Rick writes from Ocean City, Maryland: "I'm finishing off a portion of my attic space. It is a large room with walk-up stairs. I only plan on finishing one half of the attic and the walk-up stairs. There will be a finished wall facing the stairs. Beyond that wall will be an unfinished storage area that will be accessible by an insulated door. I am thinking about how to best insulate that wall. I intend to place fiberglass insulation with the vapor barrier facing the living area side. I would like to place 'sheathing' or rigid foam insulation product on the unfinished room side of that wall to prevent heat transmission through the wood framing. I now see that the FOAMULAR insulation must be covered with drywall. Does this mean I have to finish both sides??? I have a knee wall also. The research that I have seen suggests adding FOAMULAR to the outside side of a knee wall for additional insulation. It doesn't say anything about covering that with an additional layer of sheathing. What should I do?"

In most code jurisdictions FOAMULAR can be left exposed on the attic side provided you have drywall on the interior side. A friend of mine put PINK FOAMULAR on the knee walls when he built his home and the local building inspector had no issues with that.