Layering Sleeping Bags?

[Chad Miller]

I am hoping some of you can help me out with a bag layering question.

I have had several people tell me that I should look at using an over bag or a quilt to increase my current bags rating. I was looking at using the following two bags for winter backpacking:

Big Agnes Yampa (10.5 oz. of 850 goose down)
MontBell UL Stretch Down Hugger #3 (11 oz. of 800 goose down).

The Big Agnes website generously states that the Yampa with add 25 degrees to your base bag. I know this is simply a general temperature rating but I wanted to get other peoples options on the matter.

Question #1
How accurate do you think BA claim of adding 25 degrees is? I am a bit skeptical of the claim due to the following;

1. The UL #3 has no draft collar
2. The Yamp has no hood.
3. Will 21.5 oz. of down really keep me warm down to 5 degrees?

I know that one of the best ways to gauge a bags temperature rating is by measuring the weight or thickness of the down in the bag. Unfortunately I cannot seem to find the figures detail the general weight / thickness to temperature ratings.

Question #2
Could someone please point in the right direction for data on thickness / weight of down compared to temperature ratings?

[P. P.]

I have no experience with the Big Agnes mentioned.
The JRB website shows these temperature ratings with their respective inches of loft:
Comfort Rating (°F) = Loft (inches)
40 = 1.5
30 = 2.0
20 = 2.5
10 = 3.25
0 = 4.0

How it helps. I use a quilt to augment my 0* bag but haven't gotten scientific about it yet.

[Laurie Ann March]

while I can't comment on the gear you mentioned here is my experience with several down bags (800 to 850 fill) and a range of ratings between -7ºC to -10ºC. I find that the bags get too cool and that the ratings would be more accurate as -5ºC to -8ºC.

Keep in mind that everyone is a little different and that women tend to need more warmth in some areas than men. This is just my take on it.

This said I have a synthetic and down combination bag from Marmot I think (I'd have to go look). While it doesn't pack as light or compact – I find the temperature rating on it much more accurate.

[Richard Matthews]

My concern when layering is that the overbag is wide enough to reach the ground on both sides and that the inside bag will not be compressed by the overbag.

I have a Big Agnes Cross Mountain and it does compress the inside bag. I wear a 48" regular coat.

The draft collar and hood do not work well for side sleepers. I prefer a balaclava.

[Chad Miller]

Thanks for the information so far.

The Yampa is suppose to be intended as an over bag. It has the standard BA design where you slide the sleeping pad into a sleeve on the bottom of the bag.

The Yampas bags dimensions are pretty big, 73inch; shoulder girth, 69 inch; hip/ foot girth.

The MontBell bag dimensions are shoulder girth of 56-75 inches and knee girth of 47-63 inches.

[Michael Davis]

Chad,

I'm glad you started this thread. I have been contemplating a similar move but, with a different approach (though not necessarily better).

I have a Western Mountaineering MegaLite 30'F bag and my tentative plan is to buy a Montbell UL SuperStretch 0'F bag and put the WM bag inside the Montbell to make a sub-zero bag. That would give me quite a range of temps using combinations of just 2 bags.

My theory (hope) is that the Montbell will both expand large enough to not compress the WM bag but at the same time, have enought tension to eliminate the air space between the bags.

Anyone tried this approach?

[Siegmund Beimfohr]

I also am very interested in this two-bag approach. My basic bag has been a Montbell UL SS Down Hugger #3 (32 deg) bag that I've used primarily as a quilt this year so far. I thought that a synthetic quilt would be the ticket for an overbag so ordered the Cocoon Pro 90 quilt. No go (see my review) as it's just way too small to function as an overbag over any reasonable 3-season bag. The new MLD XP Quilt looks like it might be the ideal overbag while still being light enough by itself for summer conditions but I hesitate to spend that much money without confidence that it will work.

As far as doubling two sleeping bags for winter, does anyone know how a lighter bag such as a Montbell UL Alpine Burrow bag #7 will work inside the Super Stretch Down Hugger #3? I am assuming that the stretch system will expand to handle the inner bag but have no experience yet trying this. Unfortunately, this particular combination reverses the desired arrangement of synthetic insulation on the outside to contain evaporated moisture as it cools so that the down stays moisture-free.

