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Effectiveness of sleeping bag liners

Hi All

first and foremost, I wanted to thank the community for the help they've provided so far in their answers.

Anyway, One more question, this time about a liner. I have this Sea to Summit liner:

Though I am yet to try it in the field. The company claims that it increases sleeping bag performance by up to 20°F (11°C). Was curious about two issues:


1. How much really do liners of such sort increase the performance of sleeping bags? What exactly does it mean that the performance is increased by up to  20°F (11°C)? Even the conversion from Fahrenheit to Celsius doesn't add up.


2. Can I count on a liner to provide extra warmth when coming to choose a sleeping bag? That is, suppose I need a sleeping bag for a comfort zone of 0 degrees Celsius (about 30 degrees Fahrenheit) and I find a good sleeping bag with a comfort zone of 5 degrees Celsius (about 40 degrees Fahrenheit) - can I buy this sleeping bag and use with the thought of the liner providing extra warmth?


thank you for your help





Ah, the scam of sleeping bag liners.

They do work... but not nearly as well as they claim. I would say they add maybe and that's a big maybe half of the claimed benefit. I do not think they are anywhere near worth what they charge for these liners.

Their big benefit is keeping your sleeping bag much cleaner.

If your looking to ad warmth to your sleep system you usually get more bang for your buck from ground insulation.

+1.  the main benefit is that liners keep body oils out of your insulation, which will meaningfully protect the loft of the insulation.  Your bag will last longer and work better with a liner.

in my experience, no fabric bag liner will give you more than 5 degrees of temperature range, if that.  If you want the option of adding warmth to a sleeping bag, buy one that is roomy on the inside and wear additional clothes while you sleep.  wearing a down sweater would provide a much, much bigger boost in warmth than any bag liner.  

Liners aren't needed to keep your sleeping bag clean---just wear your baselayers and long johns when you sleep.

Plus, liners are claustrophobic as mummy bags tend to be confining when zipped and adding a liner will really keep you confined.  Have you ever woke up in the middle of the night overheated and gasping for air and your liner zipper is behind your neck and your bag zipper is bunched up around your shoulder?  Good luck and don't panic.

Plus, if you buy a bag that says it's rated at 30F, count on it to work 15 degrees higher, at 45F.  Real world conditions always lower a bag's efficiency because your nice bone-dry lofted bag at home will never be as dry and as lofted as out in the field on a long trip.

SO---go overkill so you can sleep comfortably at night and plan for the 15 degree offset and if you're hitting 20F, get a 5F bag.  This will save you money in the long run.  One purchase---and no more---and no liner.

Overkill will save you from the hated liner route.

I've had good experiences with sleeping bag liners, but agree with the sense of the group that they tend to exaggerate the benefit.

I'll bring a liner in the fall, when I have my 45 degree bag, and am suspicious that it might hit freezing.

I am leaning the same way as tipi. Save weight on sleeping bag and wear your extra clothes to bed. You brought them why not wear them? Im using a lightweight bag and doing this very thing.

have to agree with Tipi and Sage. Wear your extra clothing. The liner just keeps your bag cleaner..

+1 on what the group says. liners are really just good for keeping your bag clean, nothing much else.

your nice bone-dry lofted bag at home will never be as dry and as lofted as out in the field on a long trip.

I meant to say---"Your nice bone dry lofted bag at home will never be as dry and as lofted when out in the field on a long trip."  Minor point.

Adding to the avice on keeping the inside of your bag clean: I use skin layers that are solely used as bed clothing - no dirt comes in the bag with me.  I also wash up daily at the end of the day after completing all the physical, dirty, and sweaty camp chores.  Thus my bags need a washing only about every 10 or fifteen years.

As for additional warmth; I am with Tipi, and don't like the confining feeling of liners and being bundled up in layers while trying to sleep.  I prefer to use a bag that I know will handle the anticipated temps.  Hence I have several bags to cover the spectrum of conditions I experience.  Many spend big buck on SUVs, bass boats, motorcycles and other toys.  The cost of additional sleeping bags is minor in comparison, especially considering the typical hiker will get decades of use from them.


Over the years, I have occasionally used sleeping bag liners that purported greater warmth. I never found any significant improvement, with one exception (which I will discuss below).

