Sealing new wall to old wall intersection

I’m re-building an addition to an old house. The exterior wall of the addition T’s off the existing structure as in the attached sketch.A couple of challenges: 1. The existing structure… I’m re-building an addition to an old house. The exterior wall of the addition T’s off the existing structure as in the attached sketch.A couple of challenges: 1. The existing structure…Read MoreGreenBuildingAdvisor