Cellulose insulation in the hand Pros and Cons of Cellulose Building Insulation

  • Cellulose Insulation Pros-Cons - CONTENTS: Pros-and-Cons of Blown-in Cellulose Insulation for Buildings
    • Comparison of Cellulose with Fiberglass & Rockwool Insulation
    • Photo guide to identifying & inspecting cellulose building insulation
    • Fire retardant test results on cellulose building insulation
    • Properties and R-values of different building insulation products
  • POST a QUESTION or READ FAQs about cellulose building insulation

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Cellulose building insulation advantages and disadvantages:

This article compares the features of loose-fill or blown-in cellulose building insulation with fiberglass and rock-wool loose-fill or blown-in materials.

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Pro's and Cons of Cellulose Insulation

The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

Question: How does Cellulose Insulation Stack Up Against Fiberglass or Rockwool Insulation?

I plan to retrofit 7 inches of blown insulation over the top of 6 inches of existing fiberglass insulation, and I would like to use blown-in cellulose.

How does cellulose insulation stack up against fiberglass or rockwool with respect to

  1. R-value
  2. Moisture absorption
  3. Attraction to (resistance to) nesting rodents
  4. Fire protection (fire resistance)

Thanks - David Stingle, Black Creek WI


The R-vale per inch of loosefill insulation varies depending on its installed density and product characteristics. For that reason, the most reliable way to buy loose-fill insulation is to specify the R-value - not the thickness - and install the correct number of bags per square foot, following the loose-fill or blown-in insulation coverage chart printed on all insulation bags.

The insulation chart also shows a minimum insulation thickness necessary to guarantee the desired R-value3.

The U.S. Federal Trade Commission (FTC) requires insulation manufacturers to make available to consumers an information sheet explaining this system.

Moisture absorption of cellulose insulation: Of the three insulations you named: blown-in or loose-fill cellulose, fiberglass, or rockwool, only cellulose will absorb moisture, but this is only a problem if it gets drenched, such as by roof leaks into an attic or building wall. The other two insulations will hold moisture only on their glass or mineral fiber surfaces.

Fire resistance of cellulose insulation: Of the three insulation products we are discussing, only cellulose is potentially flammable, if its fire retardant loses effectiveness over time (as some suspect of the dry-applied fire-retardants). Studies in the mid 1980's of the reliability of fire retardance of cellulose insulation over time were inconclusive.

See Cellulose Insulation Fire Resistance for details.

As for rodent resistance of cellulose insulation, we (DJF) have observed that rodents are happy tunneling in just about any soft insulating material, but we have also observed that a different sort of pest, mold, is not generally found in cellulose insulation. We (DF) believe based on our own field and lab investigations that the fire retardant chemicals used to treat cellulose insulation appear to also resist mold growth.

Mold resistance of cellulose insulation: cellulose insulation appears to be resistant to mold growth. Details are at Cellulose Insulation Mold Resistance

Watch out: other insulation properties such as air flow resistance and moisture resistance may be very important in some cases, such as choosing an insulation to use in or over a crawl space that may be damp, or against basement foundation walls - Ed. See FIBERGLASS INSULATION MOLD for examples- Ed.

Details about the R-values and other properties of various insulation products can be found in our Insulation Table at INSULATION R-VALUES & PROPERTIES.

The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article.

  • Q&A on Cellulose Pros & Cons - PDF version, use your browser's back button to return to this page. Original article, Solar Age Magazine, December 1985/January 1986, adapted and updated for InspectAPedia.com December 2010.

The question-and-answer article above, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.


Continue reading at Cellulose Insulation Fire Resistance or select a topic from the More Reading links shown below.

Or see Cellulose loose fill insulation



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