I like in Central NJ and am getting ready to add insulation to my attic (there is currently none) I am planning to use the Owens Corning Atticat with fiberglass insulation for the jobI have installed baffles to not block the soffit insulation I know that I need to install a vapor barrier, but I don't know what is the correct methodI bought vapor barrier plastic in a 10' x400' rollCan I lay a big sheet of plastic over the top of the joists and then start from one side, staple down at the bottom of the joist on both sides, and then up and over the joist, and staple down on the bottom of the next joist and continue this process all the way? Is there a potential moisture issue by covering the wooden joists?
It would be better not to install the vapor barrier in your case over what you suggestedBy covering up the joists you are trapping moisture by the wood, without a good way to escapeThat is the opposite of the purpose of a vapor barrierPlus you have a vented attic space that will drain any moisture awayI suggest you make it a well vented attic space and forget the vapor barrier The vapor barrier is put in front of places where water cannot easily drain from such as walls, floors, etcSince you don't want moisture to sit on wood, it will moldAs well as it protects an unvented roof from being damaged when the vapor freezesThe best you can do with a vapor barrier without removing a finished ceiling is cut pieces to go in between the joists, they can be a bit oversizedPut a bead of silicone caulking where the joist meets the finishing material and press the edges of the plastic into the siliconeThis will limit the amount of moisture that can get into the attic, but the little that does should easily drain away as long as the attic is properly ventedThe kitchen and bathroom attic areas need this more than the other areas I honestly don't envy your choices, retrofits suck.
(Our magnificence required us to try this in a lab) We used 2 pencils for slits, a white display for the display on the distance L from the supply of sunshine, a laser beam, and a block to preserve the laser as good as a few rubber bandsJust shoot the laser by way of the slits (and bear in mind to regulate the space among the pencils by way of squeezing them clsoer in combination to detect what occurs to the sunshine which passes by way of).