Anyone have actual experience nesting one bag inside another or with a quilt that is large enough to serve as an overbag? Specific bag brands/types would be useful information. Thanks.

[john Tier]

FWIW, the JRB Large Family of Quilts functions well as an over quilt or bag in combo with the DTEPC (80 inches of girth)…. Several in cold climates persued this approach last year…. see the fifth function and photo here… http://www.jacksrbetter.com/index_files/Large%20Quilts.htm.

As a co-owner of JRB I may be biased

Pan

[Tommy Clapp]

I use to use 2 Slumberjack Saguaro bags for winter and 1 for summer. it is a 45deg bag but it is heavy for winter. both together weighted 56oz. I used it down to 12deg last winter in a tent and was very warm. I have now gone to a Golite feather(20deg 28oz) and I just ordered a JRB Shenandoah(45deg quilt at 15.5oz) to serve as a summer bag and Overquilt when it is really chilly. I feel like this gives me a good range for all times of the year.

Tommy

[Richard Matthews]

Ok, I will pimp for Jacks'R'Better.

What I have tried that did not work:

Big Agnes Zirkel inside a Big Agnes Cross Mountain. I am a side sleeper so my knees and butt would compress the insulation and cause cold spots. Thick pads inside the Big Agnes sleeve use up some of the girth. Great design and concept for a back sleeper.

I wear a 48 regular coat so a 48" quilt is wide enough for a quilt, but not an overquilt.

What has worked:

A Nunatak Arc Alpinist with a down parka overquilt on the foot box and a Jacks'R'Better No Sniveller sideways over the torso.

Last spring I got a Jacks'R'Better large quilt – the Biker quilt that has been discontinued. I used it over the Nunatak Arc Alpinist one night that was below my thermometer minimum of 14 degrees and think it has a lot of potential, but not yet enough experience to review it. However the Arc Alpinist is 55" wide and the Jacks'R'Better is 64" wide and there was NO drafts. The combination had a very luxurious feel.

[Abdulaziz Al-Arfaj]

In the past I have used a mountain hardwear bag expander to increase the width (8 inches, 20.32 cm) of the one of my summer bags so that it will fit over and not compress the loft of the inner bag which is a warmer fall/winter bag depending on the temps. The bag expander is not that light but it does work and you don't have to buy a new sleeping bag.
This system has worked very well for me and you may want to check it out.

[barry hitchcock]

phdesigns.co.uk have just added a down overbag to their range—-site has a description and temperature ratings for single or combinations—regards from uk

[Chad Miller]

I have spoken with the folks at MontBell about using two of their bags to increase the temperature rating. They don't recommend using any of their bags as over bags (especially the Super Stretch) because the bags are designed to cling to the body and this would seriously constrict loft.

They did say that by using on of their bags as the base bag and using a specifically designed over bag or quilt could work just fine.

[John S.]

If Montbell says don't use another sleeping bag inside their bags, it makes me wonder about even a down jacket. I've heard others say it won't compress the down, but I'm suspicious.

[P. P.]

"Anyone have actual experience nesting one bag
inside another or with a quilt that is large
enough to serve as an overbag? Specific bag brands/types would be useful information. Thanks."

I have been using a JRB Mt Rogers quilt over an LLBean 0* down bag and the quilt works well over both our bags, really. It also is nice to have some DWR on top as our bags do not.
I just bought a Mont-bell 0* hugger (800 fill) which I will also use with the quilt.

[Michael Davis]

Chad,

Thank's for that research.

Much appreciated!

[D.H. Bathon]

First off, I'm confused about those JRB website figures. My Western Mountaineering MityLite has a loft of 3" with 12 oz. of 800 down, but its rated to only 40F. Now granted I've slept in it on a 35 degree night near water and I was fine (my head was cold since its not a mummy) but I can still tell you that its rating is nowhere near the 10-20 degree range the JRB numbers are quoting, though I'm assuming you can attribute this to a different type/weight of down.

