Sean writes from East Hartford, Connecticut: "My attic has 3.5 inches of fiberglass between the joist and additional 12 inches of blown-in fiberglass. Can foam board be laid down on the 2 foot wide plywood catwalk? Can it be layered to provide a higher R value? Finally, can a layer of plywood be placed over the foam board to maintain the use of the catwalk?"

Answer: The use of FOAMULAR® extruded foam insulation is not recommended in this application. The FOAMULAR insulation may slow the transfer of moisture through the existing layers of fiberglass insulation. Also, your local building code probably requires that foam insulation be covered with a 15 minute thermal barrier, such as a flooring material, for fire safety.