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Dav Harzin

Cold Weather ? "What the heck is a vapor barrier or VB"

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Posted (edited)

I personaly use this idea, works very good in dry low humidity, but with caution does not work well in 'wet/cold' weather.

 

 

 

 

It was mid October when we left for our last hike of the year. The

temperature high on that first day was 65ºF, so we knew we were in for

a chilly night. As we started settling into camp that first evening,

the sun dropped behind the mountain range and it felt like the

temperature instantly dropped 10 degrees - funny how that happens up

high in the mountains (we were at ~10,500 feet). My buddy started

scurrying about pulling out all his cold weather gear; goose down

parka, polartec vest, heavy wool shirt, thermax long sleeved T-shirt,

thermax long-johns, polartec sweat pants, wool cap, and wool gloves.

There he stood, all decked out to do battle with the cold, looking as

wide as he was tall. Poor fellow could barely move about to do any of

his camp chores, and surely without the slightest bit of grace or

dignity. I, on the other hand, put on my vapor barrier (VB), a long

sleeved thermax T-shirt, a heavy wool shirt, thermax long-johns,

polartec sweat pants, a wool caps, and fingerless wool gloves. My

buddy looks at me and says "putting plastic against my skin is a sure

way for me to be miserable." This is the unfortunate presumption made
by most individuals on the use of a VB.

 


"What the heck is a vapor barrier or VB" you ask. It's a barrier

between your skin and the elements, and plastic works best. I use a

tall kitchen trash bag and cut holes out for my head and arms. The two

basic principles behind the use of a VB are as follows:

 


1. The colder it is, the better a VB works (I personally would not

even consider using my VB unless I were exposed to temperatures below

50ºF for any considerable length of time). The warmer it gets, the
more a VB loses its comfort value.

 

 

2. The closer to your skin (preferably on it, but T-shirt, VB, T-shirt

will give 90% of the results) the more effectively a VB will perform.

A VB worn away from the skin can cause gallons of water vapor. Example

- a waterproof parka/anorak is essentially a VB worn away from the

skin, and I am sure you are aware of how sweaty you can get in rain

gear; this event alone is what prompts most individuals to be
skeptical about VBs.

 

Body heat makes the difference! Since the VB is warmed by the body,

the body's comfort layer (more on this to follow) is easily maintained

directly on the skin with minimal vapor output. If the VB is not kept

warm, as with rain gear, the temperature differential will invite you to sweat.

 

 

HERE ARE SOME INSIGHTS ON THE MYSTERIES OF A VB - based on research (Robert Wood) and practical experience:


The skin, as a highly sensitive organ, likes the air temperature on it

to be about 75ºF, ranging from 72ºF in the hands and feet area to

approximately 78ºF in the head and upper torso area. So what the body

(your skin) wants is a quarter inch layer of moist air protecting it

at all times. Moist does not mean wet - moist, comfortable skin feels

dry to us, truly dry skin will quickly chap, crack, and soon bleed.

Disrupt the protective (comfort) layer and the body goes wild trying to restore it.

 


If you heat up the comfort layer, the sweat glands open up and start

pumping out water vapor to cool the body back to that optimal comfort

zone. If you cool down the comfort layer, the sweat glands shut down

and the body starts to shiver, again, trying to regain that optimal

comfort zone. A VB works because it utilizes, rather than ignore, the

body's continual water vapor and heat production activity.

 


Here is a practical example of disrupting the skins comfort layer - on

a 68ºF day you can comfortably walk to the store in a long sleeved

shirt, but try jumping into a 68ºF swimming pool - it'll feel like ice

water. On the 68ºF day your body can easily maintain a 75ºF comfort

layer, but in the water it cannot; the sudden 7ºF drop on the bare skin is a shock.

 

As outrageous as a VB sounds, informed consideration of our bodies

behavior shows it to be perfectly logical. World War II ski troops

afflicted with trench foot and frostbite from continuously wet, cold

feet had their dilemma miraculously solved by the use of VB socks,

which also solved the frozen foot problem during the Korean war. A

properly used VB will increase body warmth by 20ºF.

 


The concept of a VB contradicts all our good sense about staying dry

and comfortable, and the system takes some tinkering and getting use

to in the field. As the temperature gets milder, the system's

efficiency makes overheating rather easy. The basic field use concept

is that a VB requires ventilation, if not removal, in weather that's

warming up, or when physical exertion raises the skin temperature near

the sweat level. So, don't JOG to the top of Whitney with a VB on!?!

 

 

The preceding is a simple brush on the details of the effectiveness,

use, and benefits of a VB, and is not intended to challenge anyone's

opinion. I merely wanted to present the perspective of a devout user

and believer of VBs. One of my staple survival/cold weather kits is a

tall kitchen trash bag for my torso (essentially a plastic vest) and

two produce bags (the ones from the market) - one for each foot, and

they have kept me comfortably warm through some rather adverse

conditions (Mt. Whitney in late April).

 


If you are skeptical, consider conducting this simple test on your

next outing in order to demonstrate the virtues of a VB. On a COLD

morning, or evening for that matter, put the following on ONE foot - a

produce bag (directly on the skin), a sock, and your boot. On the

OTHER foot put on a sock and your boot (if you wear camp socks and

shoes, use them instead, the effects will be more dramatic). Then go

about your morning/evening camp routine and you will be amazed at the

comfort difference in each foot.

 


So now you ask, "why aren't outdoor magazines raving about VB's?"


Economics, my friend! Do you think that outdoor clothing manufacturers

would continue to spend tens of thousands of advertising dollars in a

magazine that runs articles touting the virtues of a 5 cent

alternative to the $200.00 - $300.00 whiz-bang parkas being advertised!

 


Well, I have rambled on long enough. As you have gathered, I am a true

believer in the use of VBs, but I also recognize that one man's

treasure can be another man's rubbish. Happy Trails!

 

About the Author
Lu Seli (lseli@gnp.com) lives in the Los Angeles area with my wonderful wife and our three terrific kids. I am a Quality System consultant for the manufacturing in

 

Edited by Dav Harzin

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Posted (edited)

Vapor Barriers work, not doubt about it... but be careful: barriers don't "breathe".  For example, if you put on a garment, then a plastic bag, then your outer garment, moisture (sweat) will accumulate inside the barrier.  That can lead to hypothermia, as everything UNDER the barrier will be soaked.  When you are not active (generating heat) your body temperature will cool down even more rapidly due to the excess moisture/evaporation.  

Edited by John Last

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11 hours ago, John Last said:

Vapor Barriers work, not doubt about it... but be careful: barriers don't "breathe".  For example, if you put on a garment, then a plastic bag, then your outer garment, moisture (sweat) will accumulate inside the barrier.  That can lead to hypothermia, as everything UNDER the barrier will be soaked.  When you are not active (generating heat) your body temperature will cool down even more rapidly due to the excess moisture/evaporation.  

Agreed on 'under' Dont ever do that.  Mostly use this idea when aroud camp and NOT working excessively, then it works good.

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