attic woes

Had an inspection today,and in the attic there was a “black, somewhat powdery substance” on the plywood sheathing. The entire attics sheathing was in great shape,1970’s house, however there was this one area above the front porch overhang (about 15’ x 6’) that had this black substance on it. The entire home was insulated with yellow batt insulation, however, the area over the porch had “newer” pink batt insulation that was installed over the porch soffit vents. Now I know that there is no need for the insulation, but is this what caused this black crap on the sheathing? inadequate venting? Mold? The rest of the home was vented fine (ridge & soffit vents (no insulation blockage). Please help if you can, thanx in advance.

Sounds possible, do you have pics?

Any chance that the porch below contained a barbecue grill sending up one of them thar balls o’ fire? Might explain the new insulation, too.

OK. 1970’s house. The black substance sounds a lot like Cladosporium, a common mold, but no way to know from the info. With me, 70’s or 80’s house always means check the bathroom vent hoses, most of them I’ve seen had no outside exhaust, just pointed at the soffet vent, and mold results. Cladosporium and Aspergillius grow really easilly with blocked or non-existent vents; Aspergillius would probably be dark but most likely wouldn’t be black though; Cladosporium is one of the molds with a black coating to protect it from UV light. Maybe take a “lift sample” and send it to ProLab or another lab for identification; or they could tell you it’s soot or something like that?