I am in the process of air-sealing, baffling, and reinsulating my attic. The existing fiberglass batt insulation is from 1985 or so and is about 6-8″ thick. It is wrapped in a vapor barrier on all sides and has been run between the floor joists in the attic currently. I have been moving all of the existing batts and have been piling them in a corner while I air-seal with Great Stuff foam.

My original plan was to buy brand new R30 faced fiberglass batt insulation for between the joists, and then buy brand new R30 unfaced fiberglass batt insulation to run perpendicular to the joists, giving me the R60 level that is recommended for where I live. I was planning to throw out the old insulation, but the more I think about it the more I don’t know what to do with it. On the one hand, it seems like a waste to just throw it away, but on the other hand it doesn’t seem a decent enough quality to use in the place of one of the R30 purchases I was going to make.

Is there any harm in removing the vapor barrier from the old insulation and piling it on top of the two layers of R30, to make a third row? This would give me above R60 levels of insulation, which would probably have hugely diminishing returns. However, if I’m just going to throw the insulation out anyway, then what is the harm in adding it on top for a little extra coverage?