HOW TO INSULATE CANTILEVER BEDROOM INTO GARAGE

QUESTION FROM KATHY, GLEN ELLYN, IL

I have an unheated garage with portions of a second floor bedroom cantilever into the garage "attic" area. The bedroom is always cold near the cantilevered wall. We have already air sealed where we could access and wondered if it would help to lay unfaced insulation between the ceiling joists of the garage ceiling which is drywalled. 

There isn't any ventilation or airflow in the enclosed garage attic area eg. Soffit or roof vents. Would we need to add any type of roof vent prevent moisture problems.

ANSWER FROM THE INSULATION DOCTOR:

Good Morning Kathy,
 
First of all you are correct in adding roof vents to the garage ceiling.  

Regarding laying insulation on the ceiling of the garage, I would recommend that you do that only where the bedroom floor cantilevers over the garage.  

Then I would recommend that you install 3-1/2" unfaced (no kraft paper or foil backing on it) fiberglass blanket-type insulation on the bedroom outside walls extending into the garage, from the top of the wall down to the top of the ceiling of the garage.  The easiest method to do this, without causing damage to your drywall on the opposite side of the outside wall, would be to mark the studs, then screw a 1"x3" board to the outside wall horizontally about 3" to 4" down from the top.  Now you can install the insulation by stapling it at the top to the face of the 1"x3" board and draping the insulation downward.  If you find the insulation pulling away from the 1"x3" you may have to install a second 1"x3" over the insulation and screw it to the first 1"x3".  This will sandwich the insulation at the top and not allow it to pull away.

Hope this helps.
 
Bruce Jones
The Insulation Doctor