Insulating an attached garage?

[Noltz]

I accidentally posted this question in General, so my apologies for cross positing.

Short version; I want to insulate my attached 2 car garage. The exterior wall and half the roof are uninsulated and have no vapor barrier. Do I need to pull down the drywall that's there and install vapor barrier, or can I use blown-insulation directly against the drywall in the exterior wall and the uninsulated (trussed) roof? I intend to keep the garage around 5°C, warming it up when I want to go out and work.

 

[ROBZ71LM7]

Vapor barrier paint can address the walls. You typically do not have a vapor barrier in the ceilng/attic, just blow in insulation. Try to do some air sealing while you're at it, but remember overhead doors are leaky.