looking at purchasing a 23 yr old cedar log home with truss roof repaired 3 years ago w/metal roofing. Its been vacant/unheated for a while and the cedar cathedral ceiling has spots of black mildew/mold all over it. I dont see this on walls. What could be cause of this and how can it be eliminateed? The entire interior is wood, I worry about changing the patina on one part and onot all. What else should I be concerned about?