Expert: Ted Barnhill (Principal, Design45 LLC) - 3/25/2010

Question
I live in Minnesota.  I have an attached three stall garage that is completely sheet rocked.  I currently 'think' the walls are insulated, but KNOW that the ceiling is not.  There is also no vapor barrier under the ceiling's sheet rock.

I would like to insulate the ceiling, just to help moderate the temp in the garage (cooler in summer, warmer in winter).  At the moment, I do not plan to heat the garage.

Question:  Do I need to add a vapor barrier of some sort?  Or can I just blow in a few inches of loose insulation?  any ideas would be appreciated.

thanks!

Answer
Ted,
I would recommend that you provide a vapor retarder in your ceiling and wall assemblies when you insulate the ceiling.  Even though the space is unheated, it will be warmed by both the ground and the house, so there is the potential for condensation within the walls and ceiling from the somewhat more humid and warm air in the garage.

The good news is that this can be achieved simply by applying a vapor barrier paint (less than 1 perm rating) and sealing all openings/cracks/boxes with caulk or foam.

Best of luck tempering your garage.

Ted Barnhill
Design 45, LLC