Question: Can I add a second layer of insulation in a wall?
Todd writes from Dallas: "Would using two layers of R-13 fiberglass insulation in a 2x4 stud wall, and thereby decreasing the airspace between the fibers, be more or less effective that one layer of R-13?"
Compressing insulation will reduce the R-value. If you want more R-value in a 3 1/2" cavity, I suggest using 3 1/2" high density insulation that has an R-value of 15.
