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How do the Sea to Summit sleeping bag liners increase warmth?
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mister jarvey
How do the Sea to Summit sleeping bag liners increase warmth? on 12/03/2012 19:39:41 MST Print View

Can someone explain how the Sea to Summit sleeping bag liners are able to increase the warmth of a sleeping bag? Based on specs, it looks like the different versions are just polyester. Can someone provide more info?

Seth Brewer
(Whistler) - MLife

Opinion on 12/03/2012 19:41:29 MST Print View

My personal opinion from using them is that they keep your sleeping bag clean....that is about for the added weight - you'd be better off getting a base layer and actually staying warmer and keeping the bag clean.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: How do the Sea to Summit sleeping bag liners increase warmth? on 12/03/2012 20:05:23 MST Print View

Well, I don't think they do very much actually, as far as increasing the R-value of the quilt goes.
But, they do keep the quilt clean, which in the long run is quite important, AND they do block drafts when they are wrapped around you. On the warmth side of things, blocking drafts can be quite important.


Dale Wambaugh
(dwambaugh) - MLife

Locale: Pacific Northwest
Re: How do the Sea to Summit sleeping bag liners increase warmth? on 12/03/2012 20:17:21 MST Print View

Just like another base layer really. As Roger said, they keep things clean, but I've always looked askance at the warmth claims on such things. Add that same weight to real fill and you would have a much warmer quilt/bag. They aren't cheap either.

Edited by dwambaugh on 12/03/2012 20:32:18 MST.

mister jarvey
reviews on 12/03/2012 20:17:58 MST Print View

Reviews on REI are quite glowing. Reviewers have stated that the liners actually do increase the temperature range of the sleeping bag by the advertised rate. The link I provided was for a 20 degree liner.

Dale Wambaugh
(dwambaugh) - MLife

Locale: Pacific Northwest
Re: reviews on 12/03/2012 20:42:01 MST Print View

Do the physics. A 20F increase under what conditions? It's all too subjective. I want to see the test results. The thing weighs 14oz, but all you are getting is a thin fleecy layer, about like wearing a Cap3 base layer. 14oz overfill would make a FAT bag or quilt. There are summer down bags that weight an ounce or two more than that. I don't buy it. Spending $65 could be a convincing placebo :)

Harris Goldstein
(hmgolds) - F

Locale: Minnesota
What I've been told on 12/03/2012 20:47:52 MST Print View

As it happens, I was looking at these last weekend at a local outdoor store that is very focused on backpacking. What I was told is that you can expect the liners to deliver about 5 deg less than advertised. So if it says adds 15 deg, you can expect 10.

I should have asked, but did not, whether this was based on personal experience or feedback. I assume not from any objective testing. If based on feedback, you always have the effect of people rationalizing their purchase.

I can see it having some effect in that it is another layer and it might be a bit tighter around the body than the sleeping bag. After all, even a t-shirt provides some warmth.

But I decided that lightweight polypropylene long underwear should work just as well, be cheaper, and be more versatile.

Max Dilthey
(mdilthey) - M

Personal experience on 12/03/2012 21:01:39 MST Print View

I'm not afraid to say it. I got suckered.

I bought the $65 Thermolite Reactor Extreme from Sea to Summit. Through extensive testing, I found that the material did little to nothing to increase warmth, a far cry from the advertised 25º.

First off I read "Can be used as a summer sleeping bag!" as fact, and brought it with me on a 30-day, 1500-mile bike tour across the northeast that included summits of Mt. Caddillac, Mt. Greylock, and Mt. Hurricane. We slept on Hurricane and it got to 40º; luckily, after 3 days of touring I established that the thermolite liner did next to nothing on it's own, and I grabbed a $30 fleece bag (Alps Mountaineering RAZOR). Had i just had the liner on it's own, I may still be shivering to this day.

I can detect no difference sleeping with and without the liner using the fleece bag.

I can detect no difference sleeping with and without the liner using a 20º synthetic baffled bag.

I can also attest that it blocks no wind whatsoever- the nature of the hollow-core fibers don't block a damn thing. With a 20º bag, this product is advertised to make my sleeping bag into a -5º system, and I'm still a bit chilly at 30º. I would argue that at -5º with no clothing, a 20º bag, and the liner, I would probably die.

If it is providing warmth, it's less than 10º as far as I can tell. I am disappointed, but hey- live and learn. It doesn't end up in my pack anymore- my Merino Wool baselayer does much more.

Edited by mdilthey on 12/03/2012 21:05:26 MST.

Travis Leanna
(T.L.) - MLife

Locale: Wisconsin
Re: Personal experience on 12/03/2012 21:05:56 MST Print View

Yep, I had purchased one a few years back expecting miracles. I promptly returned it since it did practically nothing in terms of increasing warmth.

You'd be better off gettign a light silk liner if you want to keep your bag clean.

jason quick

Locale: A tent in my backyard - Melbourne
bummed about liners on 12/03/2012 21:46:18 MST Print View

I've tried every type of StS liner, in the hope of capturing that magical 'warmth' they speak of.

