saf1901 Â Â 10 #1 Posted April 20, 2011 In the process of converting our cellar, and looking for insulation to go on the floor above the initial concrete pad and underneath the underfloor heating/screed layer, The issue is head room and the thinner the better as long as it meets the required U value- so does anyone know the thinnest insuation with the highest U value? Â Thanks in advance Share this post Link to post Share on other sites Share this content via...