The house was built in 1990 with 2×6 stud walls.
It is in Climate zone 4A, about 400′ above sea level, 1/4 mile from the ocean. Latitude 49.50.
It sits on a fairly large 1/3 acre lot on a fairly steep south facing lot with full exposure on all four sides.
It is a mid sized rancher with a full basement at ground level on the south side with full 8′ foundation walls on the uphill north side.
To date the owner has redone the basement exterior drains during which 4″ styrofoam insulation was added to the exterior foundation walls.
The attic was re-insullated with two overlapping layers of 6″ Roxal, leaving the ceiling 4ml vapour barrier intact.
The basement, where developed, was completely gutted.
The plumbing was completely redone, the electric baseboards were replaced with an electric furnace with an exterior heat pump. It is a fully ducted system with both heat and air conditioning.
The main floor is freshly renovated with new floors, trim and paint.
The wall profile from the interior is 1/2′ drywall, 4ml poly, 6″ fiberglass bats, 3/8″ sheathing, tar paper and horizontal cedar siding.
The owner wants to redo the exterior siding. They want to tie the exterior styrofoam insulation into new Roxal compfortboard exterior insulation, then rainscreening and cedar siding.
My recommendation would be to cut the plywood out between the studs, to allow the 4ml poly to be removed, then reinsulate with Roxal and new 1/2 or thicker sheathing prior to adding the compfortboard, housewrap and rainscreening.
Recommendations greatly appreciated.
I feel many owners could be facing the same issues as we focus on upgrading these houses with exterior insulation.