Yes, I'm pretty familiar with metabolism. A biochemistry degree + seven years in a research lab gave me a reasonable grounding in the theory, and running (another) ultramarathon last weekend made me very aware of how it works in practice.

My comment about men and women was more one about how the brochure / web site (or wherever the quote came from) seemingly cherry picks the information that shows their product in its best light. I wouldn't be surprised if the next version shoves a pig inside the bag and uses whatever temperature it feels comfortable at in their advertising: "a great night's sleep at -40C say our test porkers; and it protects down to liquid nitrogen temperatures so it should easily be good enough for any nuclear winter our politicians generate while trying to fix global warming. Buy now - 20% off stock clearance offer."

Couldn`t know that you are professional but thought maybe someone didn`t know....
My RESPECT for ultramarathoning

As an online vendor you have to decide which kind of details you offer to convert interest into an easy sale.

Being in sales all my life means being in direct contact with critical thinking buyers and at once delivering satisfying answers to every kind of stupid and intelligent questions. By this I can tell you that intellignet questions got less and less over the years.

Meanwhile a lot of buyers are only interested in customer reviews and often these are the effective arguments to drive a sale. These type of buyers is steadly growing, they ask more on facebook or on amazon than in forum or to the manufacturer/distrbutor.

Sorry but as ignorant the buyer group grows as easy it is to sell bullshit with nice buzz words and funky graphics. Makes me earning money much easier...So with your words pigs could have a potential in future to be a real sales argument...

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The phrase 'pig in a poke' is what I had in mind.

I guess 'honest, decent and truthful' is laughably simplistic in todays sales environment. One step ahead of the police is probably closer to it.

I've been buying and using cold-weather sleeping bags since the seventies--before that, too, if you include those gigantic, kapok-filled monstrosities so common before the advent of modern synthetics. That being the case, I can report that you couldn't really trust temperature ratings back then, either. Many companies rated their bags for survival (i.e., you probably won't die during the night at this temperature) but described their ratings as if for comfort.

More reliable ratings could be guessed-at based on measurements of actual loft--same as today, although the manufacturers were apparently very good at fluffing and plumping to achieve maximum measurable loft without much bearing on what happened during actual usage. I note that the link given by the OP doesn't seem to offer loft measurements, and this alone would rule out a sight-unseen purchase in my book. 50 years ago, as today, the buyer had to draw their own conclusions based on whatever scanty data was provided--and tune out the sales staff unless by chance in the presence of one who was both experienced and honest.

I've always discounted temperature ratings by at least 20 degrees F, often more. I've discounted further to allow for damp insulation when appropriate, and further still if not planning to use a tent--a small tent is worth 10 or 15 degrees, a larger tent somewhat less. Then I try to allow for general states of exhaustion or inadequate blood sugar, either of which makes me sleep much colder. My resistance to cold (or ability to generate warmth) has deteriorated as I've gotten older, too. In all respects, YMMV.

Mark

Reminds me of an aircraft mechanic I once met, he was changing a bearing which had been dunked in liquid nitrogen to shrink it. The company provided heavily insulated gloves to handle it, but he evidently thought they would be OK to use to pick the bearing up out of the liquid. Of course the liquid soaked straight into the glove....

Thanks for the discussion, so it's exactly what I thought, just a number to rate one against another and doesn't actually tell me anything useful unless I have extensive experience of at least one sleeping bag already rated against that standard.

So for my first bag I need to just buy one and see how it goes, based on the advice of a shop assistant and some YouTube reviews

May as well ask "what's the best tent/oil/helmet/travel bike"

There are plenty of review sites around though - do a few searches for "best 3 seasons sleeping bag" or whatever. By the time you've read through a bunch of those you should have a fair idea of what brands and models fit your bill. In my case I was surprised to find fit came into it as well - the first one I got was way too tight round the shoulders, so being able to try them on in the shop is a plus.

This is an important point. A lot of manufactured stuff is designed to spec out well, without regard for real-world utility. The best temperature ratings in combination with total weight can be achieved in a very narrow bag with a short zipper. This *might* work well for a very narrow person who also happens to be perfectly content sleeping in one position all might, straight as an arrow with hood drawn and hands at sides. If this is not you (as it's definitely not me), you might need a much wider bag with a full zipper--it'll show up with a much higher temperature rating for the same weight, or a much heavier weight (and larger packed size) for the same temp rating.

Score this one in favor of brick and mortar shops, where you can measure your own loft and by all means try the bag out yourself before buying. If your first bag costs an extra ten or twenty dollars/pounds/Euros, consider it money well-spent.

Narrow bags are just awful to sleep in - in my experience anyway. There was a trend some years back to make bags that tapered from the hips downwards so that both legs were held tight together. The idea (presumably anyway) was to cut out 'dead space' and so keep everything warmer. It sounds great in theory and I even bought into it with my own money. That was the only bag I've ever gotten rid of; the psychological effect of feeling like your legs have been bandaged together made sleep impossible.

