David writes from Poughkeepsie, New York: "I have an older home with 2x4 exterior walls which had never been insulated. The studs are 22.25in apart. I plan on custom ordering fiberglass insulation to the correct width and depth, but I am concerned about the low r-value (r13). How can I boost this value up given the small amount of depth I have to work with?"

Answer: You can boost the R-value of a 2 x 4 stud wall by adding Owens Corning FOAMULAR® insulation as sheathing on either the inside or outside face of the studs. Placement will depend on which side of the wall is opened.