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Is paper-backed fiberglass enough vapor barrier?


jar240's Avatar
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Join Date: Aug 2006
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08-29-06, 09:45 AM   #1  
Is paper-backed fiberglass enough vapor barrier?

I'm in Ottawa, ON, CANADA. It gets cold here in Winter! ;-)

Our bungalow has loads of attic space, and I'd like to add more insulation on top of the single layer of paper-backed 6" fiberglas that's currently up there between the joists against the single layer of sheetrock of the celing for the livign space below. There's no plastic vapour barrier.

My question is, is this enough of a vapour barrier?

Thanks,
Chris

 
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Concretemasonry's Avatar
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08-29-06, 10:49 AM   #2  
Is paper-backed fiberglass enough vapor barrier?

I assume the paper is on the warm side of the ceiling insulation.

If you have not had a moisture problem, your existing installation must have been functioning as a vapor barrier. There is nothing like an absolute vapor barrier - only a range depending on the materials and the installation.

You can put batts (at 90 degrees to joists) or blow in cellulose(preferred) over your existing insulation.

If you try to use some of the attic space for storage, you will have a problem if the insulation is compressed.

Dick

 
jar240's Avatar
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08-29-06, 11:11 AM   #3  
Yep, its paper side is toward the warm space.

I can't see any moisture problems, and the current stuff is in-tact, not mouldy, but somewhat compressed and a little dusty.

My biggest fear in this 50-year-old house is spending the money on cellulose, only to have to pull it all up later and gut with current vapour barrier materials because this paper-backing turned out to be insufficient. In fact, this is the problem I have with any renovations other than an entire gutting to update to modern standards

Thanks, yours was a very informative reply.

If I go the cellulose route, do I need to install some sort of "edging" near the soffits to prevent the cellulose from blocking attic ventilation airflow?

Chris

 
Concretemasonry's Avatar
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08-29-06, 12:35 PM   #4  
Is paper-backed fiberglass enough vapor barrier?

Good point on the venting -

If you add insulation(fiberglass or cellulose) thickness, you could possibly block the soffit vents depending on your overhang and pitch. Use the "chutes" or troughs available at ther big boxes to maintain air flow and ventilation.

Dick

 
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