Dude, despite your claims that you do your research, you must not read all the posts above. Tyvek/Polypropolene bivy from Miles Gear
And my experiences with a MLD superlight is condensation nearly 50% of the time
a quote from my own piece:
"I have scoured the internet and there is no miracle fabric, all bivies have condensation/frost from time to time but the ones with the least mentions of condensation are made of all eVENT like the Integral Designs All eVENT bag cover (now discontinued) and the OR Advanced Bivy, both with vapor and air permeable top fabrics. [8, 9, 10]
The ones with a breathable nylon top with a good DWR and minimal silnylon floors, but without high bathtub floors, are the next best. From reports there seems to be something about the waterproof bathtub floors that leads to more condensation. This is apparently why the ones made of all eVent (top and bottom) have fewer reports of problems with condensation.
The worst offenders are any of the polyurethane membrane/WPB materials that are only vapor permeable like full Gore-Tex, Montbell DryTec, Mountain Hardware Conduit, etc. I have used or been around many of these and they all have had bad condensation problems.
One of the things that seems to happen with the vapor and air permeable fabrics (eVent, Gore-Tex FLO2, Gore-Tex Respiration Positive, Exchangelite and the less waterproof Gore-Tex Dryloft now Windstopper ) is that the membranes are laminated onto fabrics, and many lined with Tricot, that seem to help wick or pass the moisture through the material. I feel that this is why my old OR bivy had so few condensation problems, it has an almost cottony feel to it. The problem with these fabrics is they are heavier and the lightest of these bivies on the market are 13 oz. and up, with most around 18 oz. and they are crazy expensive ($200 plus)."