Hi mtnman

Mine has only been used for one night (I haven't been out since) just to test it out. It was a very humid and cold night and woke up with a very small damp patch on the outside of the foot area. My Contrail was coated with condensation outside (as was my garden furniture) and some inside so I would say that it breathes well. The rectiflex (?) bottom is as thin as silnylon but softer. I don't use a groundfloor under my Tarptents but I would under the bivy to protect the mat or the bivy if you use the mat inside. (I toss and turn ...)
Franco