Doreen writes from Randolph, Massachusetts: “We just bought owens corning at home depot and notice there are wet spots of black oil on the paper side. What is this and should it be there?
The black coloring sometimes seen on the Kraft facing of our building insulation is asphalt adhesive. The adhesive attaches the paper to the fiberglass and gives the paper its vapor retarder qualities. On occasion this asphalt can bleed through the paper. It is a rare occurrence, but does happen. This does not adversely affect the performance of the insulation.
