me again. it gets cold here in philadelphia, and hot in summer. i want more insulation. my joists are 5 1/2" deep. my rafters are also 5 1/2" wide. if i put more loose fill between the joists, to the max of 5 1/2", and the max on the roof, which would be 3 1/2" batts (5 1/2 minus 2" for air space between roof and batt), will this increase my R value to whatever 9" equals? alternatively, are there any secrets for applying 12" insulation to rafters only 5 1/2" deep? hope my terms are understandable. as always, thank you.

i'm moving into an old (1910s) frame house with an unfinished attic. it currently has loose fill insulation (looks very old) between the floor joists. i'd like to put down some simple flooring so that i can use the attic for storage space (with the possibility of converting the attic into an office in a few years. my question(s) is: what are my insulation options? can i get away with just blowing new fill across the floor and covering it with plywood? or should i put insulation on the walls/ceiling before installing drywall? also, i live in a cold climate -- will blowing loose fill in the floor provide adequate insulation? are there other options i'm not considering? thanks.