Vapor barriers largely eliminate heat loss from evaporation, not least by protecting insulation from becoming wet with perspiration.
By way of background, heat is lost through 1) evaporation 2) convection and 3) conduction. The relative significance of each is highly variable, depending on conditions.
VP socks are excellent. Either sturdy plastic bags, or coated nylon, over a thin sock, topped by a thick sock, then boot. The thin sock gets wet but the foot stays warm -- even in moderately extreme cold!
As a lining for sleeping bag they DO add a lot of warmth. Very effective, though delicate, VP sleeping bag liners can be made with kitchen trash bags, duct tape and scissors.
The degree of added warmth in sleeping bag seems (subjectively, to me) to increase as temperature drops. But one cannot wear a full complement of clothing inside the barrier, or the clothing might become too damp.
Warmth from added clothing may outweigh warmth added by barrier, thus the fuss seems worthless for relatively brief trips.
On winter trips of longer than a few nights, they could be quite useful, given difficulty of drying out built-up of condensation in sleeping bags, which, after a single night (my winter typical trip), is often considerable in cold weather without a VB.
By way of background, heat is lost through 1) evaporation 2) convection and 3) conduction. The relative significance of each is highly variable, depending on conditions.
VP socks are excellent. Either sturdy plastic bags, or coated nylon, over a thin sock, topped by a thick sock, then boot. The thin sock gets wet but the foot stays warm -- even in moderately extreme cold!
As a lining for sleeping bag they DO add a lot of warmth. Very effective, though delicate, VP sleeping bag liners can be made with kitchen trash bags, duct tape and scissors.
The degree of added warmth in sleeping bag seems (subjectively, to me) to increase as temperature drops. But one cannot wear a full complement of clothing inside the barrier, or the clothing might become too damp.
Warmth from added clothing may outweigh warmth added by barrier, thus the fuss seems worthless for relatively brief trips.
On winter trips of longer than a few nights, they could be quite useful, given difficulty of drying out built-up of condensation in sleeping bags, which, after a single night (my winter typical trip), is often considerable in cold weather without a VB.
Vapor barriers
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