Add that the house will be 3000 sf & 1.5 stories.

Add that we will be using Heat pump & gas.

go to hvac-talk.com
there is a guy there who has
the screen name of Teddy Bear.
that is who I'd talk to.
put his name in the subject posting
line.

he will recommend a whole house
dehumidifier with ducted fresh air.
but he can explain the ins and outs
much better than I.

good choice to put foam in rafters,
just make sure it meets code R-value
requirements. open cell is about R-4.2 per
inch, so the inches/r-value HAS to meet
code. 3" does not perform as R-30.

for walls, putting foam sheathing to exterior
(rigid extruded polystyrene), taping all seams
and holes, and sealing sole plate to slab will
make wall air tight to interior. proper flashing
of doors windows and all exterior pentrations..including
framing will complete exterior air sealing.
use convnetional insulation in walls and air
tight drywall approach to interior. save the
foam insulation for walls money to invest in
other areas.

go to buildingscience.com & search for 'perfect wall'
construction. while I've recommended this for years
based on what works here in La. and the cost/verified
install side of new homes, this is according to
building science sites a wall that works in all
climates. sure pays back quicker than foam inside of
walls.

best of luck.