Do I need to be concerned with insulating the attic?
Will insulating the attic cause moisture buildup behind the walls?
Will I need to install soffit vents to prevent moisture buildup since originally the house does not have soffit venting?
Should I use faced or unfaced insulation?
And what is this 1 inch minimum air space requirement that I keep reading about?
It won't cause moisture buildup if you install a vapor barrier on the warm side (inside if you're in the north, outside if you're in the south).
Soffit vents only work if you have a ridge vent, gable vents, or rooftop vents to exhaust the air they bring in.
You will have to install venting.
The one inch air space refers to keeping the insulation one inch away from the shealthing. Otherwise, your soffit vents will not work. They operate by bringing in air, which rises through that inch of air space, cooling off the roof deck as it passes, and exits at the ridge or gables.
