bivys for added insulation?

10:51 a.m. on February 25, 2003 (EST)
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a.k.a. Kate, solaceseeker

I am new to winter camping in the Cdn. Rockies, and am looking for a relatively lightweight way to increase the temperature rating of my sleeping bag. I have a SD down bag rated to -15C, and being a cold sleeper, I need something to increase the warmth. I already use a Polartec fleece bag liner, and I have heard that adding a bivy will increase warmth greatly. Any comments on this would be appreciated!

Kate

11:48 a.m. on February 25, 2003 (EST)
(Guest)

a.k.a. MattJ, matt_j

I don't think you will be able to see that much of a difference. Bivys are used as element protection not as much as a temperature control units. I own Moutain Hardwear bivy for my bag and that really only protects me from the rain and wetness of the ground. Why don't you try using a second fleece liner? Also a lot of people that complain about their bags being not sufficient are not really taking care of their ground insulation. Just my $0.02.

Matt

1:44 p.m. on February 25, 2003 (EST)
(Guest)

>Why don't you try using a second fleece liner? Also a lot of people that complain about their bags being not sufficient are not really taking care of their ground insulation.<

This could be the real answer for you and not a bivy sack (though I, admitedly, do not use or know much about bivy sacks). What type of pad do you use? Other ideas are to cover your bag with your coat and to put your morning's clothes under your bag as additional layers of insulation(yeah, I know, some people put their clothes in their bag).

2:39 p.m. on February 25, 2003 (EST)
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-15F bag for Can Rockies????

Kate -

That seems a bit skimpy, based on my half dozen nights in the Canadian Rockies in winter. If you meant -15C (+5F), it is even more skimpy, However, as Matt and Paul have indicated, there are a couple things you can do to avoid buying another replacement bag.

1st thing is sleep in a good 4-season tent. A snow shelter is even better, since the temperature inside will be close in the 25 to 40 F range, depending on how many others you have in the shelter.

I assume you will be using long johns (synthetic, wicking, no cotton), probably expedition weight at the lower temperatures.

Bivy sack - adds maybe 5 deg (all these are F), the main benefit being wind and wet protection.

Vapor Barrier Liner - at temperatures from +5F on down, these add about 5F to the warmth, but whether it works for you is very much a personal preference.

Fleece liner - adds 10-20F warmth.

Second sleeping bag in a double-bag setup - a summer-weight synthetic bag (a +40F bag, for example) can take you down to -35 or -40F, but it is bulky and heavy to have this combination.

Your bag should be a fairly close-fitting mummy shape, which is what I would expect a -15F bag to be (can't imagine anyone ever rating a rectangular or even semi-mummy bag as anything below +25F, but then some manufacturers are a bit optimistic).

Most important, at those temperatures, you will probably be on snow (or ice, having slept on a couple of glaciers). As Matt says, the pad is the major insulator. You should have at least the equivalent of an inch of closed cell foam - 2 thicknesses of "blue foam" or RidgeRest. Self-inflatables are ok, but need to be thicker for the same insulation (yeah, yeah, Jimmy will chime in about his down-filled inflatable, and indeed it is very warm and very thick for the weight). All inflatables, though, have a potential problem in that the valves can fail and they can be punctured. So carry at least a single closed cell pad as a backup (it won't deflate, although you will be cool for the rest of the trip).

2:56 p.m. on February 25, 2003 (EST)
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a.k.a. Kate, solaceseeker
-15 C bag for the Rockies...

Thanks for the speedy replies!

The bag I have is a -15 Celsius bag. I have found I have been comfortable to about -12/13 celsius with my bag liner. So if I can figure out a way to add several more degrees of warmth I think I should be okay for a weekend in March (in a quinzee).

I am planning on doubling up on sleeping pads - a Ridge rest and a Therma-rest. Also, I usually end up with my down vest inside my bag.

My concern with getting another bag - or an "add-on" bag like Mtn. Hardwears is the weight. I am a pretty big wimp when it comes to hauling gear (summer = 25 lbs or less for a week). I realize that I will be carrying more for a winter trip but I am hesitant to add another couple pounds if I could add less than a pound for a bivy. That said, if I am not going to feel an increase in warmth, I might as well "suck it up" and go for the additional weight.

Speaking of which - does anyone find a difference in pack weight when on skis rather than foot? I have never gone on a ski trip longer than a day so I am curious to know!

Thanks again!!!

Katie

3:02 p.m. on February 25, 2003 (EST)
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a.k.a. Kate, solaceseeker
one more thing...

