VB liner for sleeping bags

Paul,

Better to use Vapor Barrier Clothing (VBC) rather than a Vapor Barrier (VBL)Liner. Use of VBC or VBL are generally recommended at temperatures below freezing. When using VBC you will not experience the kind of problems of moisture build up that you would experience with a VBL.

VBC will take much of the place of thermals in your sleeping bag. This clothing will maintain the moisture against your skin and it will not soak through the clothing worn outside of the VBC (but inside your sleeping bag). You will need to experiment to find out how much clothing that you require to keep yourself warm when using VBC. The heat generated from your body should be sufficient to dry out wet/moist clothing while you sleep even though you are wearing VBC.

VBC including top, bottoms, socks, and gloves can be gotten from sources including Stephenson’s Warmlite: http://www.warmlite.com.

Richard,

many thanks for the swift reply.

i had just been reading ’bout Stephenson’s at lunch time – downloaded their .pdf catalog.

now that you mention it, i see the advantages of VBC instead of VBL.

take care,
pj

I would agree that Stephenson’s website has the best explanations dealing with vapor barrier theories. I’ve used VB socks with old HiTec Sierra shoes. The order worn was polypro liner, Smartwool sock, then VB sock. Your socks stay completely dry from envionmental water. The only moisture will be from foot sweat. Your shoes will be soaked. The next day on the trail, sooner or later (depending on weather and temerature) your activity will allow body heat to dry out your shoes.

john,

thanks for replying. appreciate the confirmation on the order of wear.

i’ll give it a whirl.

take care,
pj

p.s.
i’m a bit skeptical of some of the Steph. VB dogma. it’s not so much what they say, but what it doesn’t say about when & how to properly employ VBC. there are still some issues buttonin’ up so tight. back in the 60’s rubber exercise/jogging suits were all the rage. heat stroke & MI (myocardial infarction, i.e. heart attack) largely put an end to their popularity

Accept the information and ignore the dogma (kinda like watching Dan Rather). Also thank Stephenson’s pioneering work in this field.

Richard’s earlier reply to you says it all, you need to experiment to find out what combination works for you individually. I normally wear a VB shirt and socks in my sleeping bag with no condensation problems. The VB shirt also seems to give me the rough warmth equivalent of a fleece pullover.

About the neoprene socks. I’ve got em, I’ve tried em, and I’m still not sure where thier niche is. I relegated them to cool weather kayaking, then accidently found out that Smartwool kept me warmer when wet.

thanks to all who provided me with invaluable info.

i hope to be able to return the favor sometime in the future if the occasion arises.

take care,
pj

I’ll start with theory and then move to my personal experiences. Insensible perspiration is the unnoticed sweat that our skin pores are constantly pumping onto the surface of our skin. This is great stuff when you’re a hunter-gatherer in Africa. When you’re trying to stay warm (in or outside of a sleeping bag) it creates two problems. 1) It pumps moisture in the form of water vapor into your insulation. If you are using a material that loses it’s insulating quality in the presence of moisture, such as down, you’ve got a problem. On long, cold trips, such as climbing Mt. McKinley this moisture will turn your 4lb.,-20 degree sleeping bag into a 10lb. sack of icy down clumps. 2) As the insensible liquid on your skin goes through the phase change to water vapor it draws heat from your body to drive this process. This process is known as Evaporative Heat Loss. By placing a waterproof sack or clothing next to our skin 1) moisture builds up next to our skin slowing down the sweating process and thus decreasing our water intake needs and preventing us from flooding our clothing with sweat 2) trapped moisture next to our skin stops the evaporative heat loss from our bodies by preventing the liquid sweat from evaporating 3) now that the sweat is trapped next to our bodies it can no longer get into our insulation(unless you are breathing into your sleeping bag). Both sleeping sacks and clothing (pants and hooded shirt) will perform this task. The advantage of clothing is that you can wear it when you’re not in your bag. VBLs: 1) protect your insulation from sweat moisture 2) decrease your insulation needs by subverting the evaporative heat loss process 3) decrease your water intake requirements (which can mean carrying less water weight in your pack, spending less time looking for and treating water and expending less time and fuel weight melting snow). This means you can carry less weight and bulk in your insulation clothing and sleeping bag, you don’t have to concern yourself with sweat getting into your insulation and you may be able to decrease the water and fuel weight that you carry!

