Mark writes from West Springfield, Massachusetts: "I read your blogs regarding insulating over existing. I want to do this as well. The current floor insulation in my attic is quite strange. There is paper on both sides and the insulation is in the middle. Can I put unfaced insulation on top of this or should I remove and put in R-25, faced down toward living space below. I would like to just add unfaced R 19, but not sure with this old (but dry) 2" insulation."

Answer: I would leave the old insulation in place and let it continue to work for you. Since the existing insulation seems to already have a vapor retarder, add unfaced insulation. Regarding the fact that the existing insulation has paper on both sides, you generally don’t want a second vapor retarder but there can be an exception when the insulation you are adding is twice the R-value or more than the insulation already in place. That is clearly the case here. Another option is to freely slash the top paper on the existing insulation. If you want to achieve even better energy efficiency, I recommend placing another layer of unfaced batts perpendicular to the R-25 afterwards. For maximum efficiency you will want to try and achieve up to R-60.