KidKruger Wrote: ------------------------------------------------------- > RD this is the bit that I didn't get, either. > A non-porous barrier being used as a breathable > layer ! Don't worry, by the time he nailed all the floor boards back down it would've resembled a sieve! > Clearly his underfllor is well-ventilated (as is > mine), so you'd need to assume the room above the > floor is also well ventilated. As long as > underneath is ventilated my thinking is he won't > actually get condensation underneath (even if he's > not used an appropriate barrier material). Exactly. Also worth noting that a company like Dupont aren't advertising it as being used in such a situation, potentially it could be a massive market for them, but they don't, which suggests it's just not needed...