Sounds like a no brainer! So why isn’t everyone wearing VBL clothes? Because most people find the clamminess of the moisture next to the skin to be unpleasant and if you maintain this moist environment next to the skin for a few days, the bacteria growing in there can create some lovely odors. To ameliorate this problem campers wear a light set of synthetic thermals inside their VBL clothing or bag or use velour lined Stephenson VBL clothing to help the skin to feel drier and more pleasant. This is also why VBLs are generally not recommended for use in temperatures above freezing. The bottom line, as noted in a previous post, is for you to play with these products and techniques in various temperatures and exertion levels and see what works for you. If you are successful you will be able to carry significantly less weight and bulk in cold conditions. I sweat heavily. I wore a PVC raincoat and pants UNDER my clothing while winter camping in CA’s Sierra Nevada and was able to wear much less clothing (we lose massive amounts of heat 24/7 through evaporative heat loss when we are not wearing VBLs) BUT…I ended up smelling like a cheese factory after a couple of days-Yecch! But that’s just me. I hope that you have better luck.

One post made mention of drying clothes inside of a sleeping bag. If this is a down bag I highly recommend against it. The moisture from your clothes will go straight into the down and collapse the loft of the down clumps; and down bags are very slow to dry. If you can dry your clothes inside your down bag and you can sleep warm, then you are packing too heavy a bag and drying your clothes inefficiently. Try a clothes line inside your tent or putting them on wet in the morning, doing some jumping jacks and getting on the trail. Synthetics will dry under Gore-Tex while hiking in the rain. It’s not as unpleasant as it sounds and it beats the heck out of a cold sleepless night in a damp sleeping bag. My experience is that once a down bag gets wet, you’re hiking out and the trip is over.

BAG LINERS are heavy and unnecessary. My Western Mountaineering Ultralite bag uses their gossamer parachute nylon on the inside. I use it a lot; I treat it well; I wash it when it gets dirty and it’s held up fine. Similarly if your tent has a floor, don’t carry a ground cloth; that’s what the bottom of the tent is for. If you carry 2 items that each perform the same task, you’re going to have a heavy pack.

VBL SOCKS I can help you more in this area. Yes, you can use VBL ie. non- breathable socks with all the benefits and disadvantages mentioned above. However, due to the tremendous force, abrasion and blister potential that backpacking feet face, I find it important to keep the feet drier than a VBL allows. The solution that I’ve been using for 15 years is Gore-Tex socks. A pair weighs 2.5-3oz. depending on size. They pack small. If you put on a thin pair of cotton (the death fabric) socks and slide GTX socks and then trail runners or hiking boots on over them and stand in an icy creek, you will be amazed at how warm and dry your feet are. The same goes for heavy exercise in them – even in warm weather. I’ve climbed snowy couloirs with them inside hiking boots with no gaitor. During the last half of my 12 day unsupported John Muir Trail hike I ran 25 miles per day. One rainy, hailing day I wore GTX socks the whole day with no modifications, no foot problems or sock wear problems (and my feet are prone to blistering). The boots may get wet or packed with snow, but your socks and feet stay warm and dry. I have had such tremendous success with these tools that I take them on many day and virtually all multi-day trips. I stepped on a cactus while running in the snow and punctured my first pair that I had been hiking in for 10 years. The replacement model has a much smaller stretch section and forced me to move up 3 sizes just to get them on over socks. This creates loose folds of fabric which I didn’t have with the old model. Fortunately, the folds do not create a problem as proven by my wet day on the JMT. Compared to the ubiquitous GTX boots, GTX socks protect much higher up the leg, do not fail catastrophically when the water level (as in a creek crossing) goes above the garment and can be easily removed in warm, dry weather to allow the feet to breathe even better. <rei.com> Rocky GTX socks (move up 2-3 sizes). $50

