we have a summer shack that isn't heated in the winter and are trying to decide what kind of ceiling to go with. we were just at menard's and bought 6 boxes of armstrong tiles, then got scared when we read the warning about installing in areas of 60-80 degrees only with humidity less than 70%. there is plywood on the ceiling at present. any thoughts out there? it is just a shack so we are trying to go cheap. thanks a lot.