Is a bivy worth the weight for keeping my bag dry? My bag has a Pertex shell, but I hate to take the risk of getting wet.

Thanks

6:39 p.m. on February 25, 2003 (EST)
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Re: -15 C bag for the Rockies...

Quote:

The bag I have is a -15 Celsius bag. I have found I have been comfortable to about -12/13 celsius with my bag liner. So if I can figure out a way to add several more degrees of warmth I think I should be okay for a weekend in March (in a quinzee).

In a quinzhee, you should be quite warm in your bag without any additions. As I noted before, temperatures in snow shelters (snow caves, quinzhees, igloos) are typically close to freezing, depending on how many people are in them, even when temperatures outside are down in the -40 range (-40C=-40C, as it turns out). Trench shelters tend to be colder, although if you do a proper cold trap as most people do for the cave/quinzhee/igloo, they can be warm, as well.

Quote:

I am planning on doubling up on sleeping pads - a Ridge rest and a Therma-rest. Also, I usually end up with my down vest inside my bag.

Should be fine. Keep in mind, of course, that warmth is an individual thing, and depends also on factors like fatigue, hydration, food eaten close to bedtime, damp clothing, etc. You will probably find that a change into a dry pair of expedition weight longjohns and getting the damp (sweat or snow dampened) clothes out of the bag helps. Attempting to dry clothes (including socks) by body heat in the bag tends to get the moisture into the bag's insulation, which is very problematic for down, and also reduces synth's insulating capacity.

Quote:

My concern with getting another bag - or an "add-on" bag like Mtn. Hardwears is the weight. I am a pretty big wimp when it comes to hauling gear (summer = 25 lbs or less for a week).

Including food and fuel? Hey, you are in my club! Most people have that much for a one night overnight in the summer.

Quote:

...I realize that I will be carrying more for a winter trip but I am hesitant to add another couple pounds if I could add less than a pound for a bivy. That said, if I am not going to feel an increase in warmth, I might as well "suck it up" and go for the additional weight.

The ID superlight bivies (5 oz for the one I have) do as well as heavier ones in a snow shelter for giving the 3C/5F of added warmth. Sounds like this would be adequate, if you are warm in your bag at -12C

Quote:

Speaking of which - does anyone find a difference in pack weight when on skis rather than foot? I have never gone on a ski trip longer than a day so I am curious to know!

Absolutely! First is the balance question when skiing with a pack. Second is the extra repair stuff you should be carrying, in case of binding problems, etc. Then there are - waxes, skins, the poles, the heavier boots, the skis themselves, ... Lots of considerations.

8:31 a.m. on February 26, 2003 (EST)
(Guest)

Re: one more thing...

Yes I believe it is.
Your sleeping bag is your lifeline, and being down must be kept dry. Plus you can use the bivy sack in the future.
Other things a bivy is useful for - if you roll around keeps you on/near your pad, keeps the bag clean, protects from embers if you`re cooking in or near your tent/shelter, and as mentioned, keeps it dry and adds a bit of warmth.

Also, if you want you could pack your sleeping bag in the bivy for true waterproof protection.
Another possible aspect of sleeping in a snow cave is if there is moisture etc. or a bit of snow falls/whatever on your bag, it melts due to your body heat - or freezes to your bag.

At any rate a good, light (cheap!) bivy sack is a must

10:28 a.m. on February 26, 2003 (EST)
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No insulation in thin shell material...

Quote:

I am new to winter camping in the Cdn. Rockies, and am looking for a relatively lightweight way to increase the temperature rating of my sleeping bag. I have a SD down bag rated to -15C, and being a cold sleeper, I need something to increase the warmth. I already use a Polartec fleece bag liner, and I have heard that adding a bivy will increase warmth greatly. Any comments on this would be appreciated!

My opinion, not really. You need to add insulation, not thin fabric to boost the temperature rating of a sleeping bag.

Quote:

Is a bivy worth the weight for keeping my bag dry? My bag has a Pertex shell, but I hate to take the risk of getting wet.

Do you know if its "Endurance" style Pertex, ie PU coated? Or DWR+? My opinion, your pertex shell will be fine, especially in cold temps. Better to breath and keep your down warm and dry, than not. Pertex is pretty water resistant, and, if PU coated, pretty waterproof.

So, what to do? You need to either add insulation to the inside or outside of your bag.

