Using a sleeping bag as a liner?

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Using a sleeping bag as a liner?

Postby atalarico » Thu Oct 04, 2012 8:42 pm

Hey all,

So, I'm having a hard time phrasing my search parameters right, as I'm getting no results for this question.

Basically, does anyone have any experience or thoughts on using my lightweight down summer sleeping bag (REI Kilo Flash +40) as a liner inside of my almost four season bag (Marmot women's Helium +15) in order to make a winter rated bag? The Kilo Flash is 1.2lbs and the women's Helium is 2.1lbs. All told, that's 3.3lbs for what I will estimate as a zero or negative degree high-fill down bag.

I have Cocoon silk liners, a Cocoon Coolmax liner, and a Sea To Summit Reactor Plus liner. I think the Reactor Plus (or the Extreme) would be warm enough for most average winter nights in the high country, but I'm trying to think of the truly bitter cold negatives that this bag-in-a-bag system would work for.

Here's my rationale for owning the women's bag. I'm a male, and I sleep a little warmer like most males. I bought the women's Helium for a few reasons. I'm 5'4" and a regular women's bag is 5'6". The EN rating for a male in the women's bag is 5F. So, I'm not carrying unnecessary weight (regular men's bags are 6' long), I have room for my boot liners and a water bottle inside, and it's going to be a very warm bag.

Is there any downside (pun intended) that I'm not thinking of for this system? I'm going to give it a shot this winter for a few mock expedition style trips to climb Kelso Ridge, Long's, and as many more as I can stand.

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Re: Using a sleeping bag as a liner?

Postby Greenhouseguy » Thu Oct 04, 2012 9:05 pm

The U.S. military uses a light bag inside a heavy bag inside a gore-tex bivy sack for extreme low temperatures:
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Re: Using a sleeping bag as a liner?

Postby MtnClimber82 » Thu Oct 04, 2012 9:08 pm

I used this system as a kid. My kids sleeping bag inside my dad's summer down bag. Worked pretty well.

However the problem you'll likely have is you need an oversized outer bag to fit your inner bag inside otherwise you are just compressing all of your insulation and losing warmth. If you measured the girth of your inner bag all poofed up with you inside it, that is the INSIDE diameter you'd need for your 3+season bag. Most colder weather bags are a snug fit to start with to minimize extra space you have to warm up so I doubt this would work.

Give it a shot in your backyard when it cools down before you take it too the high county.

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Re: Using a sleeping bag as a liner?

Postby kimo » Thu Oct 04, 2012 9:09 pm

I've combined two 20-degree bags in mild winter temps (low teens?) and slept fine. The inner bag gets compressed a bit and I'm sure that hurts the warmth of the system. It took a few nights to be convinced a proper winter bag is the better solution. But yea, no harm in giving the dual bag system a shot outside. Don't think I'd go for bitter cold negatives the first time around. Carry a warm jacket to sleep in. Or don't stray too far from the car.

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Re: Using a sleeping bag as a liner?

Postby Dave B » Thu Oct 04, 2012 9:31 pm

atalarico wrote:The Kilo Flash is 1.2lbs and the women's Helium is 2.1lbs. All told, that's 3.3lbs for what I will estimate as a zero or negative degree high-fill down bag.


It's better to compare fill weights to see how they add up. My wife used a similar system on Aconcagua but with a MontBell spiral down zero and a 40, the combined fill weight of these two bags was the same as the Mont Bell -20 bag, but weighed close to a pound more.

It's situations like Aconcagua where I see a real strength to this system (i.e. warm approach to near-arctic conditions up high), however in winter CO settings I can't help but thing a solid single winter weight bag is going to be better. It'll certainly do in a pinch, but (I think I remember you mentioning being an REI employee) the -20 REI bag seems pretty sweet.
The mountains - whose summits reach or exceed arbitrary thresholds for elevation and prominence - are calling and I must go.

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Re: Using a sleeping bag as a liner?

Postby atalarico » Thu Oct 04, 2012 9:36 pm

Ah! This is exactly why I asked. I hadn't even considered the compression of the loft of which ever bag goes inside. I wonder, if I were to put the smaller big inside the bigger bag, would that mitigate this effect?

I'd love to ante up for a proper winter mountaineering bag, but despite working as a grunt in the "industry" and having discounts for gear, it's tough to afford given the piss poor wages.

Thanks for the brainstorming session! I'll give it a test somewhere reasonably safe to see how it goes.


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Re: Using a sleeping bag as a liner?

