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Community and Q&A

Flash and Batt — Attic

Faulted1 | Posted in Energy Efficiency and Durability on

Climate zone 4-

Goals Conditioned attic
R-50 from Foam and dense pack cellulose

Construction — Roof trusses 24″ OC

Installation preparation–

I will be adding an extra 2X4 in the truss at the necessary depth to provide a nailing surface for the Insulweb.

Can I do this at every other truss if I’m using strapping?
Do I need cross strapping perpendicular to truss chords? What spacing? 1X or 2X?

Any benefit in this particular application as to either CC or open cell foam?


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  1. jklingel | | #1

    Just so I can follow this thread.... You are spraying foam against the roof, then somehow installing Insulweb between the trusses, and dense packing between the Insulweb and the foam, right? Or am I not seeing your game plan here? Thanks.

  2. GBA Editor
    Martin Holladay | | #2

    John N.,
    I don't see how you can install InsulWeb if you are using trusses -- there are too many diagonal framing members. You need to use conventional sawn rafters for this type of roof insulation system to work.

  3. Faulted1 | | #3

    John K.,

    2 ft wide strips?
    Other suggestions...

  4. GBA Editor
    Martin Holladay | | #4

    If you frame your roof with conventional 2x10s or 2x12s, you can use InsulWeb. It's best to fur down from the rafters to create more depth; many builders do this with long 2x4s secured to the rafters with plywood gussets. The insulWeb must be securely stapled to every single framing member (every 16 inches or 24 inches).

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