# Blow insulation OVER attic floor?



## gregzoll (Dec 25, 2006)

You are going to have to rip up all of that flooring, then figure out how to re-frame, so that you have the space for R-50 or R-60. Basically means that to do it correct, you can no longer use that as a storage space in order to get the proper fill levels for insulation.


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## Fix'n it (Mar 12, 2012)

gregzoll said:


> re-frame, so that you have the space for R-50 or R-60.


re frame what ?


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## joecaption (Nov 30, 2011)

Plywood has to go, I agree, what framing?
Before doing it air seal everything that comes through the tops of the walls and the ceiling with expanding foam.
Add foam or plastic baffles so the soffit vents do not get blocked with insulation.


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## gregzoll (Dec 25, 2006)

Fix'n it said:


> re frame what ?


Reframe if they wish to use as storage.


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## Garblefarf (Jan 16, 2013)

Once again, it will not be used for storage. My main question is, what harm is there in leaving the plywood there?


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## joecaption (Nov 30, 2011)

It may act as a vaper barrier and cause mold to form.


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## HomeSealed (Jan 3, 2008)

The only way that it would make any sense to leave the plywood would be if it was secured already. You'd then dense pack underneath and blow over it. If it is loose, hire some kid to come pull it all out so that you can add insulation effectively. As Joe mentioned, this would also be the time for proper air sealing up there. Also as mentioned, you'll want to add baffles down to the soffit vents and install dams to prevent wind-wash and/or all of your loose-fill insulation from falling down into the soffit.


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## AllanJ (Nov 24, 2007)

Somehow I do not think that leaving the plywood there would cause a vapor barrier or moisture problem. Just do not add an additional moisture barrier.

Do not stuff more insulation under the plywood so as to compress either the new insulation or existing insulation significantly. That will actually reduce the R value a tad.


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## joecaption (Nov 30, 2011)

Also if it really is only 3/8 I sure would not be doing any walking on it. It's to thin for that.


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## HomeSealed (Jan 3, 2008)

AllanJ said:


> Do not stuff more insulation under the plywood so as to compress either the new insulation or existing insulation significantly. That will actually reduce the R value a tad.


That statement requires some extra clarification. Dense packing cellulose will not reduce R-value of the space, nor will it for blown fiberglass that is designed for dense packing. It will increase the R value and slow airflow as well... That said, you don't want to crush batts of fiberglass or regular loose fill.


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