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Community and Q&A


Andrew Thompson Zone 3a | Posted in Green Building Techniques on

Assume the following wall:

– 2x framing
– 1/2″ sheathing
– 2 layers rigid insulation (staggered seams)
– WRB (assume separate from rigid insulation)
– rainscreen strapping
– lap siding

If the air barrier is at the sheathing layer, and the water barrier is the WRB, should (need) both or either layer of rigid insulation be taped? and if so why? If experience is a guide, I’m all for over-doing-thinking everything, but alas money is finite, and fancy tapes ain’t cheap. To tape all seems like wearing a couple belts and suspenders.

Thanks in advance.

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  1. GBA Editor
    Martin Holladay | | #1

    Taping the seams of the rigid foam may improve the airtightness of the building envelope slightly, and may limit convection currents at the foam seams.

    In the type of wall you describe, these benefits will be slight, as long as you pay attention to air tightness when you seal the seams of your sheathing.

    Whether or not it's worth it to tape the foam seams is a judgment call.

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