I have a bedroom above my garage. The builder insulated the floor with R13 kraft faced insulation, leaving an un-insulated space in the floor. I was thinking of blowing insulation in the empty space that is between the floor and the kraft side of the insulation to insulate this area. Will this cause a moisture problem? The garage is not heated and is finished with drywall.
Should not cause a moisture problem. Cellulose has interesting and useful properties with regards to moisture movement on the one hand, and the vapor barrier is still going to be on the warm side unless there's a lot of space.
Essentially, cellulose has been tested multiple times to have such low air movement through it that it effectively does not need a vapor barrier.
Blowing it in without tearing the Kraft face may require a good deal of care.