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Cellulose under Batts

Posted by purduephotog (My Page) on
Sun, Sep 28, 08 at 13:03

Have the first baby due in November and I'm in the process of 'upgrading' the guest bedroom to a nursery. Have added cans (IC rated, airtight), all new electrical, GFCI, and repaired the walls extensively.

I now need to make a decision in regards to insulation. The previous owners installed R-40 batts above the 1950's collapsed fiberglass- and there is no vapor barrier.

Should I:
1) Install a plastic 6 mil vapor barrier and pray I don't go thru the ceiling, staple it in place and then blow in cellulose insulation, reinstall the batts
2) Skip the vapor barrier and do as #1
3) Skip the cellulose and just roll the batts back.

No matter what I need to build some shelving up there to store all the junk, err, hobbies that I'm not into anymore- so that will go over the insulation on raised platforms.

Suggestions are most welcome- Thank you, Jason.


Follow-Up Postings:

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RE: Cellulose under Batts

Hi,
This is just me, but I would:

Pull back the batts locally, and check for any air leak paths from living area to attic -- things like wire or plumbing penetrations, light fixtures, ...
Sometimes you can spot these by the dark stains visible on the FG batts -- this is dust in the air being filtered out by the FG.

Then I would blow cellulose over the batts.
The cellulose will add R value, and (probably more importantly) will stop the convection currents that form in FG and cut its R value under cold conditions. It will also provide some additional resistance to air infiltration.

Another option might be to take the batts out altogether (maybe use them elsewhere), seal up the leaks as above, and then blow in cellulose to the R value you want.

Unless you see evidence of moisture problems up in the attic, I would not try the vapor barrier.

Gary


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