On Top Of An Attic Floor

 
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Old 10-21-2010, 06:08 PM   #1
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On Top Of An Attic Floor


I have an older rental house that I'd like to ad a little attic insulation to. Most of the attic is covered with plywood. Would it be effective for me to roll fiberglass insulation over top of the plywood, or would I have to tear out the floor and go between the joists?
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Old 10-21-2010, 08:19 PM   #2
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Re: On Top Of An Attic Floor


As long as you're confident that there's no airflow beneath the plywood, there would only be a tiny loss in efficacy by putting the insulation on top, probably not enough to warrant the labor involved in tearing it up. The only issue I could see is that you are potentially dealing with two vapor barriers, if there is one beneath the plywood. The plywood of course would form the second barrier.

In either case, I would use unfaced insulation.

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Old 10-21-2010, 10:41 PM   #3
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Re: On Top Of An Attic Floor


unfaced insulation, and lay it out the opposite way of the studs as opposed to the same direction...just cuts out the seams...also, airseal whatever you possibly can, because if you add all the r-value with no airsealing, you aren't going to see much return
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Old 10-22-2010, 09:23 PM   #4
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Re: On Top Of An Attic Floor


Thanks, you've been very helpful.
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Old 12-12-2010, 11:28 PM   #5
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Re: On Top Of An Attic Floor


Why not dense pack with cellulose?. Unless the attic has knob & tube wiring.
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Old 02-07-2011, 02:33 PM   #6
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Re: On Top Of An Attic Floor


Installing insulation over the decking is okay. Loose-fill fiberglass is the best insulator for attic floors. Unlike batt insulation, loose-fill doesn't leave any gaps and forms a seamless blanket over the entire attic. Its also much less expensive per R (r-value) to install blown fiberglass. As far as other types of blown-in, consider that cellulose is recycled newspaper with fire-retardant chemical sprayed on it... these chemicals can corrode wiring over time. Hope this helps!

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