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.

  • 1
    What's below? Which way is the fiberglass (above or below the kraft paper)? The garage is below this, I gather? – Bryce Jan 16 '14 at 3:02
  • The insulation side is against the garage ceiling the kraft side is approx four inches from the bedroom floor. So the space I need to insulate will be on the warm side of the kraft paper. Not sure which material type to blow in. Fiberglass or cellulose – user19278 Jan 17 '14 at 3:37

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.

  • You mentioned cellulose what about fiberglass. There is also a white insulation that looks like cotton. I don't remember the or products name – user19278 Jan 17 '14 at 3:49
  • 2
    Fiberglass does not block air or moisture movement nearly as well as cellulose. – Ecnerwal Jan 18 '14 at 1:52

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