I am starting from a "raw" attic - NO INSULATION. I want to build rooms in the attic, but want to make sure that I don't over-insulate. Do I insulate the inside living cavity, leaving the roof exposed to breathe or do I insulate between the roof joints with vapor barrier (3 breather vents) & breather chutes within the channels or do I do a combination. Right now it's 140 degrees up there in the summer & below zero in the winter in this 1925 brick bungalow.
Treat the attice as a regular floor in the house. No insulation below and insulate above. Make sure that the insulation above "breathes" or else ou will get condensation in the winter. Ideally you can provide for ridge and soffit vents to allow outside air to circulate behind the insullation. Don't over-stuff the rafter cavity. Possibly take a look at foam insulation nailed to the rafters and then covered with drywall. That will allow good breathing space behind and open the possibility of notching the rafter to allow cross circulation in the event that a ridge vent isn't feasable and you have to go with power vent or gable vent