Woody,
My first thought after reading about your Bivy experience was ... that happened to me also experimenting with Bivys.
This happens with Bivys because ... the non-breathing waterproof fabric is to the outside with coldest air temp creating condesation toward the heat source.
I'm not sure there is solution with Bivys because to minimize condensation using vapor barriors, one needs to keep the non-breathing fabric (VB) closest to the highest heat source (you, at 98*) while keeping one's insulation nearest the outside cold temps.
So, having the vapor next to you or your 2nd layer, will maximize vapor barrier technology thus
keeping your gear the warmest with the lightest weight which is
www.dplightweightbackpackinggear.com total focus.
We aren't sure how much heat retaining temperature one gains using vapor barriers, but for the average person, we are thinking at least 15*.
Happy trailzzzzzzzzzzzz
dp Dave
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