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Community and Q&A

Perlite for walls vs Dense pack Cellulose

calvnrulz | Posted in Green Building Techniques on

Has anyone used loose fill perlite for wall cavity insulation on wood framed exterior wall. I am interested in the least toxic insulation for the walls. But I am a little concerned about the moisture retention capabilities of perlite. Does the perlite dry out quickly in a normal framed wall?

Also, does dense pack cellulose have less capacity for moisture retention?

Lastly, has anyone used loose fill perlite for attic insulation.

Climate conditions are north midwest with an average outside humidity of 72% and an indoor humidity set at 50%. Reg D temp is 90 and 2 fahrenheit.

Lastly, in the alternative, is there any experience with foam applied to the outside of OSB on exterrior walls with no wall cavity insulation.


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  1. GBA Editor
    Martin Holladay | | #1

    If I were you, I wouldn't worry about the toxicity of cellulose insulation. Reports of reactions to cellulose insulation are extremely rare.

    Perlite won't perform as well as cellulose insulation in a wood-framed wall, for a variety of reasons (including the fact that it won't do as good a job of reducing air leakage as cellulose). If you want to read more about how perlite is actually used on job sites, see this web page: Perlite as Insulation.

    Another important factor: You won't be able to locate a contractor willing to experiment with perlite in wood-framed walls.

    Attaching rigid foam to the exterior side of wood-framed walls without installing any insulation between the studs is a common and time-tested approach. The method is called PERSIST. For more information on the PERSIST approach, see Getting Insulation Out of Your Walls and Ceilings.

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