Russ writes from Pittsburgh, Pennsylvania: "How do recommend insulating an 18th century frame house in Virginia? The interior surfaces are lath and plaster and will remain in place. The exterior is clap boards over the frames, no sheathing, no wrap. The clap boards will be removed as part of restoration so the outside walls will be open to accept insulation. Do I need to add the sheathing and house wrap?"

Answer: Foamular® extruded polystyrene insulation can be added to the exterior to increase the R-value of the wall assembly. Owens Corning also markets PINKWRAP® housewrap, an optional air barrier. We recommend Kraft-faced Fiberglas™ insulation for inside the wall cavity with the vapor retarder installed toward the warm-in-winter side of the wall.