Richard writes from Wilton, Connecticut: "My home is located in the north east. It has a cantilevered segment that extends approx. 32 inches beyond the foundation. This portion of the house is 14 feet wide and provides part of the space housing a laundry, bathroom and an exterior door.

"I recently removed the plywood that covered the underside of this bump out and discovered that the builder had installed fiberglass insulation with the paper vapor barrier facing down, away from the heated or living space.

"Water lines, waste lines and electrical cables do pass through the house band to this cantilevered structure from a section of the basement that houses the heating system at that location.

"I plan to use a can of expanding foam insulation to create an air seal around all of the openings that allow the passage of heated air from the boiler room out to the underside of the cantilevered structure. I would appreciate some advice as to the insulating material and installation method best suited to this structural configuration."

Answer: Fiberglass is appropriate type of insulation to be used here. However, the paper vapor retarder should be installed toward the warm-in-winter side.