Western Mountaineering Sl Bags

I find WM bags to be comfortable down to the rated temps, but I am a warm sleeper for a woman. This is with just a base layer on.

WM bags are rated to their "comfort" zone. Whatever the bag is rated for, you should be warm and comfortable at that temperature. I can sleep without layers in my MeagLite 30 degree bag at 30 degrees, and I do not get cold at all.

I don't know the answer to the female question specifically. I use the WM standard bags (6' length), but am relatively wider in the shoulders and not so much hip as many women (I fit the 62" shoulder girth bags best). I don't know if/how that would affect the warmth, but if a women gets the right size (use the supplied measurements to work it out), then she should be comfortably warm down to the rated temp of the bag rather than miserably cold.

Has it been established that women have universally lower tolerance for cold, or sleep colder based on some physiological difference from men?

That aside, it seems the most effective way to guage how well a bag will insulate across body types, manufacturers, etc. is to base it on quality and quantity of down.

Backward logic suggests that you are working to help a female select the right bag based on a previously established knowledge of european warmth ratings. Determining what the quality and quantity of the bag with the preferred rating contains should drop you right in the "fun" zone of another bag manufacturers offerings.

That aside, I would be confused why your selection set already includes such a wide range of bags? I have a hilite and an ultralite. In addition to some key design features, the ultralite has twice the down. That is a huge difference from an hilite, which is a bag only to be used in warmer weather or in conjunction with insulated clothing.

I think by selecting a manufacturer like WM, or Marmot, or Feathered Friends…you are probably doing yourself the biggest favor of having the best down to start with.

"Has it been established that women have universally lower tolerance for cold, or sleep colder based on some physiological difference from men?"

Most women have a lower BMR than most men. This difference comes mainly from a decrease in muscle mass and an increase fat mass. They also have reduced circulation to the estrogenic fat deposits on hips and thighs. These areas, anecdotally, may need more insulation in women. BMR can also vary a lot more in women depending on their estrogen status, i.e. when estrogen is high (becuse of phase in cycle or oral contaceptive use), their BMR is higher and they may feel the cold less, but still no where near the heat output of an average healthy male. This is a gross generalisation, for instance women going through menopause may have low estrogen levels yet suffer from hot flashes, but the general trend seems to be that women 'fell the cold' more than men.

Without the confounding factor of estrogens, women have a body composition adjusted BMR around 5-10% lower than men of the same age and activity level.

"Women really do feel the cold more than men, but this is because they are better at conserving heat than men. Mark Newton, a scientist at W.L. Gore, the company that makes Gore-Tex, and a researcher at the University of Portsmouth, explains: “Women have a more evenly distributed fat layer and can pull all their blood back to their core organs.”

However, this female heating system means that less blood flows to their hands and feet, and as a result they feel cold. So there is literal truth in the old saying cold hands, warm heart. One theory as to why women have evolved this system, says Newton, is to enable them to survive freezing temperatures. Women carry less fat and muscle mass than men, and so need a more efficient technique of protecting their core body temperature.

Research also indicates that women's perception of cold varies during their menstrual cycle, says Newton, with the core body temperature often changing by more than 1C. A study in 2001 found that women's core temperature rises in the luteal phase (the post-ovulation phase) of the cycle. The researchers also found that women on the Pill have a slightly elevated core body temperature."

Thanks for all the feedback. It might have been a sneaky way of asking the question, but I am actually buying the bag for myself. The real truth is that, while I used to T-shirt in the snow and use a summer bag all year, all that changed after serious illness & the consequential treatments, which combined with ongoing meds have left me rather wimpy when it comes to cold.

Through expensive experience have found that my comfort level now matches the euro standard for comfort (ok, so what if it's for a woman), which is sometimes very different to the ratings seen on US bags. The ratings on WM bags seem to translate to the comfort zone for healthy males without a baselayer, which is what is called the "limit of comfort" rating on the euro standard (i.e. women would wear a thermal layer also).

The reason for the range of WM bags mentioned in my post was just me trying to work out which one would suit me for which temps – i.e. do I get a highlite or summerlite for autumn, do I get a summerlite or ultralite for winter, etc.

I'd love to look at the marmot bags, but I can't get them in Oz or NZ. BTW, with the exchange rate, WM bags in Oz are more than a dollar per gram (more than $30 per ounce), hence my desire to get it right!

Based on the feedback I think I've now got a better idea.

If you feel the cold (and 59" shoulders is OK for you), then I think your best bet is to get just the Ultralite and use it all year round. Sure, there's a weight penalty for the warmer months when you may not need such a warm bag, but it would be the cheapest and most comprehensive option (you will never be cold). The other good option is to get a Summerlite, and add a good down insulation layer underneath it for colder trips. Keep in mind that with the second option, you may need extra width in the bag to accomodate the insulated layers.

Not sure what you mean by SI Bags? WM gives their ratings in degrees Fahrenheit and other American units, and they also have a metric specification chart which is the same information, but converted to SI. 0 degrees C = 32 degrees F and so forth. The numbers are different but the meaning is the same. Just go by what people on here say about the bags and use the temperature figure that you're comfortable with to derive meaning from that.

er, don't puzzle, "Sl" just shows that I'm too lazy to type more than the first two letters of "Sl-eeping".

Ok…I learned quite a bit by asking the question. Good to know.

Craig, you seem to approximate my size, and I have a regular size ultralite. That should fit you well, and offer you far more of a comfort range than the highlite. This assumes you are going to trek in the higher elevation zones during summer or use it in shoulder seasons. It offers a full zipper and baffling which makes it worth the extra $100 over the highlite. I guess I am not as keen on the Summerlite…given to your point, for strict "summer use" I would default to a highlite…but if you were going to buy one bag…the ultralite should give you the most versatility.