AtticCare

the feds recommend r49 for all but very southern georgia and its still r38 there, you probably average 11-12inches which is just a around the new home requirements of r30, some retailers where you get the "pink stuff" will let you borrow the machine with insulation purchase, you will need 10-12 bags per 1000ft2 im gonna guess 300$ worth, you need the machine to fluff the insulation otherwise the r value will suck, if your gonna track the existing insulation to add a bag your probably gonna end up worse off then ya started. before you do all of this check for air leaks in your ceiling by looking for dirty spots, and make sure it is properly ventilated...........just spend the 300-400 bucks per 1000ft2 and youll probably get it back in the first year or two.... answer in the small version..... no dont buy a bag of loosefill and throw it in, it probably says not to and why on the bag

AtticCare

Its an old topic but i think that it needs to be addressed that unless you aggitate the loose-fill fiberglass, it wont achieve its r-value. Also a comment on fiberglass not having good r-value?? Not true, you can blow r-60 fiberglass. And dont be sure about cellulose being fireproof, its is fire retarding, which is different, basically meaning it will smolder for so long and then, POOF

joecaption

They should have all been IC air tite. If not there all leaking cold air into the house.
Dumping more insulation in the low spots will do no harm.
http://www.checkthishouse.com/4417/how-much-attic-insulation-you-need-insulation-zone-map.html