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Cellulose Insulation … Specifications and Downsides

homedesign | Posted in Energy Efficiency and Durability on

I have seen specifications for cellulose installation and mention of “cautions or downsides” scattered through some of the threads here at GBA.

Just trying to consolidate some thoughts here.


Should we really avoid recycled newsprint?
If more people decided to jump on the Cellulose train….
Seems like there would not be enough of the “clean” production scraps that Robert Riversong has mentioned.

Which additives are safe and necessary and which to avoid?

On example of a warning is in Dr Joe’s “Don’t be Dense” paper……
Do not use cellulose(alone) in an unvented roof.
That one should be easy to overcome…..

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  1. Allan Edwards | | #1

    If you want an unvented attic, how do you install cellulose between rafters from plate to ridge and be assured you are getting a tight application that will remian that way.

  2. 5C8rvfuWev | | #2

    > If more people decided to jump on the Cellulose train.

    Not to mention that newspaper readership and publishers are dropping like flies.

  3. homedesign | | #3

    Lstiburek offers a couple of suggested methods at the end of this paper...

    I will still say "why bother" ...
    just do not create conditioned attics and or do not design unvented cathedral ceilings.

  4. homedesign | | #4

    I have heard this comment before about reduced newspaper demand.
    I have quit the hard copy newspaper and magazines.

  5. AyTGxzTyGS | | #5

    "If more people decided to jump on the Cellulose train...."

    Great! If we can reduce the flow of paper to the landfill to zero, we're doing something right.
    Will there be enough cellulose for everyone everywhere to use? Probably not, but so what?
    That just means that cellulose is not the "magic bullet"solution either, and the sooner we stop looking for a one-size-fits-all solution, the sooner we can get on with the work of taking an honest look at our housing needs and building context-sensitive, climate-responsive shelters.

  6. homedesign | | #6

    I thought you only used "fresh" paper cellulose that came directly from the offcuts and waste at the newspaper printing facility.
    maybe I remembered wrong?

  7. Riversong | | #7

    The US waste stream is 30% paper by volume and 35% paper by weight. As much as 14.4% of landfill volume is newspaper - the largest single contributor by either weight or volume. Only about 25% of all paper is recycled in the US. Newspaper in landfills produces methane gas, 20 times more powerful than CO2 in producing global warming.

    There is little likelihood of the cellulose insulation industry running out of source material any time soon. While a smaller percentage of Gen X and Gen Y people read newspapers than Boomers, the decline in readership is mostly among the Boomers, with younger people remaining relatively stable in their reading habits.

    As for additives, borate compounds are the best for fire retardancy. They bond to the cellulose and do not wash out over time, are non-toxic to humans and pets but toxic to all common household insects and an irritant to rodents. Some manufacturers also add an EPA-approved borate fungicide. Ammonium sulfate is a less expensive fire retardant that can cause metal corrosion when wet and has been known to offgas like the Chinese drywall - it should be avoided.

    While vented roofs are almost always preferable, there are tens of thousands of unvented roofs with cellulose insulation and no record of failure. Cellulose is better than any other insulation material in absorbing and redistributing moisture with no loss of R-value and has the unique ability to store up to 30% of its weight in water reversibly while protecting wood framing from excess moisture concentration.

  8. 2tePuaao2B | | #8

    Good thread John. Thanks

  9. Riversong | | #9

    Well, I certainly don't use insulation made from used toilet paper.

    From National Fiber:

    "Cel-Pak is made primarily from over-issue newsprint, along with other high-quality over-issue paper sources, and carefully selected post-consumer newsprint, typically from paper drives. As just one example, if a New England newspaper printed 1,000,000 copies yesterday, but only sold 750,000, National Fiber buys the remaining 250,000 in bulk and turns them into insulation."

    And re-purposing newsprint is far more "green" than recycling it into new paper, which requires some virgin wood pulp, some additional bleach, and about 30% of the energy input of new paper.

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