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GZDZ · Oct 22, 2007, 07:22 AM

I just had the roof and plywood replaced over a 1950s addition. I exposed the rafters in the ceiling below. My question is, after I insulate with 6 1/2 kraft faced, what can I use for a vapor barrier, between insulation and sheetrock?

ballengerb1 · Oct 22, 2007, 08:52 AM

You can purcahse insulation that has a vapor barrier attached that is much better than kraft paper. If its already up there you can staple a sheet of 6 mil visqueen plastic to the rafters before reinstalling the drywall. You can find rolls of visqueen near the paint department in most home centers, frequently used as a drop cloth. What are the dimensions of your rafters, 2x10 ?

GZDZ · Oct 23, 2007, 04:57 AM

Originally Posted by ballengerb1

You can purcahse insulation that has a vapor barrier attached that is much better than kraft paper. If its already up there you can staple a sheet of 6 mil visqueen plastic to the rafters before reinstalling the drywall. You can find rolls of visqueen near the paint department in most home centers, frequently used as a drop cloth. What are the dimensions of your rafters, 2x10 ?

2x10 tappered down to 2x4 on top to pitch the flat roof. What I cannot find is fiberglass w/ foil faced, insulation. 30 years ago it was every where?? Do you know if it is still available?

KBC · Oct 23, 2007, 05:56 AM

I have used it in the past 3 years,not in loose bats,but in sheet form,(polyisocyanurate).

With an R7 per inch(or so) this is far superior to standard loose insulation(if you can find it in factory seconds, it's a great savings too)

My entire converted barn and workshop is insulated with this too.

Another application(although you have already installed the roof,I believe) is called NAILLINE,it is a sandwiched insulation board between OSB sheets,made for exactly your purpose(exposed beams)

Good luck,Hope this helps,

Ken

ballengerb1 · Oct 23, 2007, 08:58 AM

Foil faced insulation has been replaced with what looks like kraft paper. However, if you read the spec on the kraft paper insulation you will see that it now has a vapor barrier in it, not just paper any more.

beez71 · Jan 29, 2008, 12:17 PM

Be careful as to not OVER INSULATE your ceiling. Make sure to leave some space between the insulation and roof deck. All roofs need ventilation. No ventilation will lead to dry rot which I see on a weekly basis.

BrunoM · Mar 8, 2011, 06:20 PM

L checked out warm flat roof type and the advise l get is that since the insulation is now on top of the roof deck, there is no need for ventilation . Any advise on this ,since l am about to start mine as soon as weather is right . Thanks Bruno

GZDZ · Mar 10, 2011, 10:01 AM

I used the 2'x16" , corrugated styrofoam, stapled to the wood above the insulation to allow some air movement between the wood and the fiberglass.