Combining two down bags for warmth

[Bill Reynolds]

Was curious how efficient combining my 40 degree Golite long quilt (340 grams fill weight ) and my Western Mountaineering Megalite long(13oz fill weight)into one sleep system for Winter. The quilt fits quite nicely over the Megalite without compressing the down.I already have an old 775 fill winter bag with 28 oz fill but it weighs 3 lb 10 oz whereas the combo would only weigh 2 lbs 15oz. I know there would be a small hastle to deal with two bags but my gut tells me this combo may even be warmer since some air would get trapped between the two. Does anyone out there have any experience with a setup like this?

[Franco Darioli]

I thought about doing that (many have and some do..) but after a few test at home I came to the conclusion that I prefer to wear my puffy down clothing (pants and hooded jacket) on top of my merino baselayer instead of the double bag.
I have the puffy clothing as dedicated camp layers (that is I don't sweat in them) so I save weight and space that way.
The bonus point for me is that now I don't wait half an hour after waking up to decide to go out for a pee…
To explain my temperature range, using the Summerlite plus WM Flash pants and jacket gives me a similar warmth level to using an Ultralite , the total amount of down is about the same.
Both take me down to around 20f. (on top of a good mat…)

[Raymond Estrella]

I just did it last Thursday. We had a storm coming in and my son wanted to spend the night in it so I set up a new shelter outside the living room window so my daughter could "see" us. I put my son in his 20 F SD bag and put a JRB Sierra Stealth quilt on top, sticking the foot of the bag into the footbox of the quilt. It got down to 13 F that night and he said he was too hot a couple times. Here is a shot of us when we turned in. (He wanted my down hood and started with it on, but quickly shed it.)

Here is a shot of the tent, a Brooks Range Propel right before I dug out the entry at bed time.

This winter I am going to do quite a bit of experimenting with doubling quilts or mixing quilts with bags like I did with Raymond. Hopefully I will have better/more examples later in the winter.

[Steven McAllister]

A few people have reported good results layering bags/quilts.

There are even some military 4 season systems where soldiers are given a summer bag and a corner season bag. Both are combined to create their cold winter bedding.

I guess when they get called on a mission, they take what they need depending on the climate.

I know I don't have a winter bag and have combined a 40 degF bag with a 30 degF bag plus extra fluffy clothing to be pefectly warm down to 10 degF and below.

I think a good way to calculate is to measure the layers and compare to a single winter bag or quilt. It's all in the combined loft fo you bag/quilt and clothing.

One thing that has been proven, and what I have personally found, is that a better weight to warmth ration can be attained if you focus on your core, neck and head area. So a thick puffy vest and warm hood/balaclava/hat is more important than puffy sleeves and leg insulation.

[Bill Reynolds]

Thanks Raymond that is a great shot.

[Richard Lyon]

I've done it, and in fact bought an overbag for that purpose, see http://www.backpackgeartest.org/reviews/Sleep%20Gear/Sleeping%20Bags/Feathered%20Friends%20Great%20Auk%20Sleeping%20Bag/Owner%20Review%20by%20Richard%20Lyon/

Works OK, and for a cold sleeper like me is far preferable to augmenting a bag with a down sweater. I need that sweater anyway!

A bag and an overbag weigh more than a quality expedition bag. If you go out in arctic conditions often, I'd go for the expedition bag.

Richard

[Franco Darioli]

On this theme, something I would be interested to know if anyone has used a synthetic quilt on top of a down bag.
That was the reason why I bought a quilt to see if I could transfer the dampness in my footbox (not from touching the walls) to the quilt.
Not a problem for me because I only spend 1-3 nights on snow at a time (and I have VB socks,but only use them for 30 min or so…) but just in case I wanted to stay out longer…
(after I bought the quilt I opted for the puffy layer option )

[Raymond Estrella]

Hola, Ricardo, mi amigo. ;-)

I learned that I need to use tinyURL for the links here as it blows the page up. Some day I need to learn how some of us embed the link. I can't see a way, but I am thick. (And not just in the middle..)

[Raymond Estrella]

“A bag and an overbag weigh more than a quality expedition bag.”

This is absolutely true. And if you plan to spend much time at extreme low temps I highly recommend a very good sleeping bag. Back in 2004 and 05 I played with true over-bag systems and decided it was just too heavy. (Plus you really need to remember what side your zippers are on when buying bags. ;-)

Discovering quilts changed things a bit.

These days I give myself projects just to have something to do when hiking. This year’s winter project is to try building a two-part sleeping system with a wide temperature spread of possible use. Since it will take place in winter and spring (which is pretty darn cold here too) I am going to look at a 0 F bag and a 35 F quilt. My thinking is that with venting the bag, spreading the quilt, and doubling when needed I may be able to have a sleep system that can be used at a temp range from 45 to 50 F to a low of -15 to -20 F. I am not doing it with two quilts as I am trying to find something that works for a wide spread of users. (I do plan on doing some personal double quilt trips too.)

Sorry Franco, I plan on using down.

[M B]

i can fit my 40f down quilt inside my megalite with me.
there is room without compressing the quilt much at all if any, since the megalite is quite capacious.
Im comfortable in the megalite with down shifted on top down to mid 20s easily. (my lowest was 22) With the quilt, I think it would approach the single digits.

the combined wt is 25+16=41 oz. Not bad, but still 8oz or so extra fabric wt compared to a single bag, and about a whole lb compared to a single quilt.

[Sam Farrington]

It was explained recently by Greg M. at: http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=16539

I tried it, and found it works on short url's only.

