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What is the best R-value for loose blown cellulose

Bruce Chyka | Posted in Green Products and Materials on

I have a cellulose manufacturer that claims their product has a rating of R-3.65 per inch. Can’t determine who tested it. I have an old DOE sheet that provides a range of 2.5 to 3.0 and recommends using a 2.8 value. I think the builder may be getting jobbed as the installer has assign an R-38 to 10.3″ of product blown in.

Was there some advance I’m not aware of in the cellulose industry??

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  1. Riversong | | #1

    The old specs are for loosely blown or loose fill cellulose, when inexpensive machines were used for retrofit applications.

    Today's cellulose offers R-3.4/inch for attic loose fill, and R-3.8/inch for dense-pack in a closed cavity at 3-3.5 pcf density.

    Be sure to use cellulose that has only borates as fire retardant. Some cheaper material uses ammonium sulfate which can off-gas and is corrosive to metal if it gets damp (like the Chinese drywall).

    The quality of the installation is key, as for any insulation system. I would avoid the damp spray cellulose, as that adds unnecessary moisture to the wall assembly in addition to the 600 gallons of water that has to dry out of the KD lumber framing in the first heating season in a typical house.

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