I would like to add to this discussion the two marketing methods used by sleeping bag manufacturers (sleeping bags are a bit of a fetish of mine).
You have on the one hand, the ultra-small, ultra-light idea. The most extreme example of this is the bags that Snugpak produce. The idea is that they quote the extreme temperature rating (or none at all - eg many are just called "2/3 season" or something), along with weight, so customers come along and say "Wow! What an incredibly small and light bag!" - and it's cheap too. The truth is that the rules are bent to breaking point when temperature ratings are quoted - obviously, a 1 season bag is easy to make smaller than a 4 season bag, but package it as a 4, then it will easily dominate the market on simple size and mass. This however can be a dangerous approach, as people buy bags rated at say -10, for use in conditions down to -8 or so - and end up so cold they can't sleep. Worse - the new EU standard that is coming in gives new definitions for "Comfort" and "Extreme" - Comfort appears to be sleeping through the night without being so cold you wake up, and Extreme is sleeping through the night without suffering permanent injury. I can't convey (even if I could, I think it would be moderated
) just how angry I am about this - and how incomprehensibly stupid anyone who thinks up such definitions is. The new regulation also hits bag makers of low temperature bags hard, as below -7 celsius the rating system overestimates the insulative power of the bag. This is of course even more dangerous.
The other approach is to make bags that appear large and heavy, but in fact are simply true to their rating. The best example of this is Nanok. The marketing works on trust - the customers will always have a toasty warm experience in their bag, and will never have problems in that department. This does have two drawbacks - the bags are heavier than other bags with the same label (
NOT those with the same insulation - this is
very different), and so perform more poorly at grabbing customers for the first time. It's a system that works better on recommendations to friends. Nanok bags in fact consistently outperform their stated temperature ratings - I have used my Endurance -25 in -30 in just underwear with no problem (see below). There is an article on the Nanok site about temperature ratings and includes information about the new EU standard.
http://www.nanok.no/temp.htm
Personally, I hate the first approach with a passion. I make no apology for quoting Stuart again: "There are lies, damn lies, and then there are Snugpak's impossibly optimistic temperature ratings". I have used a Snugpak "-50 Antarctica" bag in -30 and been forced to give up after half an hour. Ironically, I then climbed into my Nanok Endurance -25, and slept very soundly - and doubtless the temperature fell lower overnight, as that was in the evening.
This is why I very strongly recommend Nanok - well, that and the features on the bags themselves (no glue construction means you can machine wash at 60 degrees, and that there are no cold spots; there are armholes so you can eat your breakfast while still in your bag; there is a boot bucket so you can keep your boots on in the bag (the SF stands for Special Forces, as that's who use it) and also works as a water bag; and the bags can be zipped together for the extra warmth of another person). It is even possible to buy say the Nanok Endurance 0 bag, and use it to -5 or so, because of the honesty policy.
I am not affiliated or linked in any way with either of the above companies; I would just like to let you all know what I think is the truth
- hardly any space left for my other kit ... Since I've binned my stuff sack and use the method as above, I've got plenty of space for my kit and a fair amount of food / rations. The stuff sack has a new use: I keep my spare clothes, rations and / or other bits 'n bobs in it.
