Bought a home that was built in the late 1920s. Was checking around the attic when I saw "Johns-Manville Super Felt" insulation. Upon some research there seems to be contradicting information on whether this brand of insulation contains asbestos or not.

home attic insulation rock wool

The ELG Law and Asbestos.com websites list Super Felt as part of the product line that has asbestos.

However, someone else at Inspectapedia.com cites research saying that rock wool generally does not contain asbestos and it is unlikely that this product line had it either. Since ACM insulation usually came in loose-fill or board format, not batts.

I realize the surefire way is to get a sample and have it tested. However, given that it seems to be largely intact and tearing a piece off would make it friable, I'd love some thoughts on how best to proceed.

  • 4
    Send a sample for testing. No other definitive solution. What else did you expect? Based on your research...
    – Solar Mike
    Sep 13, 2021 at 6:09
  • I was hoping someone else had already safely gotten it tested and could post their experience.
    – najm
    Sep 13, 2021 at 11:30
  • 1
    It's likely that the "recipe" and manufacturing processes may have changed over the years. You might try contacting Johns-Manville to learn what they have to say about their product, but the only way to know for sure if there is asbestos in your insulation is to test your insulation. I'm not sure I'd trust lawyers or "industry groups" to have accurate information as they may have a vested interest in perpetuating your uncertainty and doubt. Removing a small sample for testing isn't likely to result in significant contamination if you're careful about disturbing it as little as possible.
    – gnicko
    Sep 13, 2021 at 12:27
  • 3
    I’m voting to close this question because questions about asbestos identification are off-topic
    – Machavity
    Sep 13, 2021 at 13:34
  • 1
    I was hoping someone else had already safely gotten it tested and could post their experience ... why would a test result at another location have any bearing on your test results?
    – jsotola
    Sep 13, 2021 at 14:41

1 Answer 1


Unfortunately some old products from Johns Manville did contain asbestos . But repeating comments , the only way to know is to have it tested.

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