Doubling up on bags?

I would be careful doubling up sleeping bags if both are deployed as sleeping bags (fully zipped up). Unless the outer bag is quite large you'll get significant insulation compression. I have done this using a MYOG bag expander for the outer bag … worked OK warmthwise but was a pain dealing with multiple zippers and keeping the breathing holes line up.

I have also doubled quilts … one that keeps me warm at 40F and another that is good in the upper 20's. That combo left me lightly chilled slightly below 0F, but I may have had enough pad insulation (definitely less than the R5 recommended by RN Labs). Will be doing backyard testing of that combo with one of Bender's R9 GoosePads as soon as we get nights solidly below 0F.

I have also used the two quilts as an "top bag" over a sleeping bag rated to 30F (Marmot Arroyo) and was toast warm at -13F.

All of the above experience was under a 5×8 tarp. The -13F night was also in a bivy sack not zipped completely (face area open).

What about one of the Jacks R Better quilts that open flat. A summer-weight one could work.

I had experience last winter using two bags with a total of 20 oz of 750-fill down, each with a 64 inch chest girth. I actually found that there wasn't much down compression, but instead that it expanded to fill in all of the empty spaces inside the bag. I slept a few nights using this setup in temps down to 10 F and was always toasty warm. I will continue with this setup this winter as I can't afford a nice winter bag and this seems to work fine.

I had a similar issue and decided on a synthetic overbag. It prevents the draft issue, adds considerable warmth, and works well ensuring minimal moisture in my sleeping bag.

This is the one I have been using:

http://www.mec.ca/AST/ShopMEC/HikingCamping/SleepingBags/PRD~5021-089/mec-amulet-ultralight-overbag.jsp

I have a Mountain Hardware Polarguard Delta -20 F. bag that has a parallel zipper that opens a 6" gore in this bag. I've tried the bag with the gore opened with my WM Megalite bag inside and it fits well, with no significant compression of the down.

This is a great combination if I ever camp in severe winter weather because my body moisture will migrate through the inner down bag and some will condense inside the outer layer of the synthetic bag. But I'd likely be using a VBL bag inside the down bag so moisture would be no issue except for frost from respiration on the outer bag's shell.

Piper I have done just that. I have a Go Lite Ultra 20 also and I have use it in conjunction with my JRB Stealth (40º quilt no longer made) in my hammock down to 2º. Was warm and toasty and I'm cold natured. I used the JRB over the Go Lite as it is larger.

I just did my first winter campout this past February and slept outside in several combinations of sleeping systems before I went out on the trip.

I used a Columbia fleece blanket inside a Mountain Smith mummy bag rated for -10. Also used a Sea-to-summit bag liner and an Outdoors Products fleece sleeping bag from Wal-Mart. Tried all of them at once was smothered.

The combination I used on the trip was the mummy bag and the Columbia blanket. temperatures were in the low teens at night. I also use a bivvy shell which is windproof and waterproof and traps some of the heat lost through the sleeping bag. Lightweight and pretty comfortable.

Lots of options. That outer bag thing was an interesting system. I didn't realize there was a tactical purpose for something like this. It seemed a little heavy for a single-purpose item, though. Maybe if I was camping in Canada.

generally overbags are recommended to be synth for the condensation and dew point issues david has elaborated on and experienced first hand

also generally calculate that a 40F or so summer bag/quilt will add ~15-20F to the rating

…

Sue and I each have UL summer quilts weighing about 700 gm. Fine in summer, except for a few times in the mountains when it has gone way sub-zero. Then we snuggle up and layer one quilt on top of another. Been warm down to -7 C that way.

In winter I have used those same summer quilts with an widish over-quilt on top. That worked fine too.

What I would not try to do is put one stock SB inside another stock SB. There isn't enough volume for all the down to fluff up. Quilt over SB works of course, and custom (=large) overbag works too.

Don't forget your head insulation too!

Cheers

I have been thinking along the same lines as you Piper. I currently use a Jacks R Better quilt that doesn't quite do the job for me when the temperatures drop. I'm looking closely at MLD Spirit quilts as a top layer. The synthetic insulation removes some of the condensation worries, and I like it that the insulation is a continuous long staple, and therefore unlikely to shift. This has always been problematic for me with down bags and quilts.

I took the plunge and ordered a summer-weight Jacks-R-Better wearable quilt. It opens up flat so I ought to be able to use it like a blanket inside my Golite quilt. There ought to be enough room since I'm able to wear jackets and down pants inside the quilt. I just won't need to do that anymore. Heck, with the wearable nature of the quilt, maybe I can double-up over or under my down sweater and thus have no need for a warmer jacket. I still have to see how practical the wearable quilt idea is.

I should have also mentioned in my previous post that Eric and Roger were most helpful recently and it is one of the reasons I went with the synthetic overbag. As a quilt user, I do like how it also minimizes drafts (like a really large bivy) and the benefits with respect to moisture management are well documented.

So thanks again Eric & Roger.

@Diane – looking forward to your review of the JRB!