I'm interested in replacing my inadequate 35 year old fiberglass insulation in my attic with blown in cellulose. What i'm trying to figure out is how many bags I need. I want R-50, which comes out to 15" (right?). I have 1344sqft of attic floor space. The insulation is here and it says it's 2.2cuft. I'm assuming that's 2.2cuft compressed in the bag. How many cuft would it be once it's blown in... so I can figure out the number of bags?