Integral Designs makes a "Primaliner" that they claim adds 10C to your bag. That "should" be adequate for "most" winter rockies conditions. Really depends where and how high you are going. If the forecast is for -30, you might not want go anyhoo, as it will be kinda miserable. I'd say ditch the fleece liner, as its much less insulation for the space/weight.

(I note that Integral's down bags, the model rated to -20C is their most popular and the one they recommend for winter conditions in NA, so, your -15C is already close, and if you add 10C, should be fine) www.integraldesigns.com

Another option is an insulated overbag. Which also works if your are concerned about your Pertex liner not being adequate. I have an MEC Emperor Penguin Overbag. MEC claims they add 5 to 10C to your bag. I use mine for a lightweight sleeping bag (ie, my "suffer bag"). Awesome piece of gear and would be mucho functional. www.mec.ca.

Skiing with a pack on? Depends on YOU! I like it, much prefered to hiking. But, slow twisting falls will be much more likely to break something (you or your gear). I've never broken a bone hiking with a pack on, but I have skiing with a pack on... So, depends on your ski skills and somewhat on the ski gear you use. An option is one of those plastic kiddie sleds, especially if your pack is over 20kg. You can even wear a pack, lightly loaded with day stuff, and tow the rest in a sled on the snow. Waaaay better than skiing with a heavy pack on, and since your skiing, you'll be breaking trail anyhoo, so towing a narrow profile kiddie sled is money. And they are light, cheap, and easy to rig.

Sounds like fun!

Brian in SLC

1:28 p.m. on February 26, 2003 (EST)

Everyone else's advice has been pretty good... I would add my opinion to the pile by mentioning that if you're already using a good tent or snow shelter, a bivy sack isn't going to impact your temperature rating much.

A couple things that haven't been mentioned:

First - wear a hat to bed. I use a simple stocking cap (not the sweaty one I wore on the ascent!), and it really does influence how warm I sleep.

Second - be careful adding another liner. If the bag and liner you already use are a close fit, adding another layer inside the bag may just compress the down, and give little additional warmth. In this situation, an over bag might have the advantage.

B

2:13 p.m. on February 26, 2003 (EST)
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Re: No insulation in thin shell material...

Brian is almost right. There are a couple of benefits to the bivy. If you are not in a tent or snow shelter, the bivy adds some wind protection. In a tent, it can cut convective cooling somewhat. Since the bivy is a bit loose around the sleeping bag, it can add a little bit of dead air space. These are the things that add up to the 3C/5F added warmth for the bivy. Note that ain't really very much extra warmth. If you need a lot of warmth, the overbag or down or synth liner are a partial answer, although if it is only an occasional winter trip, the fleece liner you have should be adequate. The suggestion of one other poster of wearing a warm cap is important, and I should have made it earlier.

As for the question of keeping the bag dry - One of the problems of a bivy under many conditions is that, in addition to slowing convective flow over the bag, it also slows the outflow of the moist air coming from you (perspiration of about a pint, breathing of another pint or more overnight). Which means that the moisture from you condenses on the inside of the bivy if it is too waterproof (like Goretex), or even freezes. If your snowcave is damp (temperature a bit above freezing because of having lots of people in it, or cooking inside - which is not a good idea for other reasons), the bivy will keep the outside drip (and spills) off the bag, but it still may be wet from the condensation (a VBL will prevent the condensation, since it will vent the moisture around your bag's face hole).

Lots of tradeoffs here.

To add to what Brian said about the sled, if you use a sled with poles, you can actually be more stable on the skis. I made a sled some years back by adding PVC poles to a kiddy sled - total cost about $20 (US, so what is that, $100 Cdn these days? - just kidding, sort of). We do this mod for the Scouts for winter backpacks, since most of them are too small to carry a full winter pack, and since they don't do much winter camping, a full-on winter bag isn't justified (they use the double bag approach, sometimes 2 summer bags nested, some use a 3-season bag with a fleece liner - adds up to lots of weight).

2:52 p.m. on February 26, 2003 (EST)
(Guest)

a.k.a. Kate, solaceseeker
see this is all very confusing...

This whole winter camping "thing" is into another realm of backpacking. As one of the Brians mentioned, adding another fleece liner is going to make my bag too tight. It seems like there are way too many tradeoffs with using a bivy... but it seems like the best option given my choices (and lack of funds to buy a warmer bag, being a student!). Will I be warmer if I add more layers to me rather than to my bag? I already use a hot water bottle, the hat, mittens and the works.

