HEATED GARAGE CEILING VAPOR BARRIER
BELOW FLOOR OF ROOM ABOVE


Question from Jim from Pittsboro, NC:

Should I use a vapor barrier when insulating the floor in a room over a garage? The garage will be completely insulated and conditioned with a dedicated HVAC system. There may be times when the roll up door is left open for long periods of time and concerned about humidity in the garage affecting the room above. Thank you.

ANSWER FROM THE INSULATION DOCTOR:

Good Morning Jim,
 
Regarding your question about the vapor barrier.  Yes you will need a vapor barrier.  I am assuming you are referring to the ceiling of the garage (between the garage ceiling and the floor of the room above it).  

If you are installing a kraft-backed blanket or rolled type insulation, the kraft-backed paper will act as your vapor barrier and should be installed with kraft paper facing down toward the garage heated area.  
 
If you are using an unfaced insulation without a backing you will need to install a 4-mil visqueen vapor barrier before installing your drywall in the garage.
 
I hope this answers your question and, if not, please send me more information on what type of insulation you are installing.
 
Bruce Jones
The Insulation Doctor