Old attic insulation looks like laundry soap ???

napagirlOctober 26, 2011

Need help identifying what this is - hope it's not hazardous!

We just discovered that our 1953 California rental house has some kind of white granular insulation between some of the ceiling joists. Most of the insulation is old fiberglass batts. But in some places the batts were removed and replaced with this substance. It totally reminds me of white powered laundry soap, only much lighter and very white. It was not blown in, but poured into each bay. A previous owner must have done it sometime between 1953 and 1970. I've done some research and it is not vermiculite, which sometimes may contain asbestos.

We want to add more insulation, but at this point we're not sure whether it will be DIY fiberglass batts, or blown in fiberglass. The white substance covers approx 200 sf at the far end of the 900 sf attic. I'd really like to know what it is, if its hazardous, and if it should, or could, be removed.

Thanks in advance for your help.

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Hi. It sounds like perlite to me. If the prior owner had any relationship with the masonary industry, it is even more likely, as perlite was commonly used to fill the cores of cement blocks. You can google it to find photos/info. I believe I've read that it is not hazardous, but I'd certainly spend a few buck to have it tested.
Good luck.

    Bookmark   October 26, 2011 at 3:54PM
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it is a glass frit formed by heating the raw material until the water in it increase the volume by many times.

It is stable and non flammable, and can act as insulation.

    Bookmark   October 26, 2011 at 3:57PM
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Although not containing asbestos like vermiculite sometimes does, perlite is also very dusty and the dust can cause breathing problems if you inhale much of it. Dust masks are advisable if you have to interact with it much.


    Bookmark   October 27, 2011 at 1:09AM
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Thanks for all your responses. Since its at the far end of the attic over the bedrooms I think we'll just leave it. DH did try to burn some of it with negative results, so that's good!

    Bookmark   October 30, 2011 at 11:56PM
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My 1912 bungalow had gypsum powder poured between the attic joist as "insulation". Although the empty bags were still in the attic, I still had it tested to verify. The gypsum was dumped in up to the depth of the joist. It did not create any issues until you add to do maintenance in the attic. What a PITA to deal with.

I finally had it dealing with this stuff when I had to do some ceiling repair. I paid an insulation company a few hundred bucks to come out with their industrial vacuum and suck the stuff out. I am happy the is gone.

    Bookmark   October 31, 2011 at 10:49AM
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