Lisa writes from Phoenixville, Pennsylvania: "I have an 1888 3-story Victorian in a cold-climate region. The 3rd story is an A-shape room with a steep pitch a flat ceiling. It is also a heated living area (radiators). There'\'s a closed knee wall area with a little door that I can access and then at the top of the room there's access door that leads up to the tip of the house. In this area it looks like someone blew in a grayish loose material which comes up to the top of the rafters.

My question: Is it possible to lay down insulation perpendicular to the rafters on top of the existing insulation? And if the loose contains no vapor barrier, should i have a vapor barrier and can I place it on top of the loose insulation or would that cause moisture?"

Answer: We recommend adding unfaced insulation (no vapor retarder) in perpendicular alignment you mention. The use of a vapor retarder over existing insulation could lead to moisture problems.