I want to insulate the ceiling in my garage. When the house was built 10 years ago, the walls attached to the house were done, and the ceiling was drywalled (Fire code). However, they did not put a vapor barrier, before drywalling. I live in Canada. Winter is about six, seven months long. I have access to above the garage. Should I staple a vapor barrier over the joices, and in between, then put my insulation?
I just want to be able to work in there once in a while, over the winter. I already put vapor barrier and insulated the outside walls. Going to heat it with a couple of ceramic heaters. The roof is well ventilated, with soffit vents, and a whirlybird. The roof is made with 2x4 trusses on two foot centres, and they used metal channeling to screw the drywall to.

No vapor barrier.