Earlier, Nia S. directed us to tinyurl.com, which shortens them up, and allows a link to their site to go on your tool bar. I wonder how she is doing with that Epic Malibu I sold her for a snow suit.

With the arthritis in the fingers, it is easier to just patch it in, and let the reader do likewise if interested. Just a few keystrokes for both of us, not much to it.

Whilst you guys are out there in the drifts, I am sitting by the wood stove playing the guitar to keep the fingers nimble. Hope you are enjoying it (the drifts, not the guitar playing).

[Richard Lyon]

Sorry team, tinyurls from now on.

Richard

[spelt with a t]

Wouldn't it make more sense to have the synthetic on the inside to better handle water vapor coming off the body?

[rOg w]

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[peter tooke]

newbie to winter camping here, i know nothing but …
Was your second bag down or synthetic?
I already have a summer down bag would love to save money and just use it to add warmth to my WM Kodiak for some planned winter expeditions ( i'm a cold sleeper…). But from some posts on the subject I've searched on this site, many recommend if not insist on putting a synthetic layer on top for precisely that reason, ie moisture build up. So the synthetic overbag layer gets the moisture build up instead of the inner down bag. Keeps its loft, dries out faster given the chance, etc.

Advice?

[rOg w]

deleted

[Paul Ashton]

please remember that you must add incompressible insulation underneath you as well as additional down layers on top. An extra 1/2 inch of CCF foam is one of the best (also easy, light weight, and very inexpensive)ways of improving ones winter sleep system.

[James holden]

synth on the outside … the moisture will migrate to the outer bag, and not get your down too damp …

if you use solely down, there is a good chance your outer bag will become damp, which with down can be an issue

in general an additional 40F summer bag will add about 20F to the rating of the main bag …

[Mike R]

From a bulk and weight point of view, I can't imagine why you'd ever want combine two sleeping bags to make a warmer bag. If you're a very occasional winter tripper then I could understand wanting to save money. I do have a winter sleeping bag, BUT if I didn't, I'd personally consider wearing my insulated pants and parka inside my sleeping bag. You're going to be carrying that stuff anyway. Having insulation tucked into all your nooks and crannies would be very efficient especially when inside your lighter summer weight bag. If you're heading out for any longer than 2-3 nights, you'll want a VBL – companies like WM make some with reflective material which will add more warmth as well. As mentioned above, all this is useless if you don't have a decent mat to sleep on. If winter tripping becomes a common pass time for you, then I'd definitely get a winter weight bag. Get a used one and wash it carefully. Often people buy them for one or two trips.

[Bill Reynolds]

I am the original poster. Thanks for all the responses. If you read my post you'll see that I was just experimenting with some existing equipment. In an ideal world I wouldn't combine bags but use one expedition bag. It just so happens that for me and given the weight of my expedition bag, this combination may be a viable option. Now I only wish my quilt wasn't down although I still think it will work ok. Of course in any option you need sufficient insulation underneath you.

[James holden]

From a bulk and weight point of view, I can't imagine why you'd ever want combine two sleeping bags to make a warmer bag.

because if your on a budget and its what you have … going out and using a system that works but is a pound or so heavier beats sitting on the couch, eating cheezy poofs and doing virtual gear testing on BPL anyday ;)

its that simple …

[Michael Cheifetz]

+1 (AKA "Like" to Eric on the couch sitting but

RE OP – I'm not sure a single bag is ALWAYS best even if you have limitless budget. Some people (eg andy kirkpatrick http://www.andy-kirkpatrick.com/articles/view/double_up) swear by it due to the humidity in the synth thingi

Mike

[Mary D]

+2 on agreeing with Eric!

I use a vapor barrier when it's below freezing, which solves the moisture problem–might be worth considering. It's just my rain gear (I use non-breathable raingear, though).

Consider testing the combo close to your car, so you can bail out to the heater if it doesn't work.

[Martin RJ Carpenter]

PHD (in the UK) have done a few down combis bag for a bit now. They're just standard ones cut a little bit wider/longer and there isn't any clear reason that a quilt should do the same job fairly well.

Their basic pitch for their main series is that you have that and a very light summer bag, use the very light bag in Summer, the combi in Spring/Autumn and the pair in winter. As well as the cost the whole thing is very pleasingly 'tidy' from a conceptual point of view. The 'cost' seems to be ~100g in Autumn/Spring (wider bag so heavier) and maybe 200-250g in winter. Seems a very reasonable trade off to me.

They also do a combi bag for their very warm series so with two data points can get a, very rough!, ball park figure for combination. The ultralight series is +5,-5 individually and -15 when combined. The warmer stuff is -9 and -6 going together to -33. These are rough figures of course, but they'll be honest estimates.

The combination rule seems to be something like combined difference from +16 :) That's with two bags fitting perfectly together of course. Even a quilt over a normal bag probably won't be quite as effective overall and two normal bags might be a lot worse.

[Max Dilthey]

I am a frequent outdoor camper in the winter, but only in the Northeast, where below zero is less common.

So, I think I'm going to try to augment my EMS Solstice 20º with a TNF Aleutian 55º and see how it works. I want the Aleutian for the summer anyways, since it weighs very little in comparison to bags that cost more than 2x as much

($80 Aleutian weighs 1lb 12oz versus the $210 Sierra Designs Wicked Hot 1lb 10oz. The Wicked Hot is 45º instead of 55º but I bet the difference is negligible enough, since the TNF one has a hood and is less roomy.)

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