In cold - does wrapping in plastic bags help?

“My father and I disagreed on the matter.

He said you'd be worse off - sweat.

I said you'd be better off - trap heat.

Who's right?”

“Obviously not around your face, though.”

“In the past a waterproof liner was considered a vapor barrier that helped enhance your clothing's insulating ability by about 10 degrees of insulating ability. The best example are the vapor barrier booties in mountaineering boots and vapor barrier liners sold for sleeping bags.

IT would probably also be a good idea to be wrapped in plastic if you were freezing to death. Helps your flesh resist "freezer burn" so you'll be a good lookin corpse when the coroner comes to pick you up and your relatives have to ID your body!”

“Princeton Outdoor Action Guide
4. Vapor Barrier Systems - another way to stay warm in the winter is through vapor barriers. The body is always losing water through the skin even when we are not active. This loss is known as insensible perspiration and occurs unless the air humidity is 70%. This insensible perspiration goes on at the rate of nearly half a quart every 24 hours. Since it takes 580 calories per gram to turn liquid water into water vapor, heat is continually lost through insensible perspiration as well as through sweat from any activity. A vapor barrier is a clothing item which is impervious to water thereby serving as a barrier to the transportation of water vapor. When worn near the skin it keeps water vapor near the skin. Eventually the humidity level rises to the point where the body senses a high humidity level and shuts off insensible perspiration. This prevents evaporative heat loss and slows dehydration.

Vapor barriers should not be used directly against the skin because any evaporation of moisture directly at the skin surface leads to heat loss. Wearing polypropylene or some other hydrophobic layer between the skin and the vapor barrier allows the moisture to be transported away from direct skin contact. There is no doubt that vapor barrier systems are effective for some people in some conditions. The issues you must consider before using a vapor barrier are activity level, amount you naturally sweat, and "moisture comfort." If you are not active, such as when using a vapor barrier liner at night in a sleeping bag, the system will work well. A vapor barrier sleeping bag liner will typically permit you to sleep comfortably in temperatures 10 - 15 degrees colder than in the bag alone. However, some people find that they are not comfortable with the level of moisture in the bag and fell clammy. If this interferes with sleeping it may be a problem, better to have a better insulated sleeping bag. Vapor barrier liners for sleeping bags also help in another way. In cold conditions, the moisture from your body escapes upward through the bag, when reaching the cold outside of the bag it condenses into liquid or event frost. Over a number of days this moisture level in your bag increases. If you can't dry out the bag it will slowly get heavier and heavier as it holds more water. With a down bag, this moisture can actually soak the feathers and cause the bag to loose significant amounts of loft (dead air space), thereby reducing it's effectiveness.

When you are active, like snowshoeing, and you are wearing a vapor barrier such as a vapor barrier sock, you must carefully monitor how you sweat. If you are someone who sweats a lot with activity, your foot and polypropylene liner sock may be totally soaked before the body shuts down sweating. Having this liquid water next to the skin is going to lead to increased heat loss. If you don't sweat much, your body may shut down perspiration at the foot before it gets actually wet. This is when the vapor barrier system is working. The important point is that heat loss comes from water changing state from a liquid to a gas. Liquid water next to the skin leads to significant heat loss. Water vapor next to the skin does not. You must experiment to determine if vapor barrier systems will work for you. "”

“How cold are you talking about? Depends on the activity. If you are just wrapping your feet for short periods of time. While crossing water or deep snow, good idea, if that is all you have or can afford. And maybe for hand protection for short periods of time also. But for long term wearing, bad idea. You would end up frozen stiff ? Isn't that what happens to moisture, plastic is a great windbreak, but not much of a insulator.”

“Plastic is a bad idea. Due to the fact that the body is constantly trying to keep the skin moist (around 70% humidity) plastic has a tendency to trap the moisture and give no insulating properties. Sure it will keep the moisture off of your skin from the outside, but it's the moisture on the inside that will do you in. The moisture levels will build and if you use it on your feet you are risking trench foot. In one day of hiking you could damage your feet to the point of loss of mobility, especially if you are a heavy sweater. You would be much better off to buy a pack of cotton socks and change them constantly rather than put plastic in your boots. Sweat in the cold climates is a major enemy. You don't want to stop it, but you do want to manage it. With the new technologies available today it isn't hard to manage. Polypro or silk liners and looped wool socks make good boots great. Some people can't wear liners so just go with the socks. Smartwool is a good choice. UnderArmour Cold Gear is another good choice for an underlayer, it wicks the moisture away from your skin while keeping you warm and dry. I could go on and on about winter camping and survival... I taught a winter survival course at UW Stevens Point for 6 years and have been winter camping in Northern WI since I was a kid. BAck then it was layer upon layer of crappy cotton, now I can afford the good stuff.”

“I think keeping things hot or cold matters if you keep it in an insulated bag which hold in whatever you have in their either hot or cold.”

“If I'm biking and it's raining and cold or windy, I put plastic bags over my socks inside my shoes, and plastic gloves under my biking gloves. Makes a world of difference.
never while hiking.”

“Princeton's good, but I'm a CANUCK!

First, VBL's are good only if the temperature is well below freezing, say -15°C or 0°F.

Contrary to what Princeton says (what can they know about cold in New Jersey for chrissakes?), a VBL should be worn over the wicking liner socks or over you poly underwear in a sleeping bag.

In these conditions a VBL can even be considered essential to comfort, although to be fair I've never needed a VBL in my plastic boots whch tend to be overkill round here (southern Quebec - northern NYS).”

“Who was right?”

“I hate VBL even at 40 below. I don't like the clammy feel.

(White Mountains and Chena River areas, AK)”

“Gremlin speaks with true wisdom.

I think some people misunderstood the concept of the VBL.

Its proper use is really ONLY inside a sleeping bag, OVER the polypro underwear.

It keeps moisture from wicking into the sleeping bag and ruining the insulating properties as well as helps your body maintain a good level of humidity.

But, like Pathman says, some people hate it because it can make you feel a bit clammy.”