Flash and Batt — Attic

Faulted1 | Posted in Energy Efficiency and Durability on July 24, 2011 03:24am

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?

Thanks

Answer

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jklingel | Jul 24, 2011 11:13pm | #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.
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Martin Holladay | Jul 25, 2011 08:15am | #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.
Faulted1 | Jul 25, 2011 11:08am | #3
John K.,
Yes

Martin,
2 ft wide strips?
Other suggestions...
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Martin Holladay | Jul 25, 2011 11:23am | #4
John,
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).