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Stopping exterior wall insulation at attic level with a vented attic

BuildingAHome | Posted in Energy Efficiency and Durability on

Hello, I am having 2 or 3″ of rockwool comfortboard 80 installed on my walls over zip sheathing with a 1×4 batten rainscreen over it. My house will have a vented attic assembly. I was thinking that on the walls that include a gable up to the roofline, it is a waste of the expensive rockwool material above the attic line, as there isn’t value in insulating the wall shared by my attic. Can I just stop the rockwool at this point? That would leave a 2 or 3″ void and I assume the right thing to do would be just rip and screw studs the rest of the way up the wall to continue the battens. Is having this void safe? Increased effects from wind or something living behind it comes to mind.

Thank you for any insight!

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Replies

  1. Expert Member
    MALCOLM TAYLOR | | #1

    BuildingAHome,

    The void is fine. Another alternative, if it works architecturally, is to set the wall in by several inches, and separate the two with trim and a cap flashing.

  2. rockies63 | | #2

    I would rather keep the surface of the exterior wall cladding at the same plane all the way up to the roof eaves rather than stepping it back at the gable and having to install flashing - just one more place for a potential leak.
    However, I would continue the exterior insulation to maybe 6 inches above the top of the attic floor joists and the rim board just to keep the rim board warmer and reduce thermal bridging, and then continue on above that with the vertical furring studs.

  3. Expert Member
    MALCOLM TAYLOR | | #3

    BuildingAHome,

    If as Rockie63 says there is an attic floor system, another option is to cantilever it out to make up the difference.

  4. rockies63 | | #4

    If there isn't an attic floor system and you're using trusses with the drywall attached to the bottom chord I would still run the exterior insulation up to the top of the attic floor insulation just to prevent a colder thermal bridge at the wall/ceiling juncture.

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