Postby GregMiller » Thu Oct 04, 2012 9:49 pm

I actually prefer this method, because it gives you more room to stick stuff to dry out and/or keep warm overnight, like boots/liners, socks, clothing, etc. I put my boots within the outer bag, and I don't have to worry about them freezing, but they're also not getting in my way in the inner bag. Outer layers go between the bags, and base and mid layers go in the inner bag where they stay the warmest.
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Re: Using a sleeping bag as a liner?

Postby TallGrass » Thu Oct 04, 2012 10:25 pm

FWIW, Woot has a High Peak Sirius Sleeping Bag 2 Pack (two 860g/1.9lb 50° mummy bags that can zip together) today (Friday) for $19.99 + $5 shipping. I picked up a pair recently and they will compress down to the strap limits of the "Small" compression sack I have and then some. Might be good for summer, car camping, kids in the backyard, or a liner bag. For $12.50ea, not a bad deal. Picked them up to replace my old summer bag and for reinforcement for my Phantom 32F (800fill).

As they can siamese together, does snuggling lower the temp rating? \:D/ Or does your S.O. suck so much heat that it'd raise it? :?

Woot also has a Kelty 45 Degree Youth Sleeping Bag for $11.99 and you can combine shipping.
Not sure if I'll do more 14ers. The trip reports are too tiring. :wink:

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Re: Using a sleeping bag as a liner?

Postby hotrod » Fri Oct 05, 2012 8:20 am

I used the double bag system for years, down to minus thirties, and it worked beautifully. The only problem I had was having two hoods. The inner one did not fit well into the outer one, and all those drawstrings got confusing. Since the inner bag was an old one, I cut off the hood, fitted the raw edge with a drawstring, and that solved the problem. However, you probably wouldn't want to mutilate a still useful bag.
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Re: Using a sleeping bag as a liner?

Postby mtnjim » Fri Oct 05, 2012 8:31 am

On my first trip out of the country, to Aconcagua, many years ago (1993) I took my North Face Superlight +5f rated bag and my Alpine Designs summer bag (I believe that bag was actually sewn in Boulder!). Because of the snug fit of the North Face bag, I used the Alpine Designs as the outer bag. It worked ok but was still not quite enough at high camp.

Later, I tried using a 0f rated bag as a base camp bag for high altitude expeditions. I sleep cold so it wasn't enough and on my next trip I took a very lightweight down liner bag (Chinook? it was cheap and i was on a budget) to add some warmth. I first tried it as a liner bag since that's what it was listed as and when that didn't quite do it, i took it out and draped it over the heavier bag, not zipping the upper portion and that combo allowed both bags to loft and was definitely warmer. This also allowed me to add a Cocoon flannel liner for more warmth on the next trip.

So my suggestion would be to try the summer bag as a liner and then as a cover to see which combo allows the most loft and warmth. The downside of the bag combo is that it will be heavier than a single bag of equal warmth.


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Re: Using a sleeping bag as a liner?

Postby MuchosPixels » Fri Oct 05, 2012 9:07 am

I also have the Marmot Helium and its a VERY warm bag true to at least its 15F rating.

Its certainly very usable in winter inside a tent.

Before carrying another sleeping bag I would just bring down booties and extra layers. Stuff thats usable not just for sleeping but for around camp.

The sleeping pad makes a huge difference also. A warm, wide pad increases sleeping comfort significantly.

The dual sleeping bag solution works obviously and it helps in reducing the draftiness of any bag. But I prefer the single bag solution and just sleeping with more layers. Layers I anyway need as soon as I get out of the bag.

I like to just get out of the bag, put on my down parka, boots and go.

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Re: Using a sleeping bag as a liner?

Postby RosieTheSummiter » Fri Oct 05, 2012 11:16 am

I camped at the Sand Dunes one year with a 15 degree bag and froze like crazy when it got down to 29 degrees - learned my lesson on the limitations of my bag. Later in the season I rented a 0 degree bag from REI and was profoundly impressed by how warm it was on a cold night at 11,000 ft. A few weeks later, I bought a 0 degree bag, encouraged by what the folks told me at the store about all the research having been redone to finally get the technology correct to account for men's interpretations on warmth vs. women's interpretations. I was hoping it would be just as warm and toasty as the one I rented previously. I then took it to Crestone for fall camping where it got down to just around freezing, and I was so cold I had to sleep in the comparitively warmer car. That new bag was returned to the store the next day. My friend then enlightened me on the trick about lining a sleeping bag with a fleece blanket. I tried this once and was immediately sold on the concept. It cost me $4 from Big Lots and far outdoes my $60 silk sleeping bag liner and anything else I've tried. I'm not sure if it would suffice in pure winter camping conditions, but it might be a nice supplement to what you have.
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