Yes, they keep the bag cleaner. but, as pointed out above, you can do the same by changing to clean sleeping clothes (full body, not just a pair of shorts), and changing to clean, dry long johns will improve the warmth of the bag significantly.

But, the important note here is "clean sleeping clothes", not your dirty, muddy, wet, sweaty clothes. I have found the few times I slept in my clothes off the trail, I was very uncomfortable and the clothes tended to get twisted all around. I have used everything from silk-weight to expedition-weight long johns to sleep in - as long as they were dry, they helped a lot with warmth. But damp, sweaty, or damp with rain that got inside my outer layers is distinctly uncomfortable (plus just gets the bag's insulation wet - really bad if it is a down bag).

The one exception to noticeable benefit to a liner that I have found is using a vapor barrier liner. This is not for everyone, nor is it for every season and situation. I find it works very well in Arctic and mid-winter conditions. For one thing, it keeps your body sweat from getting into the insulation and freezing there. It is supposed to work by the body sensing when the humidity inside builds up to a certain level, and the body slows down the perspiration function. I do find that I have less need to drink water during the night with a VBL in the sleeping bag. BUT... VBLs are not for everyone. Some people find them like sitting in a sauna, while others find they work really well.

Bill I couldn't agree more. I too have tried various liners with very little increase in insulation. The exception is with a VBL. Anything longer than a single overnight trip and a VBL is essential, even with the newer synthetic bags. It can increase the temperature range by 10C or so while preventing your sleeping bag from frosting up in cold weather. A vapour barrier liner is a real life saver for anyone camping out in the winter months. Anything else is not worth the weight.

I'll go against the main opinion here.   I've used a silk liner for years now, although the most recent purchase was from Vietnam, I don't like its fit. The brand you mention does not carry light liners from what I have always seen.  I use the lightest weight silk liner I can find.  My feeling is, you save your clothes to wear to bed when it gets way colder than you are prepared for.  You are sol if you count on your clothes for expected temps and it turns 10-20 degrees colder.  The main reason I use a silk liner is the rest of folks opinion, to keep the bag cleaner, although I wish I could find some lightweight bottoms to wear, I could get by with a clean shirt, but then what to do with your greasy head? If this could all save weight over a liner, I'd love it.  Make a silk hood of some sort?  I do find liners add some warmth, it is hard to measure unless on a warm night, you have to hang out of your bag for a bit until it cools off in an hour or so, then you can feel the difference.  I'm used to falling temps out west here. 

I have been thinking this spring that if I get another bag or quilt, with me getting older too, I maybe should get a lower temp bag to use and do away with the liner and just wash the bag/quilt more often.  I don't think I'll make SUL status (under 5 lbs.), but it would help a little bit more as I am under 8 lbs. now for my base weight.


My experience with a VBL is about that same as with a liner but worse---as Bill S says it can be a sticky sauna.  And confining.  And let's face it, my Puma down bag can easily take me down to -15F w/o the need for a VBL.  So . . . . . .

If I was doing -30F all the time I'd consider it.

Otherwise I do not consider a VBL essential on winter trips in the cold and humid and wet and frozen and snowy Southeast US.  Even on long uninterrupted trips.  The fact is, if I wake up in the morning with a slightly moist bag I just hang it out for an hour before shoving off---just enough time to dry the shell and bring back the loft.

Hikerduane--a silk liner is sweet but then again I wear a long sleeve silk turtleneck top baselayer and merino leggings so in a way I'm already in a moveable liner.

Tipi, I toss and turn a LOT and am awake when doing so, not having to roll inside the liner would be pretty nice.  Getting old, hard to change my ways, I need to check out silk clothes, but then, there goes my base weight back up.  I'll have to mull things over more.


I toss and turn constantly and so my dislike of liners.  In fact, I much prefer an open down bag in the winter vs the same bag zipped up into a mummy.  SO . . . . I go overkill with a down bag so it will work as a quilt longer in lower temps.  My WM Puma is rarely zipped completely in the winter unless the temps dip to 10F or below.  This way I can toss and turn w/o the confinement of a zipped up mummy bag.

Why not just use a quilt then... save some weight too.

Because a quilt doesn't have the overkill mummy option (zipped) when temps hit 0F or below.  My Puma works from 50F to -15F.