I am a side sleeper as well so I enjoy the 62" shoulder/ 46" foot girth it provides. Also my WM is a 6'6" bag, which makes it large enough to accomadate my 6' synthetic Mountain Hardwear Lamina 20F bag inside of it, though it doesn't save any weight (combined the two are over 3 lbs…). I would think the Western Mountaineering MityLite would be a good outerbag for someone smaller or with a smaller bag.

Michael D.
If you use the Montbell as an outer bag, won't the elastic on the Montbell compress the inner bags' down and reduce its insulative properties? Just wondering, its a great idea and I like the idea of the elastic for extra movement, thats what made me buy my Western Mtn in the first place, the Mtn HW was just too constrictive.

[P. P.]

D.H. Are you measuring both the top and bottom of your bag together? Remember, with the quilts, it is just the one thickness, the top.

[john Tier]

DH, et al,

Bags loft is typically stated for the bag zipped and laid out and allowed to fully loft…. So… a 3 inch bag is actually a thickness/ loft of 1.5 inches… about 40 degree range…. Quilts are stated as a single side loft.

Pan

[Brett .]

Siegmund,
You asked specifically about the UL#3 and lighter MB bags for layering. I own the #3, and a #7 also. They layer very well with minimal compression of the inner bag which results from the inner baffles of the #3. Ideally one bag with the total down weight of both lighter bags would be warmer, but having two bags such as a 3 and a 7 gives me a system that goes down way colder than I'd ever want to go. For example my 7 ALONE is good down to 0C(32F) in my tent. (wearing a thermawrap layer). Im guessing my 3 would be good down to -10C ambient and -15 layered?

[Tom Clark]

I mentioned in a previous post lately that I used an old Siera Designs down summer bag (40F) inside a WM Alpinelite (wide version of their 20F down bag) combination during a 2F night. I'm 5'6" and ~160, so there is extra room inside my WM bag alone. I thought it was a great, versatile combination that was better than spending another $300-400 for a 0F bag.

While there might have been some compreession of the bags, the inner bag filled up all of the voids next to me and provided a really good bafle around my neck. When I'm cold, I want everything tucked in around me. I don't know how to do that more efficiently with just a single bag and typical tossing during the night. There is probably a more optimum inner bag for to use, but I already have this other one. I don't know if my combination is more weight efficient than a single 0F bag, but there are other things I could buy with that money I saved.

[William Webber]

Pluses and Minuses of Overbags and Other “Bag Warming” Alternatives

There are several ways to extend/reduce the temperature range of your “basic” or “core” sleeping system:

In Hot Weather:

Pull the hood off your head if you are using a mummy bag; unzip the bag partially; stick your feet out with designs that permit this; unzip the bag completely and use it as a quilt. OR just use a quilt which allows a lot of these variations on the fly (by wiggling around and shrugging). Skip a tent, use a bug net over your head (tents are notoriously hot and muggy in the summer). Use a tarp if rain is a possibility. Adjust the amount of clothing based on the temperature (take off clothing and sleep in base layer – to keep the bag clean). Once again a quilt is useful because you can go to sleep in your trail clothing (or switch to your alternate set, if your trail clothing needs to dry out. I like to have the stuff in my pockets and feel naked if – I am, well, naked or just in base layer.

In Cold Weather:

Add a tent. Nothing keeps a secondary envelope of warmer air around you like a tent.

Add a bivvy sack. The secondary envelope of warmer air isn’t as great as with a tent, but it’s better than just the sleeping bag.

Add vapor barrier layers. This is especially important if you are going to be in a tent or bivvy sack, since otherwise moisture will accumulate in your sleeping system and reduce its efficiency. Oware used to sell a very light, impermeable emergency bivvy sack that you could wear as an “inner bag liner.” I prefer using my “light” rain gear – Houdini jacket and pants (the original Dragonfly version is REALLY a vapor barrier, but the Houdini builds up a “comfort zone” around your skin while keeping your sleeping system relatively dry). Wear the vapor barrier right over your base layer, which means your clothing will be “inside out” with the jacket and rain pants closer to your skin, and extra clothing on top of them.

