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Bill, and anyone else who knows about this stuff, we are having a discussion on TLB about vbl clothes. I have read about vbl for years, but never tried it since I really haven't been out in ultra cold weather which is what it seems to be made for.
Jack Stephenson was a big proponent of vbl and his company sells vbl clothes that basically look like people shaped industrial strength plastic bags. I'm sure other companies make similar stuff.
I read Stephenson's explanation of how it works on their website, but it seems to me that if you are skiing or snowshoeing and generating a lot of heat, then you would want to be wearing something breatheable so the heat and sweat could escape.
Once you stop moving, then the heat production slows down after a few minutes and therefore, you put on a jacket of some sort and maybe a hat to insulate you and retain the lower level of heat you are generating.
But, if you are wearing a vbl shirt or pants, for example, while skiing, doesn't all of the heat and sweat you generate stay inside the jacket or pants and you get hot and wet? Isn't the point of breatheable fabrics like eVent or Gore-tex to prevent that from happening?
I can see the vbl theory working at night, because you don't want your body moisture you are "outgassing" for lack of a better term to wet your bag from the inside,but it just doesn't make sense to me if you are moving and generating heat and sweat.
I have spent a lot of time underwater in a wetsuit, so I know how that works. Stand around in one in the hot sun for a few minutes and your temperature climbs quickly. To me, a vbl works about the same way, except in a wesuit, you are actually heating up a thin layer of water that keep you warm because it is insulated from the water surrounding you.
The eVent/Gore-tex theory vs. vbl theory can't both be right, can they?
Bill, were you using vbl stuff in Antarctica or on any of your other trips, like Denali?
What am I missing here?