I agree with jb and disagree with Harold on this one also. I wasn't sure I wanted to argue the point with Harold since his "hydronic network" name implies he is an expert in the area of hydronics. I don't claim to be an expert so if Harold has some additional info to back up his post, then I would be interested in hearing it. Otherwise conventional wisdom for most of the country says you want a solid plastic/kraft paper vapor barrier on the interior of walls. However in Florida, they recommend the vapor barrier on the outside of walls above ground level because of their heat and humidity and lack of cold weather.