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Community and Q&A

Catheralized attic insulation upgrades

Scott Kutylowski | Posted in Green Building Techniques on

I have a new energy star rated home, HERS score of 60. The builder installed blown in cellulose insulation into a netting at the underside of the tile roof. (R-22) This is a non vented attic with Cathedralized attic insulation. The home is located in a Phoenix suburb. Is there a way to upgrade the insulation? Can I add spray form over the top of the cellulose and the wood trusses to stop thermal bridging? Can have insulation added to the attic floor?

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  1. GBA Editor
    Martin Holladay | | #1

    Q. "Can I add spray form over the top of the cellulose and the wood trusses to stop thermal bridging?"

    A. I don't see how you could do that -- I assume that the concrete roofing tiles have already been installed. Right?

    Phoenix is in Climate Zone 2. The 2012 International Residential Code requires a minimum of R-38 ceiling insulation in Climate Zone 2, so I'm surprised that your Energy Star home has only R-22 insulation. That's not much.

    Is the existing cellulose insulation protected on the interior with drywall? Or is the netting visible when you stand in the attic? It sounds to me as if the insulation system installed in your attic might resemble the Owens Corning ProPink High Performance Conditioned Attic System -- except using cellulose instead of fiberglass. (I wrote about that insulation system in a blog titled Can Unvented Roof Assemblies Be Insulated With Fiberglass?)

  2. Scott Kutylowski | | #2

    The netting / insulation is visible from inside the attic, I have 9 foot flat ceilings. Can I blow in cellulose on top of the ceiling? The cellulose is blown into netting that is stapled to the underside of the roof. I kind looks like pillows between the top cords of the trusses. I would like to overlay spray foam on the cellulose netting to increase the R-value. The local insulation contractor does not have any recommendations other than to remove the tile roof and install foam board on top of the roof and re-install the tiles.

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