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Indoor air quality and fiberglass insulation

user-1062744 | Posted in Green Products and Materials on

Hi, two questions if someone can help me out:

1. Is formaldehyde an issue in all types of fiberglass insulation (ie, batts and loose-fill), or just in batts? In other words, if I am doing loose-fill insulation should I look for a formaldehyde free type or is all loose-fill free of formaldehyde? I ask because I see batts advertised as formaldehyde free but not loose fill (for example, the new Owens Corning formaldehyde free line only appears to be for batts).

2. Is there an advantage to using batts over loose-fill for indoor air quality concerns? Just seems like the loose-fill insulation gets everywhere is is more easily disbursed into the air.


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  1. GBA Editor
    Martin Holladay | | #1

    Johns Manville, the best-known manufacturer of formaldehyde-free fiberglass insulation products, makes both fiberglass batts and blown-in fiberglass insulation that the company touts as formaldehyde free.

    Among the products listed in its "formaldehyde-free" brochure is JM Spider, a blown-in product:

    2. If you build your walls and ceilings with attention to air tightness -- something that is certainly important anyway if you want an energy-efficient house -- then there isn't any reason that the fibers in your walls or ceiling will be mixing with your indoor air.

  2. lance_p | | #2

    Dragging up an older thread for my specific application to see if there's any new information worthwhile considering.

    We are building a new home and have a 2.5" deep service cavity on the inside of our vapor retarder layer. I'm planning to fill this cavity with R12 fiberglass batts once the electrical and plumbing are complete, before drywall. As such, the batts will be "inside" the house (inside the vapor retarder).

    Are there any Indoor Air Quality (IAQ) concerns with having fiberglass batts installed this way? Once installed they will not be disturbed, but I was wondering if modern (i.e. 2019) fiberglass batt products have any contents to be concerned about? Are all fiberglass batts now formaldehyde-free, or do I need to shop for specific products? Are there other ingredients in fiberglass batts to be concerned about?


  3. Expert Member
    BILL WICHERS | | #3

    If you install your drywall in an airtight manner you have an air barrier between your service cavity and the indoor air. That would limit any chance of compounds in the insulation getting into your interior air.

    Other options to consider would be using mineral wool in your service cavity instead of fiberglass. The “sound proofing” versions of mineral wool are a little thinner than regular batts which might be an advantage if you’re not building a 3.5” width service cavity.

    Another option is Owens Corning’s “pure safety” fiberglass insulation which is manufactured specifically to address the kinds of concerns you have. Although it’s not stocked the way it was a few years ago, I did contact Owens Corning a few months ago and they were interested to help me buy the product so it is apparently still available.


    1. lance_p | | #4

      I always have trouble picturing drywall as an air-tight barrier to anything long-term, but in this case it would only be required to keep bulk airflow out of the insulation for the purpose of not transferring undesirable compounds into the house air. I'm probably OK with that.

      Yes, mineral wool might be tough to compress into a 2.5" cavity. I'll have a look around for the Pure Safety fiberglass and see what I find. Thanks Bill!

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