On 27 Sep 2003 at 20:00, Marvin & Janet Hamm wrote: > Isn't the point of a vapour barrier to keep your warm body vapour in > the bag, thus reducing heat loss? That's a secondary use. To be comfortable, it works best when the air is quite dry - like cold winter air. > Would that not increase the > humidity of the insulating sleeping bag and thus rule out the use of a > down bag over prolonged successive nights? The vapour barrier goes on the inside of the bag, not the outside. It does the same thing as a vapour barrier in your home - it keeps the insulation dry. This is it's primary use. If you camp in below-freezing conditions without a vapour barrier, the vapour will condense inside the insulation. Pack up your gear and the condensed water will freeze. Several nights of this and you no longer have a sleeping bag, but a popsicle. IIRC, it was a combined Canada-Russia trans-polar ski expedition that showed the effectiveness of this. The Canadians had vapour barriers and the Russians did not. The latter suffered from constantly wet sleeping bags. This was aggravated by the fact that the humidity on the Arctic ice cap in summer hovers around 100% even though the temps are slightly below freezing! Nothing dries out, sores on your skin don't heal etc. Not many of us would have to worry about a vapour barrier for kayaking. They are not so useful in warm weather. Mike *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Sun Sep 28 2003 - 08:40:17 PDT
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