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Community and Q&A

Air sealing existing house – major reno

GBA Editor | Posted in Energy Efficiency and Durability on

We’re embarking on a new project, stripping off the siding and adding several inches (4-6″) of polyiso to the exterior. We’d like to be able to do a blower door test before we add the rigid to make sure we’ve done a good job air-sealing. The existing, for the most part, is a post & beam frame with 2x infill framing, plywood sheathing (looks like 1/2″ CD or CDX) and then 1″ of EPS covered with 1x ship-lap pine. Plan is to use some kind of housewrap, full coverage ice & water on the roof, presumably some gasketing or spray foam will be necessary at the sill. Anyone have any clever ideas for products or methods?

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  1. GBA Editor
    Martin Holladay | | #1

    If you are concerned about air sealing, as you should be, then you should include a bead of caulk under the perimeter of the polyisocyanurate layer (at the base of the wall and the corners of the house, as well as around each window and door). Use a high-quality housewrap tape at each polyiso seam, for both layers of polyiso. Stagger your polyiso joints.

    Think about your intersections -- around windows, and at the intersection of the wall and the roof. If you're using Ice & Water Shield as your roof air barrier, be sure that the seam between the Ice and Water Shield and the polyisocyanurate on the walls has been air sealed.

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