how much does a liner or bivy improve a sleeping bag rating?

9:16 p.m. on April 1, 2009 (EDT)
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Fun gear-head question...

I want to improve my bag's temperature rating a little for the one cold night I'll face on a trip this year. (last night before summiting Kili) How would you rate a) a breathable bivi, B) a silk liner, and C) a fleece liner D) some other liner for improving the temperature rating of a down bag?

I know it wasn't designed for this, but I have found the mont-bell superlight bivi to add a bit - I'd guess about 5 degrees but I wonder what other people have found.

By the way - I don't want to go with a heavier bag as I'll roast the other nights on Kili, and probably never use it again when I get back


9:40 p.m. on April 1, 2009 (EDT)
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Well, Tim, I think you're gonna find that, just like with bag ratings themselves, there's no universally accepted and agreed-upon answer for any of the items you mention. That said, here's my quota of electrons for this:

I have a silk liner I frequently use, if nothing more than to keep myself away from the nylon. The maker reports that it adds about 10 deg (F) to the bag's rating--a frequent claim for these, from what I've seen--but while I'd give it credit for some increase, I think 10 deg is being overly generous. Maybe 5?

I've also used as a liner a light fleece blanket, and found that it adds quite a bit more than the silk does; I'd be happy agreeing that it probably does give me another 10 deg of comfort--maybe even a titch more.

I've not used a bivy sack, but from what I've heard/read, most are decorated with claims of adding 10-15 deg to the bag's rating. My guess is that's probably true, but I'm kinda stabbing in the dark when I say that. One other thing to note is that many folks report that bivy sacks cause unwelcome condensation inside, largely negating their advantage. Again, I can't address it from experience, and I'm sure it has a lot to do with what bivy is used, how it's used, etc. I'm guessing you've not had that experience, or you've figured out how to counter it effectively.

One thing I sometimes do on the bookend seasons is take my 20-deg TNF Cat's Meow bag, the silk liner, and a rolled-up light fleece blanket. The blanket, rolled up, serves as a pillow, and the silk liner is my contact layer, around which I adjust the amount of opening of the bag, draping thereof, etc. If I find I'm getting cold, I drape the fleece over me and use something else as a pillow. Seems to have worked reasonably well. It also allows me to have a blanket to cuddle up in around the fire should I so desire. Almost as useful as a towel. (You need to be a HHGTTG fan to get that last.)

Good luck. Enjoy your trip1

11:17 p.m. on April 1, 2009 (EDT)
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Wow - great answer. Worthy of the great publishing houses of ursa minor. Funny - I'm a Brit and I met Douglas Adams a couple of times before his sad passing.

You confirmed where I was leaning with a combo approach as it also gives me some options at the warmer lower levels. I also have 2 down jackets I can layer over the bag.

FYI - I have the montbell bivvy sack. Crazy light and Ive not had any condensation issues.It's not their gore-tex one, but lighter, (something like 5oz) and their customer service guys said it breathes better...

11:27 p.m. on April 1, 2009 (EDT)
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Hey Tim Pollard,


Nice fish, first of all.

Most of my camping is done above 10 deg F. Although I love winter time and what little snow we get in the Southeast.

I agree with Perry, I too have a silk liner, I think it adds about 5 deg. I prefer the silk over fleece but that is just because I prefer the feel of silk, I don't know which one is actually warmer.

I also have a bivy and think for me it helps mostly with adverting wind chill, depending on conditions it adds maybe 10 deg.

I also sleep in a base layer with heavy wool socks and a medium weight wool cap. To me this helps the most.

Also you may want to increase the insulating layer between your bag and the ground, many people here on trailspace use both a closed cell pad and a inflatable matress for colder conditions.

I'm sure some of the people here with more cold weather experience than me will offer advice.

12:23 a.m. on April 2, 2009 (EDT)
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I think most of your heat loss will come from the ground. I'd make sure whatever you're sleeping on will keep you warm at night. I use a Prolite 4 by thermarest, which I want to say is rated to ~15*. I like trouthunter's idea of using both a closed cell pad and a mattress. Remember that your sleeping bag has NO insulation on the bottom since you end up compressing it. Some companies (i.e. Big Agnes) even make sleeping bags with no bottoms to save weight. Your liners will not only add a little warmth, but also increase the longevity of your bag. You end up washing the bag a lot less since the liner is the one taking all your skin's oils and grime.


As far as the added warmth from a liner though, I'd guestimate that you MIGHT gain 5-7*. Maybe more if its fleece, and if its thicker.

12:39 a.m. on April 2, 2009 (EDT)
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I met Douglas Adams a couple of times before his sad passing.

Well I certainly envy you that. I enjoy his works tremendously. My favorite, actually, is Last Chance to See, a cooperative effort he did with some naturalist sort of bloke, describing their trotting 'round the globe to see living examples of species that might not be around much longer. My favorite was the New Zealand bird--can't recall the name--that tried to eat the windshield wipers of their vehicle. Easy to see why that bird's endangered, I suppose.

