Insulating garage ceiling

Here is what I plan on doing with my garage ceiling and am looking for any advice anyone can give me. There is a bedroom above the garage, and the garage ceiling is 14" engineered joists. I have drilled a couple of test holes in the garage ceiling to see what is up there, and there is a good amount of batt insulation above the drwyall with the paper facing up. I am going to drill a hole at each end and the middle of each joist space and blow in cellulose to each cavity both directions. By sticking my hand up there and moving the batt to the side, I can put the hose in to blow it above the paper and fill the rest of the cavity. There are 2 exteriror walls on the garage, and I plan on making sure insulation gets packed in very well on those two areas which is probably where the cold air is coming in from anyway and traveling down the joists above the insulation. It should move along easily since the paper side is up, and fill the remaining space above the batt insulation. Simply put the circles back in place from drilling them with a hole saw and patch them up. This should add additional protection from cold air in the garage, and should also solve the problem of cold air moving down the joists areas. I know others who have done this with great success. Any thoughts or suggestions?

Welcome to the site. Just so you know the paper side of the insulation should be next to the warm area, and wasn't needed because the floor works as a bearier. Your plan seems reasonable but you never want to stuff insulation. It wants to be fluffy.

Without tearing down the garage ceiling and having to re-drywall it, I don't see that I have much choice. I am considering just doing the parts of the ceiling that are along the outside walls of the house, that has to be where the cold air is coming in that is running down the joist areas. The bedroom above it is about 15 degrees colder than the rest of the house, and the bedroom floor (carpet) is ice cold as well. The insulation that is there in the garage ceiling now seems to be all right, seems to be about 10" thick in the 14" space, but there is cold air coming in from the 2 exterior walls somewhere that is traveling down the joist spaces. Any other thoughts? If I blow in insulation in to the last 3 feet of the joist space on the ends along one of the exterior wall, and then also the full space along the other wall (the wall that runs parallel with the joists), then I think that will prevent any cold air from coming in where they did not do it properly. That way I don't have to patch as many holes, and use more material. Thoughts?

I think you are right about the ends being the problem. they should have stood the insulation on edge against the outside wall and then flat against the floor. If they didn't do that and if the insulation settled a little, you have no value left. The other thing to think about is, the floor is the hardest to heat as the heat in the room wants to rise and the insulation will only hold the heat that is there.
So if the floor is cold or has no heat, insulation will give little help.