I have used both a fleece liner & a silk liner, I found the fleece added some warmth to the bag (not a lot), the silk was not noticeable in that regard.

A few years ago I switched to wearing a clean base layer in my bag, for me this works better. When I get up in the middle of the night to answer the call of nature I am already dressed for chilly / cold weather, all I have to do is slip on my boots, grab my flashlight & and I'm off. 

To answer your question, I think it is best to pick a bag that will get the job done and figure on about 10 degrees colder than you expect to encounter.

There are a lot of little tricks you will hear of like using a liner, or sleeping with a bottle full of hot water, or hot rocks, sleeping next to a fire, etc. I have tried all that stuff and I think you are better off with bringing an adequate amount of insulation with you from the get-go. This can be a combination of sleeping bag, quilt, insulated sleeping pad, the right design of tent, etc. Then, a bag liner, base layer for sleeping in, or bottle full of hot water, is just an added bonus for extra comfort.  

I want to get a summer temp quilt next year, that will save me maybe 6 oz. over what my WM Caribou (35F) weighs.  I've already had to endure one cold morning this season in it, as the forecast called for 36F and it got to 26F.  I had to pull my Golite Coal jacket over my chest and I was fine.  Except for my wool sock encased feet.

I may be focusing on one narrow, season, specific bit of gear to save as much weight as possible, financially, a piece of gear with a broader range would be best.  I'm mainly focusing on summer weight, for snow camping, since I bring so many stoves to use, weight is not a primary factor, although I have a much lighter pad combo now to maybe offset what stoves I bring. :)  The pad combo is also less bulky than using a Exped DAM9 with a ccf pad as insurance.


Quilts work fine for any temp if you have the correctly rated one for the conditions. I have used my winter quilt down to as low as -23. It's a -15f rated quilt. Snap the footbox closed and cinch it up around your shoulders and its just as effective as a mummy bag at keeping the cold out.

Problem with cinching around the shoulders is that a night of tossing and turning at 0F quickly removes the "sealed quilt" from around parts of your body and you end up with cold spots.  The beauty of a good mummy bag is that you can twist and toss and turn and spin all night long and get no cold spots and make no efforts to seal up those cold spots like with a quilt.

You're in a cocoon of warmth needing no more conscious thought than to zip up before nodding out.  In fact, an overkill down mummy bag could be a little too warmth fully zipped at 0F---which is a good thing if I'm certain to get -10F the next night.

Plus, a good down mummy bag has an insulated bottom which during a night of movement becomes your side insulation or even your top insulation if you shift around a lot.

This has been discussed in the link below---

I'd worry about getting cold using a quilt as some comments have been made elsewhere, so with limited funds, a summer quilt would be fine as I'm only concerned about reaching a record low weight for my summer bp trips.


I guess if you toss and turn a lot then a quilt would not be the best choice for you. For me, once i lay down in my hammock I am so comfortable that i barely move until sun rise. And quilts work great for me, I have never once woken up cold because of a quilt issue/draft etc.

I'm not aginst liners, but I like duel purpose gear and already carry a base layer in all but the hottest weather.  So I just put that on before I jump in the bag; treating my bag as just another component of a good layering system.


It seems that a baselayer is far more versitile than a liner. You can tailor the baselayer to your trip: you can wear the baselayer when you're cold outside of your bag or quilt, a baselayer is more easily washable, you can wear one part and not the other, and they hang nicely off the back of our packs.

Which is better for the weight, baselayers or liners? Nobody really knows right now. But, my little gear company is working on a new way of testing sleeping systems, using tiny sensors. I hope in a year or so, we'll be able to actually test these sorts of questions too.


I agree, the base layer is more versatile. I have noticed several advantages for me since I switched from a bag liner. Others may have different needs, but I really like wearing the base layer as opposed to a liner.

the Fahrenheit Celsius conversion isn't working beacause its not absolute temp.,its difference temp.the conversion formula you are using is based on 32f/0c reference.i bought 4 sleeping bag liners on clearance for 10 bucks ea. with poly shell and fleece liner(approximately 1.5lbs.)they add comfort and insulation commensurate with their cost/weight,but the real advantage is versatility.the claimed 15f benefit ive found to be relatively accurate.for shorter trips with accurate weather predictions you can tailor to need.less sleeping bags=less money.

September 23, 2021
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