Insulation question for old solid brick house
I am working on a project in Toronto and we are renovating an old brick house to bring it up to code. All the plaster and lathe has been ripped out and we are preparing to insulate the exterior walls and I would appreciate any input on the following strategy. The house is triple brick to the first floor joists then double the rest of the way. The house was built in 1919 and the brickwork looks solid.
My plan for insulation was to first, fasten DUROSPAN GPS R5 4 ft. x 8 ft. x 1.06-inch Graphite-Enhanced Expandable Polystyrene Insulation Board to the brick with construction adhesive and seal with tuck tape (R5). Next, I will construct a 2×4 stud wall overtop of the foam for electrical, plumbing, ductwork, etc. Finally, I will fill the stud wall with sprayed-on cellulose insulation (R12.3) and 1/2″ drywall (R.45). Add the two courses of brick (R.88) and my total R value will be 18.63.
Using spray foam exclusively for the exterior walls seems to be very expensive, though we will be using it for certain areas in the building. I would appreciate any thoughts you folks can throw my way.