Combining Two Sleeping Bags

[Furry]

Can anyone provide input on using two sleeping bags (one inside the other) to get a lower temp. rating than the two bags by themselves? I've got a 20-degree down bag and a 0-degree synthetic bag (it's actually probably about a 20-degree rating since it's relatively old and has been compressed so much). I was wondering what the rating could, in theory, be if the two were used together. Does anyone have experience doing this?

 

[Rick]

I have done this for my wife before I bought her a -20 Down bag. She is realtively small 5'6" 110lbs. and wouldn't really compress insulation.
I used a 40d summer down bag inside a 20d MH crazy legs down bag. She was comfy down to about +5.

However, I would caution that if you are of average size, you might set yourself up for failure by compressing either the down on the inner bag or the synth of the outer bag (or the reverse, if you use the down outside). There is only so much room in a bag and the only way to exceed that room is to compress the fill - and for the most part it is the height of the fill that insulates you and slows your heat loss.. Keep in mind that you also don;t have the benefit of a heavier draft tube chest baffle or higher anmount of fill in the toe box, all are places that can cause serious cold spots.

If the synth bag is that old and compressed, I would save it as a carbag or pet pillow and invest in another bag. There are a lot around that seem pretty cheap right now.

 

[Bluethroatedone]

You can always drape bag 2 over/around you....

 

[bubba]

I bought a fleece liner and it really made a difference for me (even if you double bag it would give another gentle layer). I've also used hand/body warmers to warm the bag and me. It's great!

 

[DougPaul]

This topic has been discussed before.

The warmth of two bags can be estimated by measuring the total loft. See my posts in the thread "Sleeping Bag Ratings?" http://www.vftt.org/forums/showthread.php?t=6164

More useful info in the thread "Layering Sleeping Bags"
http://www.vftt.org/forums/showthread.php?t=9776&highlight=sleeping

A true winter sleeping bag will also have special features such as a draft collar.

Doug

 

[Chip]

I bought a fleece liner and it really made a difference for me (even if you double bag it would give another gentle layer)...It's great!

I agree about the fleece. I'm sure it adds a full 10 to 15 degrees to my spring bag's rating AND you get that psychologically warm fuzzy feeling as an added benefit . This is a $15 fleece "sleeping bag" from walmart.

 

[Nessmuk]

I bought a fleece liner and it really made a difference for me (even if you double bag it would give another gentle layer). I've also used hand/body warmers to warm the bag and me. It's great!

Fleece liner in cool weather, silk in summer... I wouldn't be without them. Keeps your bag clean, adds warmth (even the thin silk adds a lot), gives you temp control options. Either is well worth the additional weight in any season.

 

[TomD]

Overbag

I have a MacPac -5C bag and an MEC overbag that is designed for this purpose-it is supposed to add about 7-8C to the bag rating. I also have a Bibler Winter Bivy. Climbing into this combo is a bit tricky-the MacPac has a full zip, but the MEC has only a half zip and the Bibler only a cross chest zip. I have used this combo in Yosemite, but not sure how cold it was-probably around 20F. I'm a cold sleeper and it was toasty. As already discussed, the secret is an overbag that doesn't compress the inner bag so that you don't lose the inner bag's loft.

 

[Mike P.]

I have an overbag also, untested in the field for it's intended use, I more often use it by itself or with cotten liner for over 50 degree nights or places like Lyons. Supposed to add 10-15 degrees warmth.

I got it the idea I would add to 20 degree bag for winter camping on a selected weekend in CT when below zero is unlikely & don't mess up as badly in temp guessimates in the weather forecast.

 

[Mad Townie]

Before I got my winter bag I used a +20 Bean's down bag with an EMS "Polar Outer". Worked fine in the Maine mountains for many years, temps down to at least 0. If I got cold I'd put on some clothing. No problems.

 

[jbrown]

I considered doing just this last year when I was planning on overnighting at Marcy Dam when doing Marcy. I have a 40 degree bag from Lafuma that has a very narrow cut, and my brother has a 25 degree bag from Kelty that is a very wide cut. (Both are synthetic, by the way.) I wanted to test the rating of one inside the other before venturing out in the winter, though.

I've had good results with just a 1/2 sleeping pad, fleece blanket and my trekking tarp down into the lower 40's, and I've used a crappy old synthetic car camping bag (no known rating) down into the teens, so I'm not that worried about getting cold...

I'd be interested in hearing about the results of the experiment.

 

[sleeping bear]

I use two bags for winter as well. I've got a 20 degree synthetic kelty and a converted down bag (half of an old rectangular EB bag with light polyester sewn to the other side and a half zip). I've used them together down to zero and was soooo toasty! I'm usually a cold sleeper, but I've been down to long underwear and a t-shirt.

I think what one needs to look at is the thickness of the loft, as opposed to degree ratings. My synthic bag has an inch or two, and the down is about 3 or 4. Combined for winter I've got 5 or 6 inches (on the top anyway) and that seems to be suffiecient for me.

In comparisson, I've also got a Wiggy's brand 0 degree synthetic bag that I freeze in. It think it's loft is about 3, maybe 4 inches. It also has a very pathetic excuse for a draft collar

 

[Lawn Sale]

I have a sleeping bag expander for my 0° synthetic that works well. I put the 15° down inside it and it's good to well below zero. I've thought about the -40° bags, but until I find one at a lawn sale, this will have to do...