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4mill poly sheet to hold up fiberglass inulation

2282 Views 7 Replies 6 Participants Last post by  Gary in WA
My inspection department told me i have to insulate the house and pass that inspection before installing any drywall.

I want to staple 4mil poly sheet to the cieling on my single level home to hold up the rolled in insulation.

Is 4 mill enough? What size and frequency of staples should i use?
I have 16oc joists for my attic/cieling.

Its gonna get cold soon and my furnace will blow up so i want to get this going.
Any concerns anybody can tell me? thx allot fo any help.
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The poly is just a vaper barrier, not to hold up the insulation. Do not install the insulation until the sheetrock is up.
Joe missed this part...
My inspection department told me i have to insulate the house and pass that inspection before installing any drywall.

What about securing the insulation with insulation supports?
i don't think a vapor barrier is necessarily a good idea in chicago. why do you feel you need it? if the insulation (i assume fiberglass??) is loose, i would never try to hold it w/ 4 mil. i think, if something is needed, tyvek would be a better choice; it is far tougher and much more vapor permeable. if you don't HAVE to have some kind of sheet stuff, i'd suggest air sealing using the airtight drywall approach. that will require that all electrical boxes, light boxes, etc, be air tight as well. etc.
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Don't like poly as a vapor barrier either.

Get the insulation hold ups or use and insulation like Roxul that doesn't need it.

Like JKlingel said, make the drywall airtight.
For your Zone 5, either a vapor barrier (poly) or vapor retarder (asphalt-coated paper faced is acceptable per minimum code to meet the 1/300 NFVA for attics;

Notice; meeting the 1/150 rule doesn't require a vapor barrier/retarder (if the venting is correct).

Ask your local AHJ if poly is required or is that something you are suggesting? The 2012 Code changes to Zone 6-8 only for minimum venting/vent placement/retarder/barrier required;

From Building Science;
"In addition to an air barrier at the ceiling line, a Class II vapor retarder (see sidebar) should be installed in Climate Zones 6 or higher (see Map 1).
Class I vapor retarders (i.e. vapor barriers – see sidebar) can be installed in vented attic assemblies in Climate Zones 6 or higher (see Map 1) but should be avoided in other climate zones as top side condensation can occur in summer months during air conditioning periods." From;

I'd rather see Tyvek over the insulation, but not if you air-seal the attic first. Don't leave air pockets/cavities under the insulation after installing drywall ceiling from the wires, the insulation requires contact with drywall. Ask them if you can use unfaced batts after drywall, many departments do. They can check at final inspection.

PS. A good read;
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