hesitate on one of those either and by all reports, their temp ratings are accurate if not generous in a good way. I did score the Helium on sale, so no regrets!!
Since the ratings are pretty skewed across manufacturers, I would look at things like the fill weight, girth of the bag at various points, the shell material, features like draft collars, down loft, and overall weight. In most cases, equivalent bags (loft, temp, size) are within a few ounces of each other for the most part.
The info on the Marmot site is very interesting - I was just wondering whether there was a standard for sleeping bag temperature ratings and now I know that there is (EN13537)!
What's interesting is that different manufacturers appear to use the EN standard in different ways, and some manufacturers use it differently even within their lineup of bags.
Out of curiousity I decided to check what the EN rating for my 15F bag (MH Phantom) is - MH says that it's 15F for lower limit, which I gather is the lowest temp. an average man in a curled up position can find comfortable. The rating for "Comfort," which is what an average woman lying on her back would find comfortable, is 26F (the woman's version of the Phantom is rated slightly warmer). I.e., Mountain Hardware rates their bag based on lower limit, not comfort limit. I've tested my bag at 15F and found it quite comfortable.
The Marmot Helium, by contrast, which is also a "15F" bag, has a Comfort limit of 22F and a Lower limit of 10F. Looks like Marmot decided to peg the advertised rating of this bag based on the number halfway between the EN numbers.
On the other hand, if you look at the Marmot Plasma 15, also called a "15F," it has an EM comfort rating of 29F and Lower Limit of 18F (i.e., the advertised rating is below the EN limit of what even a curled up man would find comfortable). Likewise, the Marmot Lithium ("0F") has Comfort rating of 18F and Lower Limit of 6F, which is higher than the advertised rating. Wierd, and fascinating to gear geeks!