Hi,
We’re considering a PGH approach for our 2.5 story 1876 masonry building. For a variety of reasons, we’re considering starting the work late Summer on the 2nd (full) and 3rd (1/2) flrs. We’re in Chicago and have a flat roof over the 2nd floor, and a cathedral on the 3rd. We’ll build up the flat roof with exterior rigid insulation, and blow-in insulation in the cavity below, and in the cathedral portion of the 3rd floor. We’re planning to remove plaster lathe on 2nd and 3rd floors, and frame the interior walls to insulate. We’ll do air sealing throughout the entire house. My question, what type of risks are we creating to have insulation on top portion of building, and non-insulated walls on foundation and first floor? I’m worried this detail might create some temperature gradient issues that damage masonry, or cause moisture damage inside.