been to look at a job today ... a barn convertion.. everything is studded out and the walls are all battoned .. the site manager says he wants 55mm insulation on the exterior walls and 12.5 mm board .. but then he mentioned a couple of things i wasnt sure about .. the window reveals need insulated backboard . and the ceillings and walls upstairs are to be wallboard 10 .. im not too sure what hes refering too .. also whats the best form of sound proofing between the boards ? i really need some help ....