Experience has also taught me that sleeping bags don't just have minimum temperature specs; they have ranges. That is, a given bag is (more or less) usable between a temperature where it's too warm and and one where it doesn't keep you warm. If you buy a bag with better low temperature performance than you're likely to need 'just in case', it means you've bought one with a lower high temperature performance - and higher temperatures are where most bags are actually used. My worst experience has been using a bag rated to -25C when the night time temp didn't fall below +25C. It was absolutely unusable - and likely to become permanently so with the amount of sweat involved in try to use it.

Imho, if you save money in spending for your sleeping bag and mats you will never get an expression how it`s possible to get a comfortable, warm and relaxed sleep. If you want to find out if you are a camping person it maybe works. Better try this in an area not too cold.

If you go alone think about the security aspect a well relaxed body and mind will provide when you are in a remote area. Accidents or mishaps are often caused by exhaustion! Sleeping well and relaxed plus adequate food is a basic requirement to resist safe and powerful in extraordinary circumstances!

This should be enough value not to be to price focussed when buying gear you will use daily and which will last long times if it is the right quality. But ok, everybody has a different sight of this...



What about shapes and isolation?
I like the mummy shape with a built in neck warmer area in cold areas. If I am going to hoter areas or zones with high air humanity, I prefer egg shape with synthetic fibers because of fast drying and less needed isolation.


Mummy:
+ shape balances isolation ratio, space, comfort and weight.
+ follow body contours
+ Less pack size
- less space for moving sleepers

Egg:
+ more space for moving sleepers
- less isolation
- compromise of isolation/comfort

Comparision of down feathers or synthetic fibers:

Down feathers:
+ best isolation in volume/weight ration at duck/goose feathers mix 50/50
+ lighter in weight compared to synthetic at same isolation level
+ smaller to pack
+ absorb/give moisture -> better sleeping climate
+ long life span
- sensitive against moisture/wetness
- longer drytime
- higher price

Synthetic fibers:
+ will warm if wet
+ drys faster
+ better/easier to handle in climate zone with huge air moisture
+ more rugged than down feathers ones
+ simple to care/easy to wash
+ cheaper
- heavier
- less compressible/bigger pack size
- sythetic takes less moisture -> different sleeping climate
- less life span



My tips as general advice for those who don`t know:

- Take out your sleeping bag before you start to sleep and shake it up. This will give your sleeping bag time to puff up down feathers/synthetic fibers and isolation will work better.

- Add an illuminating (shoe) band or similar thing to the slider of the zipper. Provides a safe, easy and fast pull if circumstances needs this

- Always wear dry cloth, never wear sweaty ones.

- If it`s cold, do some warm up exercise before step in the bag. A "preheated" body warms the bag easier.

- If it`s cold use an inlet of silk or merino wool. Keeps you warmer and bag`s sleeping life time expands / dry time in the morning will be reduced because of less moistures given to downs/feathers

- Fill your water bottle with hot water when your cooking and place it it in feet end of bag before sleeping.

- Give your sleeping bag time to dry in the morning

- Don`t roll or folt the sleeping bag. If you do this everytime the same way, you will break and compress the compartments of filling/downs in same place. This ends in loosing isolation through less denseness.

- Start packing sleeping bag with the feet end first. Stuff it into compression bag than air inside the bag can easier pass off. Smaller packing!

- If your sleeping bag is equiped with a membran/covering impregnation, stuff it inside out to avoid compressing inside air.

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Hello

Yes, every bag has a range, like a jacket.
If you wear a jacket, that keeps you warm in a cold skandinavien winter at -25°C, on a nice summer day with +25°C you will sweat.
A bag rated for -25°C is big and expensive, buy and use equipment for what it's built.

sushi

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My RTW:
http://www.youtube.com/user/MrXt660ztenere

I think mine is rated to -10 or something like that. On a recent trip round Scotland I was sleeping half unzipped with my arms out to try and maintain a comfortable temperature. My wife, with a cheap "2 seasons" bag, reported she was cold. On balance I reckon it's better to have a bag that is "warm enough" on a cold night than to wear every scrap of clothing and still be cold. It's less weight and bulk to carry (as is a bag liner to protect it from sweat, pros and cons).

Ratings can give you an indication what the bag is for but its not only the bag that relevant.
What kind of sleeping mat you use, what kind of tent, do you use an inlay for your sleeping bag?
That are all things to consider before yoi choose the right bag for you.

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www.ibahabs.com

Honestly, for camping gear this is a reasonable approach. Combine "buy a cheap sleeping bag and see how it goes" with "take a short trip and see how it goes". A basic piece of camping gear from a discount sports store will either a) let you understand what you hate about it in detail, so that you can then decide for yourself how much money it's worth to you to not experience those downsides and shop accordingly, or b) actually work just fine for the limited purposes you have for it.

Hello

Yes, you have to buy your first bag and figure out what you need.
But, just don't buy anything, go to a store that is specialized on quality bags and has sales personal with knowlegde above reading what's on the price tag.

Youtube can be a good help if you find the right channels, stay away from influencers and "survival-guys".

sushi

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My RTW:
http://www.youtube.com/user/MrXt660ztenere