Plastic as a vapor barrier attic insulation


I am about to install some batt insulation in an old ceiling where the joist placement must have been determined by the number of remaining boards on the job site. Meaning absolutely nothing is 16" CC.
I am going to use unfaced batts as they are much easier to trim to fit. Then I am thinking of using 4 mil plastic off the roll stapled to the joists for the vapor barrier. This is quite common in wall areas but I have never done or seen it in a ceiling application.
Comments. Suggestions.
Colbyt
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No problem, in fact I have seen it done a lot around here.
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On Jul 26, 7:59 pm, snipped-for-privacy@columbus.rr.com wrote:

Actually, I do see a problem. Not sure exactly how this is proposed to be installed, but from the wording, it sounds like the insulation could be going in first, followed by the vapor barrier over top? If so, that is incorrect. The vapor barrier should be against the ceiling, the insulation on top.
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Actually, I do see a problem. Not sure exactly how this is proposed to be installed, but from the wording, it sounds like the insulation could be going in first, followed by the vapor barrier over top? If so, that is incorrect. The vapor barrier should be against the ceiling, the insulation on top.
NO. Insulation in first held in place wire light wire stapled to the bottom of the joists and then plastic stapled to the room side and covered with drywall.
Spray in foam may be a good option for some installations but not his one. For all practical purposes this is the same as a cathedral ceiling. Just enough room above for a little air flow.
Colbyt
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Vapor barrier goes to the warm side...... inside in cold climates, outward in warm climates.
expanding closed cell spray foam costs more but at R6 or R7 per inch is a far superior insulation to fiberglass, seals all the little cracks etc, which saves energy and stops noise too, noise is transfered thru air passages, which dont exist with spary foam.
plus it requires no vapor barrier. its naturally one.
can get local contractor to install, joist width and obstructions meaningless..
I was told theres drums available for DIY jobs.
its a realtive of the small cans of sealing foam like great stuff.
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