Hi guys, I have removed all the plaster from 2 ground floor rooms ready for the outside walls to be insulated ,ie 25mm battens,celotex T break 50mm board,then 12.5 mm plaster board over,my question is, do I put any thing in the gap between the wall and the celotex,the plasterer says he puts 30mm of fibre glass in this space to remove any air gap,(under instruction from his gaffer),and the damp man said to leave it as an air gap,the damp man also suggested foil backed boards for the internal walls,as a belt and braces approach, thanks for your indulgance