Attic Insulation over old fiber ceiling tiles

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Old 09-28-07, 12:18 PM
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Attic Insulation over old fiber ceiling tiles

I need to insulate a house in northern minnesota. Currently have 6" ceiling joists with 16" square fiber tiles stapled below for the ceiling. There is no insulation. I believe I should have batt insulation with a vapor barrier at the bottom (directly above the square tiles). But how do I install and get any kind of seal on the vapor barrier? Should I lay in a sheet of 2 mil plastic first, draping it down into the space between joists, and then installing batts with no barrier?
 
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Old 09-29-07, 10:32 PM
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Originally Posted by lakeside44 View Post
Should I lay in a sheet of 2 mil plastic first, draping it down into the space between joists, and then installing batts with no barrier?
If you follow this your attic will leak conditioned air like a sieve killing your wallet and your hard work. Since theres nothing up there right now you have a real chance to do it right. First think only about draft blocking/air sealling. If you dont stop the air from getting to the attic through your ceiling no amount of fiberglass insulation will do any good. Here is what I would do:
1. Use foam sealant (either with a good foam insulation gun or a bunch of single use great stuff cans from home depot) and seal all the joists in your attic to the ceiling tiles. THis way you stop air from leaking. Foam all penetreations thru the attic as well like bathroom vents and fans. If you have recessed lighting seal those too but be careful cause depending on the type you have to keep any insulation back cause they get hot. Just build a foam box around them using fiberboard and foam. Next seal off the flue from your fireplace using fire rated caulking. Pay attention to any interior wall top plates and block them off too using pink foamboard and more foam sealer.
2. Once thats all done you can lay in your R19 batts in each joist bay with the paper side facing towards the living space. That is your vapor barrier. Make sure you dont cover up the soffit vents if you have them though.
3. Since you are in MN you need i think R49 total insulation for your attic so then I would blow in the right amount of cellulose (about 9.3 inches) all over the batt insulation to achieve R49. Again if you have soffit vents use baffles purchased at HD and staaple them at the bottom of the eves to keep the cellulose from covering them up.
good luck
 
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