Originally Posted by d-p
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
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*.
d-p, thanks for the primer on VB technology. I'm trying to assess how this applies to my intended use, which is to insert it between the layers of my hammock for under insulation in conjunction pads. If it's best to have the VB closest to me, then I assume I should place the pads under the VB. My pad system is a partially inflated Thermarest Pro or Exped Downmat 9 for colder temps, with half a Z-Lite accordion ccf pad crossways under my upper torso for shoulder insulation.
Is my assumption correct about where to place the VB, and would it really add much? I don't need it for top insulation, so I don't plan to crawl inside it with my down sleeping bag on top.