Add clothing. Before thinking about an over-bag, think about puffy jackets and puffy pants (I like the Patagonia Micropuff with hood.and their pants). You should be thinking survival – if it’s really nasty, you will probably never have enough layers and overbags to just lie around waiting for rescue, so you have to count on building up therms by moving (hiking out!) and figure out the minimum you need for the coldest, wettest projected or historical weather (or somewhere in that vicinity, depending on your taste for risk). Naturally Primaloft, Thermalite, Polaguard all all superior to down, which can wet out. (If you hike out in worst case scenario, the “light rain” gear goes OVER the puffy layers. There will be some wetting out but probably not enough to impair the insulating layers.)

If you are STILL pushing the limits on your basic bag, ONLY NOW should you think about an overbag. OVERBAGS ARE INHERENTLY INEFFICIENT. You are trading a single, high loft bag with only TWO layers of shell fabric for an EXTRA TWO LAYERS OF SHELL FABRIC, not to mention potential weight additions like zippers.

If you are not a believer in vapor barrier/slow down clothing layers (the ultralight “light rain” clothing), the extra fabric layers are somewhat helpful in preventing humidity soak through/rain soak through, but the only advantage of using two bags is to save money.

My personal preference for the overbag option is to combine a summer weight quilt (which I usually spec in Jardine’s “extra insulation” configuration and a little oversize, since I sleep cold) with an ultralight mummy bag like a Montbell or Western Mountaineering – something around 16-20 ounces. It’s important to spec the quilt oversize so you can tuck it under you (and during the summer it’s adequate for couples camping). It’s also critical to use a bivvy bag (like the Bibler Winter Bivvy, except it runs a little small) to make sure air doesn’t seem under the edges of the quilt, or else to wrap a tarp around you (which traps air, another reason why you need vapor barriers as your first defense). As an alternative, you can purchase elastic bands (an inch or so wide) and sew them into “hoops” to wrap around your quilt over mummy sack.

Finally, check the stats and reports. You need a MASSIVELY thick (relative to ultralight hiking standards) ground pad to keep from losing heat through the ground, and it needs to be long enough to cover your legs – now is not the time to let your legs dangle on cold ground off the pad, or to drape them over “just” your backpack.

[Siegmund Beimfohr]

Brett,

I was hoping you'd weigh in with your thoughts since I know you are very familiar with and use the Montbell products. Although I've been looking at true quilts for stand-alone summer use and as an overbag to my #3 UL SS DH (MLD's new XP quilt looks very interesting), I do have a UL Alpine Burrow bag #7 coming that I will probably use for summer. I've been using the #3 this year, always fully unzipped as a quilt so far, but it's too warm and heavier than necessary.

Specifically on the Burrow bags, do you have any thoughts on the tiled Exceloft insulation of the #7 compared to down? You mentioned owning both a #3 and #7 but didn't say which model although it read like they are both down; I assume you put the 7 inside the 3. How does the Burrow bag compare for bulk (loft) with the equivalent temperature down bag? Interesting that you get 32F out of the #7 with a thermawrap layer (both top and bottom?). I always use light long underwear in my bag to keep the dirt off if nothing else; I would guess with both bags nested there wouldn't be room for anything else without compressing insulation.

I'm also puzzled as to why the SS Burrow #7 Long ($125) is so much cheaper than the UL Alpine Burrow #7 ($164); it would seem that the SS system would be more complicated (it also weighs considerable more).

Synthetic on the outside bag would seem to be the better combination for moisture control, but I'm sure that won't work with the two bags I'll have. Anyway, am interested in any thoughts and experience you have with the different Montbell versions: Down Hugger vs. Burrow, UL vs. regular, SS vs. Alpine, etc.

Thanks, Sig

[Brett .]

Sig, I just saw your post. Ill edit this post with answers tomorrow, sorry; really busy today!

[James Rivet]

I am planning on doing some winter hiking in the San Bernardino Forest, and I am curious to know what people feel is a safe/ light and warm winter bag or quilt for such conditions. I plan on watching the weather so I hope to keep the bag/quilt as dry as possible (Not backpacking in freezing rain and falling snow). Temps. will sometimes be around 15 degrees F. I sleep cold. Any suggestions.

[Author]

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