sleeping liner, poly or silk?

I would go with the poly one because you are pushing your limits of your bag. It will be much warmer than the silk.

Waste of money.

For the weight, the warmth is negligible. I extensively tested even the best, $65 "25º" liners and found little difference in warmth, and if you check, reviews on liners are riddled with similar accounts from other users. Nearly every liner with a temperature rating has disputers in the reviews.

Think of a sleeping bag liner as a really, really loose fitting shirt. It's the thickness of a shirt, and that's how much warmth it's giving you. There's no "magic" to the sleeping bag shape.

For the weight, almost anything will do more! My suggestion is to wear all your clothes to bed. If you're looking for warmth, I suggest a warm baselayer. You'll use less material and it'll hug your body.

Silk is hydrophilic, unlike polyester or especially polyproplene.

As Max stated bag liners are a waste of money and weight. Bag liner makers lie, plain and simple.

You'll be much further ahead taking along the apropriate weight (thickness) of poly long johns. Which type of "poly" is up to you. The base layer is multi purpose item which is one of the keys in UL backpacking. You can wear it during the day if conditions require it. Nice for cold mornings.

It would be more work, but if you layered several thin, lightweight silk fabric together, it would be fairly warm for the weight. Thinking at least 3 layers of say 4.5 mm silk layers would actually be fairly warm for the weight and still fairly light weight.

Also, there is this unique and interesting fabric that is worth looking into, a bit pricey though.

http://www.dharmatrading.com/fabric/silk-wool-fabric-125mm.html?lnav=fabric_silk.html

It's a combo of 63% silk with 37% wool in a twill like pattern/weave (warmer and stronger than flatter weaves). It's about 12.5 mm weight, which is a little less than the 3 layers idea i suggested above, however i suspect the 3 layers idea will be warmer.

I think there is an easy math conversion to convert mommes weight to oz per sq/yd, but don't know it off hand. I also saw this from Denver fabrics, "we show weight per square yard for all our silks. With the exception of dupioni,
all weights are expressed in both ounces and mommes.
1 ounce (oz) equals 7.54 mommes (mm)." I'm assuming what they are saying is that a silk which is 7.54 mm will be equivalent to a 1oz per square yd.

Btw, i've tried the layering idea, so i'm not just speaking theoretically/logically but also from some experience. So if you layered say 3 layers of 4.5 mm silk together, you'll end up with about a 2 oz per square yd material if i'm reading the above correctly.

Another idea, to increase the warmth of such a system, though would really add to the pain in the arse quotient is this, get some light weight/thinnish dyneema/spectra or polypro cord and run some vertically spaced apart some, and some horizontally spaced apart some, secure it somehow. (fabric tape, then sewn threw also?)

This will create more air space between the layers, really increasing the warmth at not much weight. It's sort like the idea behind Fishnet baselayers.

If you did this, with 3 layers of silk (so two layers will have polypro cord separating the layers some), you will have QUITE a warm fabric at not much weight.

Also, betch ya, it's not been done before, so you will also have a very unique piece of gear. Now that i've thought of it, i think i'm going to do this myself! All in all, it would just be a lot more efficient/easier though to have more down. Or say an Apex over quilt with 2.5 Apex and lightweight silk liners.

I just bought some 200g merino icebreaker leggings (8oz). I also bought a neoair all season.

I have a syn tee shirt, a 8oz down anorak, and a squamish wind jacket. I would rather not bring my 14oz atom lt syn jacket due to weight.

Is this good? Thanks for all the constructive feedback thus far.

I have waterproof mt110 winter trail runners, and syn pants, or I may bring my running shorts and use the new leggings under them.

"As Max stated bag liners are a waste of money and weight. Bag liner makers lie, plain and simple."

+2 or 3.. not sure where I'm in line. Tried a synththetic bag liner and was very disappointed. Tried sleeping with and without two consecutive nights and felt no difference in comfort other than the bag liner was award to work with. YMMV.

Based on what you've listed, I'd personally be warm to 20* with my 30* MB bag. I'm a warm sleeper and I know other hikers who would be miserable. If you're bringing rain gear as well and can throw that into the mix, you'd probably sleep fine.

"other than the bag liner was award to work with."

What does that mean?

–B.G.–

I have some silk liners, cheapo-s from Academy, mummy shaped. Trimmied it down a bit. I don't use them to add warmth but for comfort and to extend the time between having to wash the bo/dirt/ect out of my bags. In the summer I use them as a light blanket when it is too hot at night to need to get inside your bag.

""other than the bag liner was award to work with."

What does that mean?"

The liner I used did not have a zipper. I don't like sleeping bags, bivys, or any sleep system that I have to struggle to crawl into. I'd rather have some sort of side entry and eat the weight penalty. I also felt like I was getting tangled in it all night. If I would have noticed any improvement in comfort, I probably would have given it the benefit of the doubt or modified it but based on my experience, it was meritless in any configuration.

Again, YMMV.

Edit Ahh….. award was supposed to be awkward.

I sewed my own silk liner out of material from Thai Silks, and I left one side of it open to match up with the zipper side of the sleeping bag. To avoid getting tangled in it, use about a half-dozen safety pins to bind it to the inside of the bag.

Most thin liners of this nature have almost zero affect on warmth. However, they do tend to keep your sleeping bag cleaner. The liner can be rinsed out and dried quickly.

At some European huts, they furnish the main bedding, but the traveler furnishes the silk "sleep sheet" which is about the same thing.

–B.G.–

Again, it would be more efficient to make an over bag with some apex if you want to to increase warmth, or even a "panel" to go over your core. But also like I said, it doesn't seem to make much sense, but I've found multiple layers of silk to add some noticeable warmth (nothing compared to down or even Apex though).

Here is one experience. I had sewn together two silk liners with a piece of 5.5 ft of Apex in between on the top and in mid March at an open hut at SNP with a low of around 36f, slept OK except for the somewhat strong wind that started ripping through later that night. Minus the wind, I was surprising warm with that tiny piece of apex and two layers of silk. I've also had a long run of silk fabric, folded it over a couple of times creating 3 layers and got nekked in my cool house in the winter (I try to keep the temp around 60) and again found it surprisingly warm.

Something to keep in mind about cold tolerance… even if you have decent cold tolerance on average, right now, chances are its going to suck. Mine does right now (and I have decent tolerance on average), because we've just got out of Summer! By spring time, my cold tolerance is way up, but not now… so I would err on the side of over doing insulation rather than under doing it.

I apologize to any Southern hemisphere based folks for the gross over generalization…

"Hi, my name is Justin and i'm a recovering Hemispherist"