Larry writes from Frankfort, Kentucky: "I bought a 30 year old mobile home and plan to install a suspended ceiling. I've been told I can install 3.5 inch batt insulation across the T's above the ceiling panels. Should I use unfaced batts in this type of installation? The ceiling is flat (inside), and I believe there is some minimal insulation above the ceiling and below the roof, but I haven't been able to verify this. I assume that I do NOT want to add another vapor barrier, since there should already be on in the roof/ceiling. Is that correct?"

Answer: Yes, that is correct; you do not want two vapor retarders in any one assembly. The recommendation to use or eliminate the vapor retarder, depends on ventilation. If ventilation above the ceiling is adequate or there is already a vapor retarder in place, unfaced insulation can be used.