Choose Cellulose Over Fiberglass & Stop Mold from Getting a Hold

It’s a debate for the ages, and the perfect way to wrap up “Make Mold a Memory Month”: cellulose insulation vs. fiberglass insulation. As always, there are pros and cons to both types, but when it comes to mold-prevention, cellulose is the winner – hands down!

Earlier this month, we talked about the important role insulation plays in managing mold because of the role it plays in managing moisture. But like most things, there are exceptions to the rule. In the home insulation-as-mold-remedy discussion we have to raise the ironic point that it also possible for home insulation to act as a medium for mold growth. That’s right. There are actually situations where insulation is the CAUSE of mold. This is where the cellulose vs. fiberglass debate comes in. Let’s discuss the source of some of the confusion in the debate before we look at the facts.

The word cellulose is problematic for cellulose insulation. While cellulose is a fundamental source of nourishment for mold (this is why wood is so susceptible), cellulose insulation IS NOT a medium that is favorable to mold growth. Although it is possible for mold to grow on cellulose insulation in extreme circumstances, this would only happen in conditions such as a leak or a flood. To put this another way is to say that mold will grow in cellulose insulation but only in situations where mold would be growing everywhere else as well. Suffice it to say – cellulose insulation would not be the SOURCE of a mold problem.

The same cannot be said for fiberglass insulation. Let’s look at its makeup

  • Paper Backing (optional)
  • Glass (20-30% recycled industrial waste and post consumer product)
  • Dye
  • Resins (if there is paper backing)

In the case of fiberglass insulation, the resins and the paper backing can support mold growth, but the worst culprit is the dust that gets trapped in the fibers. The nutrients and minerals this dust provides can offer a relative smorgasbord for mold in comparison to what is happening in cellulose insulation.

Author, Jeffery C. May, who wrote “My House is Killing Me” has stated that “approximately 70% of all unfaced basement ceiling and crawl space fiberglass is severely contaminated with growing mold.”

Ironically, cellulose insulation (the insulation, which much to the chagrin of the people marketing it, is named after mold’s favorite food) does not have the same propensity for mold growth. The same author says, “In general, blown in cellulose insulation, surprisingly, is not found moldy… I have yet to see a moldy cellulose insulation sample.”

Having listed the dust as one culprit in fiberglass’s greater propensity for mold growth, logic dictates that the paper backing and the resins are guilty parties as well. Of course loose blown cellulose does not have either of these components. And there is another benefit to blown cellulose insulation on the mold front.

When we remember that mold is really a function of moisture within the envelope more than any other factor, we have to give points to blown-in cellulose insulation for its envelope sealing qualities as well.

“A University of Colorado study found that cellulose insulation cuts air infiltration 38% better than fiberglass”

In remembering that air leaking into your envelope and condensing on surfaces is the major source of moisture in the home, you begin to understand that not only is cellulose more resistant than fiberglass to mold growth – it also works to prevent the moisture that causes mold growth as well.

In terms of mold control, cellulose comes out the clear winner. It also wins on the envelope sealing, and moisture control fronts as well. And it does all this while offering superior R-values to boot! That’s a lot of reasons to favour cellulose over fiberglass.

When you consider the mold issue alone, and remember our last blog’s discussion about mold’s impact on property value, replacing fiberglass insulation – if you have it – with cellulose starts to look like a good step toward truly making mold a memory.

If you’d like to learn more about the benefits of cellulose insulation over fiberglass, an Insta-Insulation representative is standing by.

Official Insulation Contractor for Bryan Baeumler Canadian Home Builders' Association Ontario Home Builders' Association Over 10 years service with Mike Holmes

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