I have thought about using cuben fiber as the liner in the construction of 3 UQ's I am making. I got this idea from Grizz's DIY underquilt ( http://www.hammockforums.net/forum/s...ead.php?t=6466 ). He uses sil nylon as a vapor barrier. I think sil nylon and cuben fiber would have the same effect. Now correct me if wrong if the liner is not breathable what would be the positive and negative effects. I plan to conduct more research on heat conduction but I for now have some common sense questions. If the liner is not breathable vapor and moisture from my body will not penetrate the material. Thus conducting thermal energy to the down. The cooler more dense moisture will obviously condense under myself or in my clothing. Well I reckon I could turn on my side when I am getting a little sweaty. Heat spontaneously flows from areas of higher temperature to areas of lower temperature coming to an equilibrium. Heat conduction moves through mass or matter where in convection transfers in bulk motion of matter. The thought I have is what happens when cool air and hot air interact and form moisture in between the shell and liner. Well Heat rises and cool air falls. The cool moist air would be advected by the cool air's current of movement flow through the breathable shell. The warm hot air rises and would conduct heat energy through the liner. hELP ME OUT ON THIS EVERYONE.