Combining sleeping bags for greater warmth

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adirobdack46r

adirobdack46r

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Is there any sort of formula for the temperature rating one would expect when using more than one sleeping bag? Like what happens to the temp rating if you add a fleece sleeping bag in to another bag? Or I have a 45-degree ultralight synthetic bag that is so small and light it is like packing nothing at all. Is there any way of guesstimating in what temps I’d be comfortable in if I put another one inside the one I have?
 
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Combining layers of insulation has successively diminishing returns as you'll eventually compress your best layer. Here's some crib notes based on my experience (fwiw);
- Fleece liners add about 10 degrees and a comfort factor but are bulky.
- silk liners add about 10 degrees, are compact and light but tend to be tricky to manage getting in and out of the bag.
- An inexpensive nylon bag shell or bivvy adds about 10 degrees, keeps your bag clean and keeps you, your bag and pads in the same place.

If you combined all 3 of these, I'm confident you would not get 30 degrees more rating.

I carry a VBL for emergencies but have never slept in it.
 
adirobdack46r said:
Seeing as VBs were just mentioned, has anyone ever tried out such a concept as this?

http://www.backpacking.net/makegear/falk-sleepbag/index.html

Basicaly you are talking about a heat reflective VB with a fleece liner in it. I wonder what sort of temps a person could be warm in.
Click to expand...
You and your insulation will get soaked in this arrangement.

The VB has to be on the warm side of the insulation or you will get condensation on the inside.

See Dave.M's page on VBLs for more info: http://home.comcast.net/~pinnah/DirtbagPinner/vb.txt

I personally wouldn't consider one unless it is below 0F or so and then it goes inside a winter sleeping bag.

Doug
 
I sort of figured that any insulation inside the VB would get soaked rendering it useless but I thought perhaps those that put things out there on the internet might know something I didn't. Often times probably so, but doesn't look like that's the case this time.
 
Ive put a 40 degree inside a 20 degree,both synthetic, and was toasty at about -5. Used a solid core and self inflater. Heavy but worked. I usually just rent a -20 or -40 at ems for the couple of weekends in feb and march that my 0 is not up to. Check out the Stephenson's Warmlite site - its a hoot.
 
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