Up on the high ceiling there is: 1) New dry wall 2) Styrofoam 2" 3) Old gypsum board somewhat moldy, not sure to what extent 4) some tin foil 1950's? 4) Moor vents (new) 5) roof with airflow to outside vents. I was thinking of covering it all with poly 6mm, then finish it. Main reason is to keep the mold out and save me from tearing it out and rebuilding. Good idea, or could it make it worse?