Insulation help for my garage with pics

That's what all the experts have told me. If you fill the cavity, and vapor barrier no ventilation is required. I know it sounds wierd, but if you stop the warm moist interior air from getting into the wall and condensating then there's nothing to ventilate. If you think about it, you don't ventilate the walls, they're filled with insul, and vapor barrier. It's all about the interior moisture, not the exterior moisture. The exterior moisture is kept out by the roof, and the siding assemblies, tar paper, tyvek, shingles, siding, cualking, etc...

If I wanted to insulate the ceiling of my shop I would sheetrock the ceiling, installed unfaced fiberglass insul above, and ventilate the attic space. Install the insul as you sheetrock. Just lay it on top. Or you can have a insulation complany come in and install blow in insulation which is just ground up fiberglass. they'll probably blow in about 12 inches, and it would cover everything, very efficient. No warm side vapor barrier would be needed because any moisture that got through from the warm side is ventilated out through the attic vents. If you still want to be able to store stuff above install an attic access ladder from Lowes,or Home depot, the kind that folds down. Be careful not to put to much up there because the trusses weren't design to carry a strorage load. Also don't forget the walls, no sense doing the ceiling if you don't do the walls. Doors, windows? You want to create a complete thermal envelope. Then you'll be toasty warm when your workin' on the toys...