If your garage is 45 degrees and you have a bonus room heated to 72 degrees above the garage the vapor retarder faces the upstairs room.
Garage attic insulation vapor barrier.
If you need a vapor barrier and your insulation is unfaced you must cover it with a polyethylene film.
You don t mention whether there is a bonus room or living space above the garage.
Vapour barrier is on the top of the rafter then insul then board if heating garage insul vapour then board need hatch for summer to let out hot air i m a insulator typar is a better product in a.
The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.
In cold climates a vapor barrier is almost always needed.
Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case.
After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.
This acts as a barrier to keep heated moist air from rising up into the attic during cold weather.
Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers.
If you are not sure if you need insulation in your walls follow along with this flow chart.
The classic answer is that the vapor barrier goes on the warm in winter side of the assembly.
The facing on faced insulation acts as a vapor retarder.
In mixed climate areas the vapor barrier is optional depending on the total design of a building.