Well if your where its cold and you mylar you must have greauu t insulation, or the wall will get wet and moldie. It will not take long and your walls will sweat and the plaster will fall off the walls. Now with flat white with a mildew preventer in the paint you will solve 2 problems , the wall falling off and mold. I have used both and the best way is to make panels of pvc pipe and tape the mylar to it. Spraying the walls with 3m spray will work , but if you ever need to take it off you will need to put up new wall board , tape and joint compound and sand primer and paint walls ,,,,,,,,DO NOT USE 3m it will cost you a bunch in the long run.Flat white is well worth it because you paint every thing