W. J. writes from Mobile, Alabama: "I have about 2 inches of blown-in loose insulation (cellulose?) in my attic. In adding more insulation, (1) would it be best to blow in more cellulose, or (2) can I put fiberglass bats over the existing loose insulation? If so, (3) I think the fiberglass should be unfaced. Right? (4) If fiberglass is ok, I think I should use 6" unfaced. Right? (5) Does anyone make 3" or 4" unfaced fiberglass bats for attics--I think the spacing is 24" between attic 2x4s? (6) If 3 or 4" x 23" is made, how much less effective would it be compared to 6"? Also, what is knob and tube wiring and how can I recognize it?"

Answer: 1) Owens Corning does not make the product you ask about and I am partial to PINK fiberglass insulation so I do not recommend the option you ask about in your first question. 2) Yes you can. 3) Use unfaced fiberglass insulation. 4) The thickness depends on what R-value they want to achieve. 5) R-11, R-13 and R 15 insulation are all made for 2x4 construction. They can also be used in the attic. 6) The higher the R-value the greater the resistance to heat loss. 7) Look for ceramic knobs or tubes in which the wire gets attached to, or passes through, at the joists or studs.