Well, gotta run. There's a party somewhere, and I've gotta get there before Arthur or Ford does something we'll all regret. ;-)

12:53 a.m. on April 2, 2009 (EDT)
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Tim -

From your earlier post on Kili gear, I would say forget the bivy and liner, and just wear your down or Primaloft jacket in the sleeping bag on the half-night you sleep at Barafu. You will hit the sack about 6 or 7 (should, anyway), then get up at 11 to midnight to start for the summit to arrive by dawn or shortly after (remember Kili is at 3 degrees south latitude, almost on the equator, so days and nights are almost exactly 12 hours each year around, unlike in Blighty). You really only need the jacket for the climb in the early dark hours and maybe only on the summit (I only used my Dolomiti on the summit just to stick around for 15-20 minutes to shoot lots of photos - most of the guides push people to start down within 3-5 minutes, "just take one photo, we go now!").

I would strongly suggest you take a good synthetic jacket, like a Primaloft. Remember you are going through a rainforest on the way up and are likely to encounter rain, sleet , and/or snow on the way up and/or down. Down can easily get wet, which causes it to lose its loft, hence lose all insulating value, where a good synthetic like Primaloft retains some insulating capability even when damp. And the jacket with your thermal underwear in the sleeping bag should provide plenty of warmth.

12:55 p.m. on April 2, 2009 (EDT)
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Thanks Bill - It's really helpful to talk to someone with real experience. By the way- 2 earlier questions:- The sleeping bag you thought "about right" (see our earlier exchange) - was that the 15F bag or the -15F bag? and is a cheap wal-mart poncho OK or is there something better?


1:35 p.m. on April 2, 2009 (EDT)
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I just posted over in the Climbing Forum my reply about the rating of the sleeping bag. With the jacket and your thermals, and sleeping only the first half of the night, a +10 to 15F bag should be warm enough. Kili is a pretty warm mountain for one so tall. And you will be sleeping at about 15kft, not on the top of the mountain.

I haven't looked at WalMart ponchos, but I would suggest a flash-coated ripstop nylon, which is what I saw the guides and porters using. If the WalMart one you are talking about is one of the plastic ones, it may not last the trip. OTOH, this might be the only trip you use the poncho, and the trails are reasonable, so you won't be getting it caught on brush or tree limbs.

Oh, yeah, one of the strong recommendations that the Porters Union and local guide services make (maybe "request" is a better term) is that you take any old warm jackets and boots you have to donate to the porters. So if you got a good quality poncho, you could donate that. Some people make Kili their once in a lifetime "high point", since it can be done by any reasonably fit backpacker who doesn't suffer from AMS. Since they will never use the gear again, they often give all their gear to the porters - jackets, wp/b parkas, boots, packs, etc.

Which brings up tips for the guide, cook, and porters. Look on the Adventures Within Reach website for a guide to appropriate tip amounts. Basically about $10/day for your guide, $8/day for your cook (and give the cook a bottle of Purell at the start and request he use it before preparing every meal for you), and $5/day for your porters. Get to know your assigned guide, cook, and porters, and if any of them provide special service, add a few dollars. But do not give US or European sized tips - the cost of living is much lower in Tanzania and a number of the porters will gamble it away within a few days (I got this from my guide Patrick and from a couple of my guides). Another reason for getting acquainted with your support group is to make sure that "John" (who isn't here right now, and you never saw) really was one of your crew (some of the porters will promise to give "John's" tip to him as a scam). And try to give the tips in individual envelopes with their names on them at the exit gate - not to the guide when you get back to the hotel who promises to distribute the tips. Most of the guides and porters are honest (I will vouch for EcoTours of Moshi in that), but I have been told that some are not. It is common for medium to large groups to pool the tips and split evenly among the porters and among the guides (larger groups have multiple guides who will hike alongside the clients) and among the cooks (you often don't see the cooks if you are in a large group).

6:54 p.m. on April 2, 2009 (EDT)
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I agree with Bill on sleeping with a jacket. When it gets real cold (-10F and below) i always sleep with everything on, gore-tex and all, and end up much warmer and ready to go in the morning. What's the point of carying all that warm gear if you're not going to use it at night?

Again, you can't go wrong with primaloft. When the weather turns real nasty around freezing, it could be the only thing that keeps you warm. It seems to stop rain as good as a rain jacket but breathes better.

Have a fun trip!!!

5:24 p.m. on April 8, 2009 (EDT)
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Hello Tim,

I am also climbing Kilimanjaro in September & was concerned, like you, if my +15 sleeping bag would be warm enough. I ended up ordering the Sea to Summit Reactor Thermolite Liner. Liked what others said about it, including how it breathes & how compact it is compared to the fleece liners. Best of luck on your trip. Paul

11:59 p.m. on April 12, 2009 (EDT)
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thanks paul. I think i'll go exactly the same way, although I like Bill's severalpieces of advice- in particular to wear a primaloft on that last night. After Bill's comments I bought a mont bell primaloft jacket and pants and they just arrived - super warm and weigh about 11 oz each. just unbelievable. Gives me a load of layering options I didn't have with fleece alone.

Enjoy Kili - I can't wait.

May 22, 2018
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