I’m building a new home in Northern Wisconsin. I have insulated the ceiling with kraft faced batts. The majority of the builders in this area also apply a plastic vapor barrier over the kraft facing. The insulation manufacturer doesn’t recommend it. Has any one any experience or problems doing this?
Thanks for your comments, Roger
Replies
Roger,
For a VB I'd give poly the nod over the kraft facing on the FG batts. As an aside, kraft-faced batts are almost NEVER installed correctly. If not using cells, I use unfaced FG batts with poly.
If you want to go with poly, simply take a utility knife and slash the kraft facing on the FG insulation. You don't need to make mince meat out of it...a few slashes to the paper will do the trick. Then staple the poly to the face of the framing.
When using a poly VB on ceilings do you do anything different when hanging rock, since it can't be glued?
Nope. Nothing fancy at all.
The poly simply gets stapled to the joists in the field, but I do run a bead of caulk on framing members around the edges of the poly sheet and press the poly into the caulk, then staple through the poly/caulk and into the framing. Wherever the poly overlaps another run of poly, I also run a bead of caulk and mash, then staple through both layers into framing as well.
Nothing scientific, just trying to seal the poly and get a tight envelope.
The gypsum board is screwed per code.
If you're strapping the ceiling, the poly can be put on the joists, then the strapping over the poly. Then you can glue and screw the gypsum into the strapping if you desire.
Look at page 2 of this attached document under Framing then under Cathedral Ceilings, this should help answer your question.
Bay Shore Building & Design, Inc.
http://bsbad.tripod.com
Thanks for the CertainTeed specification sheet. That's the confirmation I was looking for. It is a common practice for cathedral ceilings in Nothern Wisconsin, but I couldn't fine anything in print.
If you make diagonal slices in the kraftpaper from stud to stud or joist to joist leaving a small amount left uncut on the ends of the cut it will minimize the resulting bulge of fiberglass and make it easier to place the poly.
Half of good living is staying out of bad situations.