NEOPRENE SOCKS – I have used these for 20 years. I use them mostly for snow camping. They provide insulation and work as a VBL although they will leak a little sweat through the sewn seams unless you seal them with neoprene glue (available from S.C.U.B.A. retailers). I wear them against my bare skin with insulating socks over them; and if I’m wearing standard hiking boots in the snow without gaitors, I layer GTX socks over the other socks. If I’ve been wearing any type of non-breathable (VBL) sock during the day I remove them at night to allow my feet to dry out. Neoprene socks are also nice for cold water swimming, creek crossings, rafting and kayaking which often don’t require the superior insulation of thicker, warmer, heavier neoprene diving booties. <rei.com> 4.3oz. Gator and Seirus brands

I hope that some of this information and opinion is useful to you.
Cheers, Al

very informative.

have “bookmarked” the REI GTX socks.
will give them whirl.

many thanks,
pj

I am planning a desert ultramarathon this spring and I'm trying to keep my gear weight as low as possible. I am considering 3 possible sleep systems:
1) Rab Top bag with extra clothing
2) Rab top bag with AMK thermolite bivy sack inside
3) AMK Thermolite 2.0 bivy sack with extra clothes

I have never used a VB and I have no idea whether this is a realistic idea in the conditions that I am going to be in.

Here are the probable conditions:
15 lbs total pack weight, running 20- 50 miles/day with night time temps of 0-5C. Typical humidity is less than 15%.

Is a VB set up appropriate in these conditions?

Uglyboy,
What is your complete sleep system? It is hard to advise not knowing what clothing you plan to use. Also, do the conditions include spring showers? Some deserts get them. "Dry" deserts usually have heavy nightly dew. Will you need some kind of rain shelter? If so, what?

That said, the Rab top bag should take you to 0C without a liner or bivy. And a little extra weight in the bag/sleep system is more efficient than any "extra clothing" you can wear.

You might give some thought to an insulated pad such as a Gossamer Gear Thinlight pad used for insulation rather than padding. At about 2 ounces, the 1/8" pad ought to do the trick.

Since this is a gonzo race, and comfort is secondary, you might consider two (2) of the AMK sacks – one on the outside as unltralight bivy/precipitation protection and one on the inside to keep water vapor from condensing on the inside of the bivy and soaking your insulation. Remember, you will put out a quart of condensate during the night. In other words, sandwich your insulation between two layers of Mylar. I would strongly discourage using a waterproof bivy – of any material – without also using a vapor barrier on the inside.

The outer sack will substitute for a ground sheet, although it will shred eventually. For the duration of the race, that probably won't matter much.

The Rab top bag weighs about 15 ounces, the GG pad weighs 2 and each AMK sack weighs 2. That will give you a 22 ounce (weights rounded up) sleep system that will keep off the dew and any vagrant shower, keep your insulation dry and take you to freezing with no problem.

Unless you carry a lot of water and food, staying under 15 pounds should be easy.

Vick, thanks for your response. Here's a bit more info:

Self supported (carry everything) for a week, except water and a tarp tent.
Sleep in a tarp tent, with a thin berber carpet on potentially stony ground.

No significant risk of rain that I am aware of…

I've been looking at the thinnest GG pad. I will probably need tylenol+immovaine to sleep with that one.

WRT other clothing it will be pretty light – capilene long underwear or possibbly montbell puffy pants and vest.

Is condensation a significant problem inside VBs when you're above freezing all night?

Whatever you do, give it a trial run first.

The one time I used a vbl above freezing was on a 3 day trip where the temps hovered around 5C.

I only wore thin long underwear, and I was soaked. Warm, but soaked. It was better than cold and dry, but not by much.