My guess on what i would need to do.
How to conditioned attic space.
Require air sealing and air barriers including attic hatches flues piping lighting wiring chases attic eaves dropped ceilings and knee walls.
At least half of your attic space must be 7 feet high by 7 feet wide with a total of 70 square feet.
Hire a pro to install spray foam insulation.
Making the attic a conditioned space taking the building envelope to the roof is a good approach and will save energy another approach is to use radiant coated deck sheathing seal all ceiling attic penetrations and blow in r 60 insulation as it will cost less than spray foam and should give at least the same energy efficiency to the home.
This might entail encapsulating the foam with roofing on the top and sheetrock on the underside of the foam.
Close the connection between attics with a door since i may still need access to that new attic.
You can use rigid foam panels or do as tom silva does with nearly all houses these days.
Pull down stairs won t work for an attic room so you must add a permanent staircase.
But you may plan to finish the room for living space.
If you re considering turning your attic into conditioned storage or living space it s worth changing tactics to insulate between the rafters and wall joists instead of the floor.
Put hard foam pink stuff in between the beams im just not sure how to keep it on the roof.
In warmer climates unvented attics can prevent the condensation that occurs on ductwork in some vented attic spaces.
The loss of conditioned air increases heating and cooling demand.
A design decision to have a central ducted heating and cooling system with ducts and air handler located in the attic is another good reason to insulate and air seal at the roof line which will provide a conditioned or semi conditioned space for the hvac equipment.
Codes vary from place to place but the rule of 7 for using an attic as an actual room typically applies.
If you planned to leave the open cell foam exposed to the attic it would certainly dry to the inside much more easily.
The loss of energy efficiency means some designers choose to move the ductwork into the conditioned areas of the home and leave the attics unvented.
Humid indoor air that escapes into the attic can.