About the sled - would rope work? I realize there may be some problems with down hills, but the terrain we are going on is pretty mild. It seems like having rigid poles may be hard to ski with? (And yes, Bill, $20USD=$100CDN, or so it seems having just returned from the States on Sunday).

Thanks for your continued de-confusing.

Kate

5:38 p.m. on February 26, 2003 (EST)
(Guest)

For Me, Not in the Bag

Quote:

Will I be warmer if I add more layers to me rather than to my bag? I already use a hot water bottle, the hat, mittens and the works.

Kate, with a nod to the superior experience and knowledge of Bill and the Brians, I wanted to relate my recent snow camping experience where we snowshoed in. I had not snow camped before and was also trying to extend the rating of my sleeping bag. As it turns out, I worn too many clothes to bed in an effort to add warmth and I felt claustrophobic all night. It was too tight for me. In combining the statements of Bill and one of the Brians, if your bag is already a good fit for you, additional layers of clothes in the sack may 1) compress the insulation (I have no experience in this) and 2) be too constrictive for you.

In addressing my situtation in the future, I am going to try to add layers to over, under, or both, the sleeping bag, but NOT in the bag with me. I have since used the bag in its normal rating range and had no claustrophia.

Hope this helps.

5:50 p.m. on February 26, 2003 (EST)
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But fun!

Quote:

Will I be warmer if I add more layers to me rather than to my bag? I already use a hot water bottle, the hat, mittens and the works.

Hmmm...I routinely sleep in a parka inside a bivy sack, and quite comfortably. Probably depends how much room you have.

Hot water bottle for feet and one for chest goes a long ways.

Quote:

About the sled - would rope work? I realize there may be some problems with down hills, but the terrain we are going on is pretty mild. It seems like having rigid poles may be hard to ski with?

Yeah, don't let Bill fool ya, when those PVC poles ram up yer behind side, and bust, won't be no fun a'tall. If its gentile ground, just use lightweight webbing. I run a piece of 1" webbing through the slot where my hipbelt goes on my backpack, then clip a carabiner to the webbing on the sled. Perfect.

A PVC truss can be a nice upgrade, though. Especially if it has a cross bar. You can cut two long PVC pieces (the optimum distance will be far enough to not interfere with the ends of your skis plus a bit) and add a short cross piece about the width of your pack. Run cord thru all pieces and in the junctions between the pieces, tie a loop. Clip the loops to the 1" webbing thru the pack's hipbelt slot. Works super (busted my last set, but, hard use). Also, this truss is easy to stack with your skis for transport, as it folds up easy.

Brian in SLC

9:36 p.m. on February 26, 2003 (EST)
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Baby blankets for over shells...

If you are in a tent - I don't think you said you were sleeping under the stars, a bivy may also make you warmer by adding a shell layer that does not "ripple" as much. If you are out in the wind in a bag with a thin shell it will ripple and lose the warm air inside it. A flapping tent pressing against your bag when its wild and windy out side pumps cold air through your bag. A sort of hard shell around your bag makes it more windtight.

As others have said - the overbag is the trick, however it may be simpler than you think. If I get cold I wrap my down coat over my torso outside of my bag. It gives the bag another couple inches of loft.

I think down baby blankets laid over the top would do just fine. And don't forget the Norweigen saying - green reindeer hides make the best winter nattresses.
Jim S (:->)

9:59 a.m. on March 1, 2003 (EST)
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Sleds

Quote:

Quote:

About the sled - would rope work? I realize there may be some problems with down hills, but the terrain we are going on is pretty mild. It seems like having rigid poles may be hard to ski with?

Yeah, don't let Bill fool ya, when those PVC poles ram up yer behind side, and bust, won't be no fun a'tall

My Mountainsmith sled has two piece metal poles. I have skied down the side of mt Shasta pulling it with a 60 pound load. It actually made the descent easier!!!!!! The extra momentum busted me right through icey crud that might have otherwise made it difficult.

As far as a rope on gentle terrain. The way to do this is to attach a really light cheap kiddies sled to the back of your pack like a turtle shell. When its level and the snow is firm, through down your pack and tow it, but up or down hill or through deep powder, pick it up and carry it.

The real solution is ultralight winter camping, however when oney buddy and I go, we take two sled and over 100 pounds of gear and food. Ofter a small Smokey joe and ten pounds of mesquite charcoal - however be careful or the sparks from the mesquite may burn up your gear. Sleds are coll only when the snow permits easy towing. Like on perfect snow it takes 6-8 pounds of force to pull a fifty pound sled where its level.
Jim S

October 20, 2014
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