We live in an old long leaf pine farmhouse that has no insulation in it. We are going to be putting a new metal roof on the house. The attic of the house was made into living space and so there is really no attic space between the upstairs ceiling and the roof itself; just the depth of the 2x4 roof rafters. We are concerned with several aspects of this project. Want the best insulation material that will help to cool down the house as we live in Texas. The roof currently has shingles on decking. They are going to remove the shingles and put on 30# felt paper and we want to know can we put insulation on top of the decking and install the metal roof directly over the insulation into the roof decking? The roofers are stating that you need 1 x 4 lattice and then putting the insulation between the lattice. Another concern is about the insulation possibly getting moisture on it?? Is a radiant barrier something else that needs to be added or does some insulation come with a radiant barrier reflective sheet as part of the insulation? Just looking for a good unbiased opinion from someone else. Thank you so much for your reply.
You can install insulating foam panels directly to the existing roof membrane (decking). The panels are backed with OSB wood panels (the OSB would face out/up). So basically it would be roof decking, then foam insulation, than bonded OSB wood decking. Over it all you would place roofing felt and roofing material. Check out this short video.