Bummed every time. I just wear more of my existing layering system - problem solved.

eric chan
(bearbreeder) - F
spend on 12/03/2012 23:52:46 MST Print View

yr better off spending the money on a better bag ... or getting a synth overquilt/bag that will at least help with condensation ;)

michael levi
(M.L) - F

Locale: W-Never Eat Soggy (W)affles
marketing on 12/04/2012 00:42:34 MST Print View

I'm envious of this for sure, im certain they have made A LOT of money.

x2 on baselayers, either get lightweight or a midweight baselayer. They are multiuse because you can wear them in camp to keep warm.

Anthony Weston
(anthonyweston) - MLife

Locale: Southern CA
x on 12/04/2012 05:50:47 MST Print View

It's been my experience that a very thin foam 5 oz shoulder to hip pad on the inside of the bag or quilt in addition to a neoair or some pad, greatly increases the warmth; I'm a cold sleeper and this works for me. Also fleece socks.

Ben 2 World
(ben2world) - MLife

Locale: So Cal
DO NOT Believe the Hype on 12/04/2012 11:37:02 MST Print View

Do they still say 15F temp boost? My own experience:

o silk liner - temp boost of 2-3F
o Sea to Summit poly liner - temp boost of 3-5F

Phillip Asby
(PGAsby) - M

Locale: North Carolina
Interesting on 12/04/2012 12:01:19 MST Print View

One of our assistant scoutmasters is a pretty experienced backpacker, and works at REI part time for fun (he's retired) and he told us new dads not to bother with them - either wear more clothing or if you really want a liner (particularly for car camping) he advocated going to wal mart, buying a fleece blanket and sewing together your own liner (how is that for some MYOG promotion?). The only issue being weight somewhat and bulk in particular... Not that his word is gospel or anything but he could have told us to buy them and most would not have balked...

My son said he got chilled on our campout this past weekend. He was in a 20 degree synthetic bag - wearing long underwear, socks and a fleece hat, and temps were in the low 40s... I was comfortable to a little warm in long underwear, no socks and a 25 degree bag... so I admit I was considering one for the upcoming backpacking trip in February (our next campout). I think two things will happen - I'll review again how to use a mummy bag (you have to get all the way inside it and zip it up! not treat it like a blanket on your bed and have half your torso sticking out like he did a trip ago - when I told him to get down in it he was like wow this is a lot warmer! ahh to be 10...) and we'll up the clothes - probably fleece socks and a better set of base layers, maybe a fleece vest. All dependent on the weather of course.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Interesting on 12/04/2012 13:00:09 MST Print View

wear a synthetic or down vest instead of fleece

Travis Leanna
(T.L.) - MLife

Locale: Wisconsin
Re: Interesting on 12/04/2012 13:08:53 MST Print View


Many sleeping bags are very liberal with their ratings. What bag was he using? Look for bags with an EN rating; its one of the few "standards" out there.

Also, what sleeping pad was he using? Do NOT underestimate the power of an appropriately insulating sleeping pad!

As far as using a mummy can use it unzipped as a quilt with success. Just make sure you have an appropriate pad, bag, and clothing. Drafts can rob you of warmth as well, like if you're under a tarp.

If its cold, don't forget to insulate your head!

Hiking Malto
(gg-man) - F
A counterpoint on 12/04/2012 13:13:39 MST Print View

I have and will continue to use a S2S Liner along with my Golite UL20 quilt and bivy in the winter. I have had this combination down below zero at 12k in the Sierra winter so while I may not know the exact contribution of the liner I do know that the system does the job. Many have stated that there is a better bang for the weight. That is true if you are willing to have specialized gear for summer, fall and winter. But I believe this is one tool, of many that can be used to extend my normal three season kit into the lower temperature ranges.

Jeff J
(j.j.81) - F

Locale: Oregon
adds 25F? Nope. on 12/04/2012 13:23:33 MST Print View

I picked up the 25F liner a couple years ago in an effort to stretch the life of an old bag. It did NOT at 25F; it did add warmth, which any extra layer will do. If I'm generous, it added 10F.

It's one of the few items I've returned to REI. It just didn't come close to it's claims. If you want to keep a bag clean, get a silk liner for the lighter weight. If you want to be warmer, pick up a cheap puffy. That's what I decided.


Phillip Asby
(PGAsby) - M

Locale: North Carolina
Re: Re: Interesting on 12/04/2012 13:58:14 MST Print View

Travis - he was in an Alps Mountaineering Clearwater 20 (he is a scout and this was a scout direct purchase). Not the lightest but it compresses pretty well and I admit to not wanting to spend too much early in his scouting career in case he didn't take to it, not to mention withstanding a certain amount of scout abuse (I do talk to him about proper gear maintenance)... I don't think it will work to 20 degrees but figured we would be good to 42. He was on a Thermarest ZLite regular - so I think the pad was doing it's work.

Part of it I believe is technique, part of it is making sure he had the right clothes on, and part of it is him getting used to the idea that cold air around him doesn't mean he is necessarily cold. That last bit doesn't make sense perhaps but you feel the cold air on your face, but your body is warm - I know early on I could still think I was chillier than I am. A hoody might also work as he is a restless sleeper and drafts can be an issue.