Hi, I've got a backyard studio 24'by24',I'm going to put the celling in. I have some 4'by8' lightweight sheets of some kind of foam board that the contractor left, he said it was for sound insulation. Would this be better than 1/2" sheetrock for a celling? I was considering using this for the ceiling and using ply wood for the flooring material in the attic. If the foam board is ok to use should I use fiberglass insullation between the attic floorin and the ceiling or would it be better to leave an air pocket? For the walls I'm using R-19 fiberglass insullation and plan to use 5/8 sheetrock with a flexible chanel between the studs and sheetrock. Thanks, Don