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Community and Q&A

I am planning to re-insulate my attic

Sharon Hawthorne | Posted in Energy Efficiency and Durability on

I’m located in Northern California, Sonoma County. I am planning to re-insulate my attic after (Step1) removing all the old blown-in cellulose (due to contamination from a rat infestation, factors contributing to this problem assumed to have been rectified).

I am disinclined to use fiberglass batt insulation due to its not filling voids well around framing members, electrical receptacles, and vent pipes, but have concern about the stability of a blown-in product in the airy atmosphere of this particular attic and the efficacy of blowing in when the roof edge is an open-ended tile. But I also find spray foam products objectionable due to ingredients and concern about their ability to release any moisture that might intrude behind.

I don’t want to incite a brouhaha such as the article about the insulation job gone wrong, did but would like to hear opinions of folks experienced with this sort of roof system in this climate.

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  1. John Klingel | | #1

    Sharon: It sounds like you have psychologically eliminated almost any type of insulation. Perhaps if you clarify what "opened ended tile" is, someone could take a better stab at helping than I can. I think your concern about cellulose in an "airy atmosphere" is probably needless, though understandable. I think you'll find that the cellulose will "crust" and be pretty wind proof, and/or you can do something to slow down the hurricane over it. Curious: Was your original cellulose treated w/ borates? It should be, as rodents don't like that stuff. Good luck to ya.

  2. GBA Editor
    Martin Holladay | | #2

    Most people find that cellulose insulation performs best on attic floors, but if you want a different product, you can try blown-in fiberglass. However, be sure to install a VERY deep layer of blown-in fiberglass, since it has an R-value of only about R-2.2 per inch.

    Any insulation job requires the following steps:

    1. Install wind-wash protection at the attic perimeter, facing the soffits. You need rigid blocking (made of lumber, cardboard, or rigid foam) to prevent the insulation from spilling into the soffit. Most installations also include a ventilation chute at this location.

    2. Do a careful job of air sealing the ceiling before installing any insulation. This step is not optional.

  3. Matthew Amann | | #3

    Sharon, if you wan to choose a green insulation, and choose the appropriate material for your application, choose CELLULOSE. Of course following Martin's sound advice.

  4. Sharon Hawthorne | | #4

    Just to clarify, this roof is Mexican style (barrel shaped) concrete tiles laid on skip sheathing.with no bird stop or eave closures ---the bottom tile, next to the eave, is open ---.nothing to block air or moisture movement from passing through .... or blown insulation from being blown out during application.

  5. GBA Editor
    Martin Holladay | | #5

    First, install ventilation chutes. Then install wind-wash dams.

    Or you can use a product like AccuVent -- install both at once.

  6. Aj Builder, Upstate NY Zone 6a | | #6

    "rat infestation"

    "no bird stop or eave closures"

    First, you need heavy hardware critter proof screening, prior to any foam baffled that critters would chuckle about as they went thru it to re-infest whatever new insulation is installed.

  7. GBA Editor
    Martin Holladay | | #7

    Rats can squeeze through holes the size of a quarter, so I wouldn't want to be the contractor assigned to that job.

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