PM writes from Bay City, Texas: "I need to install hardwood flooring in a room built over a garage. The garage ceiling is insulated and sheetrocked. I have a wet (MC 20) subfloor in the room above the garage. I believe that the insulation is installed backward. How should the insulation be installed and should the garage below be ventilated?

“If a garage is completely insulated, walls & ceiling with no window and no climate controls and the insulation was installed in the ceiling with the paper face down toward the garage, what will happen in that space?"

Answer: The insulation we recommend is Kraft-faced R-19 or Kraft-faced R-25 with the facing installed toward the warm-in-winter side of the framing. The garage area does not typically have to be ventilated. However, I am not familiar with the term wet subfloor.

Fiberglas insulation is designed to slow the transfer of heat. Insulating an unheated/unconditioned space will not help with thermal control but it may help with sound control. The Kraft paper is combustible. As such it is required to be covered with a thermal barrier (such as sheetrock).